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Open-loop geothermal - well problems LONG POST

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Open-loop geothermal - well problems LONG POST Reinhard 08-07-2007
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Posted by Tony on August 10, 2007, 1:18 pm
Gave you something to think about

>
>>I have very interesting proposal for you
>>pull you pipe lines out of well if any
>>now shove stick of delamite in to well
>>"fire in hole"
>>that will open the hole and you may get
>>even the oil out of it. "You never can tell"
>>on the other hand I would take Bobs advice
>>Tony
>>
> Good GAWD-a-mighty, Tony.
> What in the hell language are you speaking?
> Are you "free-basing" or "speed-balling" or whatever the hell?
> Bubba
>
>
>>>I have a new house with an open-loop geothermal system. The house is two-
>>> storey with two heat pumps; a 5 ton unit for the first floor, basement
>>> and crawlspace and a 3 ton unit for the second floor. Used since last
>>> fall. Got great heat in winter with no red lights for the auxiliary
>>> heat,
>>> even on coldest windy nights (-35 degrees Celsius). Cools even better in
>>> recent heat wave (35 degrees Celcius). I am in Winnipeg, Canada where it
>>> gets pretty cold but only gets very hot for a few weeks.
>>>
>>> I have two problems, perhaps partly related.
>>>
>>> Most serious is that the injection well was overflowing by the end of
>>> winter. Normal static level is about 25 feet down casing with about 8
>>> foot rise when both units are running. When it overflowed I could see
>>> that there were a lot of bubbles, more than a pot at full boil.
>>>
>>> My pump rate is 21 USgpm.
>>>
>>> The bubbles were caused by pressure reducing valves (PRV's) that were
>>> installed downstream of each unit. When I cranked the PRV's wide open
>>> the
>>> bubbles stopped and then came back when I reset the PRV's. I did this
>>> several times and definitely isolated the bubbles to the PRV's.
>>>
>>> I was told that the PRV's were necessary because the installers adjusted
>>> the flow rate through each unit to limit the leaving water temp to 38
>>> degrees F so that there would be no risk of freezing the exchangers.
>>> This
>>> seems exactly incorrect to me since slowing down the flow would allow
>>> the
>>> unit to draw more heat from each gallon of water and thus reduce the
>>> leaving water temp. To prevent freezing you should speed up the flow so
>>> each gallon gives up less heat and the leaving water temp would be
>>> higher.
>>>
>>> The bubbles air locked the well, at least part of the problem was solved
>>> by installing a pump down the injection well and pumping out for a
>>> while.
>>> Then going back to the main house pump in injection mode. A lot or air
>>> was discharged, quite violently, from the well. A few cycles of this and
>>> I solved most of the problem - the mound up is 2 or 3 feet higher than
>>> last summer.
>>>
>>> I don't know if the remainder of the capacity loss is more air in the
>>> formation that I can't get out or possibly calcium or iron precititation
>>> partially plugging the limestone formation. I acid treated these wells
>>> after they were installed and that really increased the capacity so I
>>> can
>>> always do that again.
>>>
>>> The wells are both open holes in limestone formations, no screens at
>>> all.
>>> Sometimes I get a small amount of sand plugging the filter in the
>>> basement but not much - about a tablespoon of sand once every 3 to 6
>>> months. When I get the sand I just run the main pump on high to a pipe
>>> to
>>> the river for a few hours and the sand goes away for a few months. I may
>>> have to borrow a larger pump so I can over-pump the well to get rid of
>>> more of the sand. It's not the main problem anyway.
>>>
>>> My biggest problem is iron bacteria infection. I have been getting red
>>> slime on the filter to the extent that I have to clean it every 2 to 4
>>> weeks. I have also learned that the bubbles could have caused both iron
>>> and calcium to precipitate out of solution. The water tested high for
>>> calcium hardness and maxed the iron bacteria colony counts.
>>>
>>> I have researched well disinfection both from local experts and internet
>>> googling. I learned that the infection usually comes back. I figure that
>>> is because the methods used for domestic water wells are not adequate,
>>> or
>>> more accurately not enough, for geothermal open-loops. Since we have
>>> been
>>> pumping for a year now the bacteria has been spread through the
>>> limestone
>>> formation between the wells. Testing shows a 4-inch drop at one well
>>> when
>>> pumping the other well and discharging to ground. This is a good dis-
>>> connection from the point of view of geothermal heating or cooling but
>>> any connection at all will lead to spreading the infection. So I figure
>>> that the reason the infections always return may be that you have to
>>> disinfect the whole flow path between the wells to get all of the
>>> bacteria. If you just disinfect each well then as soon as you go back to
>>> normal operation you will suck the bacteria that were out of range of
>>> the
>>> chlorine into the system and you are back at square one.
>>>
>>> I am thinking of siphoning chlorine into the discharge pipe in the
>>> injection well for two weeks or so. This should get chlorine into the
>>> flow path between the wells and hopefully solve the problem once and for
>>> all. My concern is that I calculate the chlorine ampount as over $1500
>>> for just 50 to 100 ppm, more for the higher concentrations.
>>>
>>> Has anyone done any well disinfection? If so, was it successful and, if
>>> so, what did you do?
>>



Posted by on August 9, 2007, 7:37 pm
> I have a new house with an open-loop geothermal system. The house is two-
> storey with two heat pumps; a 5 ton unit for the first floor, basement
> and crawlspace and a 3 ton unit for the second floor. Used since last
> fall. Got great heat in winter with no red lights for the auxiliary heat,
> even on coldest windy nights (-35 degrees Celsius). Cools even better in
> recent heat wave (35 degrees Celcius). I am in Winnipeg, Canada where it
> gets pretty cold but only gets very hot for a few weeks.
>
> I have two problems, perhaps partly related.
>
> Most serious is that the injection well was overflowing by the end of
> winter. Normal static level is about 25 feet down casing with about 8
> foot rise when both units are running. When it overflowed I could see
> that there were a lot of bubbles, more than a pot at full boil.
>
> My pump rate is 21 USgpm.
>
> The bubbles were caused by pressure reducing valves (PRV's) that were
> installed downstream of each unit. When I cranked the PRV's wide open the
> bubbles stopped and then came back when I reset the PRV's. I did this
> several times and definitely isolated the bubbles to the PRV's.
>
> I was told that the PRV's were necessary because the installers adjusted
> the flow rate through each unit to limit the leaving water temp to 38
> degrees F so that there would be no risk of freezing the exchangers. This
> seems exactly incorrect to me since slowing down the flow would allow the
> unit to draw more heat from each gallon of water and thus reduce the
> leaving water temp. To prevent freezing you should speed up the flow so
> each gallon gives up less heat and the leaving water temp would be
> higher.
>
> The bubbles air locked the well, at least part of the problem was solved
> by installing a pump down the injection well and pumping out for a while.
> Then going back to the main house pump in injection mode. A lot or air
> was discharged, quite violently, from the well. A few cycles of this and
> I solved most of the problem - the mound up is 2 or 3 feet higher than
> last summer.
>
> I don't know if the remainder of the capacity loss is more air in the
> formation that I can't get out or possibly calcium or iron precititation
> partially plugging the limestone formation. I acid treated these wells
> after they were installed and that really increased the capacity so I can
> always do that again.
>
> The wells are both open holes in limestone formations, no screens at all.
> Sometimes I get a small amount of sand plugging the filter in the
> basement but not much - about a tablespoon of sand once every 3 to 6
> months. When I get the sand I just run the main pump on high to a pipe to
> the river for a few hours and the sand goes away for a few months. I may
> have to borrow a larger pump so I can over-pump the well to get rid of
> more of the sand. It's not the main problem anyway.
>
> My biggest problem is iron bacteria infection. I have been getting red
> slime on the filter to the extent that I have to clean it every 2 to 4
> weeks. I have also learned that the bubbles could have caused both iron
> and calcium to precipitate out of solution. The water tested high for
> calcium hardness and maxed the iron bacteria colony counts.
>
> I have researched well disinfection both from local experts and internet
> googling. I learned that the infection usually comes back. I figure that
> is because the methods used for domestic water wells are not adequate, or
> more accurately not enough, for geothermal open-loops. Since we have been
> pumping for a year now the bacteria has been spread through the limestone
> formation between the wells. Testing shows a 4-inch drop at one well when
> pumping the other well and discharging to ground. This is a good dis-
> connection from the point of view of geothermal heating or cooling but
> any connection at all will lead to spreading the infection. So I figure
> that the reason the infections always return may be that you have to
> disinfect the whole flow path between the wells to get all of the
> bacteria. If you just disinfect each well then as soon as you go back to
> normal operation you will suck the bacteria that were out of range of the
> chlorine into the system and you are back at square one.
>
> I am thinking of siphoning chlorine into the discharge pipe in the
> injection well for two weeks or so. This should get chlorine into the
> flow path between the wells and hopefully solve the problem once and for
> all. My concern is that I calculate the chlorine ampount as over $1500
> for just 50 to 100 ppm, more for the higher concentrations.
>
> Has anyone done any well disinfection? If so, was it successful and, if
> so, what did you do?

I have a Waterfurance 072 spit system vertical loop, which has never
worked. I'm not saving any money going Geo, You, will get alot of
advice here on this group, just as I did. it's going to cost $$$$$$$$
$$$$
Regards and good luck, RT


Posted by Reinhard on August 9, 2007, 11:05 pm
Thanks, guys, for your coments. I agree with all of you.

I'm stuck with the open-loop system because the house is on a riverbank
that is clay so it is not that stable. A closed loop system, either
horizontal or vertical, would be in danger of getting torn apart with the
movements of the bank. Piping to the river would not be allowed because
we are not allowed to discharge anything into our rivers up here.

The aquifer is not potable water because it is way too salty so I didn't
even need to get a permit for the two wells, part of that was also
related to not being a net user of water - changing the temp is OK as
long as you don't use any water.

I have narrowed the capacity problem down to the bubbles caused by the
PRV's. I'll have the installer remove the PRV's which will prevent the
problem from re-occurring. Then I'll acid treat the injection well to get
it's capacity back to normal. I did the acid treatment myself when the
wells were originally drilled so I know how to do it and I'll only be out
the cost of the acid.

I am a civil engineer specializing in water resources so doing the well
work is not too tough. I also was the general contractor on the house so
I am actually in charge of my own warranty work. The original heating
contractor turned out to be a crook - stealing from us and everyone else
in town - so I had to fire him after he had drilled the wells but had not
yet installed the well pump or heat pumps. Only got robbed of about $2500
which was actually good for the horror stories this guy left behind when
he ran out of town. I then contracted with a great geo company to install
the heat pumps and finish the ducting, etc but they didn't want any part
of the well work this guy had started so I am responsible for that
portion myself.

My real problem is disinfecting the wells in a way that will solve the
problem once and for all. My best idea is to first disinfect both wells
in the usual fashion and then inject chlorine into the discharge line for
about 2 weeks. My theory is that the chlorine will follow the flow path
through the limestone formation and kill all of the iron bacteria so it
won't come back. That takes quite a bit of chlorine which I estimate to
cost at least $1500 but could be double or triple depending on how high a
concentration I need to use. I was hoping someone here had some
experience chlorinating open-loop geothermal wells which is quite
different from simple domestic water supply wells. With a domestic well
chlorine costs from $2 to $6 if you want to go overboard. I need at least
1,000 gallons of Javex to get enough chlorine for the minimum chlorine
concentration and I am not sure if the minimum will accomplish anything
at all.

Questions I have are what concentrations have worked for others. Chlorine
is less effective at cooler temps which is just what I have underground.
Also, my PH is just at the max for best chlorine effectiveness and
reducing PH with acid would help. Bit risky as mixing chlorine with acid
can result in dangerous gases but I have all the safety equipment and it
doesn't take much acid to lower PH.

Soner or later I'll get this system debugged. Last winter the system
delivered all the heat we needed. In the middle of 40 below nights with
very high winds I got up several times to see if the auxiliary heat had
cut in and it hadn't. So the heat pumps were delivering well above their
design capacity. This past month we have had 35 degree Celcius heat waves
and the house was simple to cool. I used R20 walls, R60 ceilings, triple
pane windows with all the E features and R2000 level sealing so the house
is very energy efficient. The heat pumps are ClimateMasters with multi-
stage scroll compressors which are about as high efficient as it gets. It
is a 5,000 square feet house and we are using about $3,300 all up for
electricity for a year - heating, cooling, hot tub, 4 computers, 2 ovens,
pretty much all the toys. I figure the geo is worth the hassles.

I just need to solve the iron bacteria problem. If I had a bit of
guidance on the concentrations it would be a great help. Spending that
much money on chlorine is bad enough but if I try to save money by going
light on the concentration then I just waste all of it. Going too high if
unecessary, costs $1,000 to $3,000 extra so guessing is nervewracking.

Posted by Geoman on August 10, 2007, 9:20 am

>I have a new house with an open-loop geothermal system. The house is two-
> storey with two heat pumps; a 5 ton unit for the first floor, basement
> and crawlspace and a 3 ton unit for the second floor. Used since last
> fall. Got great heat in winter with no red lights for the auxiliary heat,
> even on coldest windy nights (-35 degrees Celsius). Cools even better in
> recent heat wave (35 degrees Celcius). I am in Winnipeg, Canada where it
> gets pretty cold but only gets very hot for a few weeks.
>
> I have two problems, perhaps partly related.
>
> Most serious is that the injection well was overflowing by the end of
> winter. Normal static level is about 25 feet down casing with about 8
> foot rise when both units are running. When it overflowed I could see
> that there were a lot of bubbles, more than a pot at full boil.
>
> My pump rate is 21 USgpm.
>
> The bubbles were caused by pressure reducing valves (PRV's) that were
> installed downstream of each unit. When I cranked the PRV's wide open the
> bubbles stopped and then came back when I reset the PRV's. I did this
> several times and definitely isolated the bubbles to the PRV's.

Did they install the PVR's on the outlet or inlet of the pumps? The inlet
side of the pumps will cause massive cavitation.
Better to use a variable speed pump and adjust it to the proper GPM

>
> I was told that the PRV's were necessary because the installers adjusted
> the flow rate through each unit to limit the leaving water temp to 38
> degrees F so that there would be no risk of freezing the exchangers.

Adjusting flow rate are for several reasons.
To maintain refrigerant pressures withing design conditions, too much water
and your refrigeration pressures go too high or too low for their designed
conditions. The flow rate is determined by water temp and capacity of the
unit. Flow rate adjustment is also important to help prevent deposit
formation and to help prevent errosion of the exchanger.
If you have too many gpms in the summer you may experience possible icing on
the air side evap coil due to the capacity of the compressor becoming much
greater in BTU's than what your evap and CFM 's are capable of removing,
this is expecially true with an FCCV or Cap tube system. You can also
experience short cycling due to low inside evaporator pressures. The
isntallers were correct but its not icing on the water side but the air
evaporator side. In Heating mode the air discharge temps on the air side
could be increased with more GPM's but it could be at a cost, errosion and
compressor stress.

If you have even seen a geo with Penn water valves that are oversized you
would immediatly know what I'm speaking of, and you don't want that problem.


This
> seems exactly incorrect to me since slowing down the flow would allow the
> unit to draw more heat from each gallon of water and thus reduce the
> leaving water temp. To prevent freezing you should speed up the flow so
> each gallon gives up less heat and the leaving water temp would be
> higher.

>
> The bubbles air locked the well, at least part of the problem was solved
> by installing a pump down the injection well and pumping out for a while.
> Then going back to the main house pump in injection mode. A lot or air
> was discharged, quite violently, from the well. A few cycles of this and
> I solved most of the problem - the mound up is 2 or 3 feet higher than
> last summer.

Variable speed pump may solve this. Also, put a restriction on the outlet
side of the tube running into the receiving well, it doesn't have to be a
big restriction. This will help with the bubbles. Make sure you prove your
gpms. The water coming out of the restriction at the end of the pipe would
normally cause bubbles, but when its at the 25 ft depth it usually does not
due to the pressure at 25 feet. What happening now is your creating bubbles
due to lack of pressure at the PVR, lets say 25PSI to atmosphere, which
agravates the bubble situation, restriction at the 25 depth limits the
amount of pressure difference.

PLEASE LET US KNOW IF THIS WORKS, I need the information for my book.


>
> I don't know if the remainder of the capacity loss is more air in the
> formation that I can't get out or possibly calcium or iron precititation
> partially plugging the limestone formation. I acid treated these wells
> after they were installed and that really increased the capacity so I can
> always do that again.


Have you considered going deeper on your well and finding two aquafers, one
on top of the other? With this system you would pump from the bottom and
return on the top. This is done quite extensively in Virginia. But with
limestone you must have a deep well.

BTW, capacity lose in your unit will probably happen soon due to scale build
up.
Bacteria is happening due to oxygenization of the water, cant get away from
it. You can use an ozone generator made for water but its not cheap to
purchase.

>
> The wells are both open holes in limestone formations, no screens at all.
> Sometimes I get a small amount of sand plugging the filter in the
> basement but not much - about a tablespoon of sand once every 3 to 6
> months. When I get the sand I just run the main pump on high to a pipe to
> the river for a few hours and the sand goes away for a few months. I may
> have to borrow a larger pump so I can over-pump the well to get rid of
> more of the sand. It's not the main problem anyway.
>
> My biggest problem is iron bacteria infection. I have been getting red
> slime on the filter to the extent that I have to clean it every 2 to 4
> weeks. I have also learned that the bubbles could have caused both iron
> and calcium to precipitate out of solution. The water tested high for
> calcium hardness and maxed the iron bacteria colony counts.
>
> I have researched well disinfection both from local experts and internet
> googling. I learned that the infection usually comes back. I figure that
> is because the methods used for domestic water wells are not adequate, or
> more accurately not enough, for geothermal open-loops. Since we have been
> pumping for a year now the bacteria has been spread through the limestone
> formation between the wells. Testing shows a 4-inch drop at one well when
> pumping the other well and discharging to ground.

Yes, eventually your well will dry up due to plugging of the system with all
this bacteria building up.

I would suggest two things. First, you mention that you cant put a loop in
due to shifting of the banks. But your home is on this property, aren't you
afraid of it slidding into the river? I'm sure you can put your horizontal
loop somewhere. Loop material is tougher than you think, what about your
water lines undergroud etc.

Go vertical, your well is vertical, It will cost a lot of money for 8 tons
but, heck, no offence, your an engineer...

Lastly, if your not in a very populated area put the darn thing in the
river. First try to explain to the jerks who are incharge that you are NOT
discharging into the river anything that didn't come out of it. Tell them
you will actually help it by oxygenating it and you will have the water
filtered, thus its going back CLEANER than what you took out! If they say
no, wait until there is a shift in power and do it underground and thumb
your nose at them. Its obvious their idiots so you play the "I didn't know'
argument if something develops. Of course, you best check out what the
penalties are, in Canada you may have to be castrated for such an offence~

Keep in touch

This is a good dis-
> connection from the point of view of geothermal heating or cooling but
> any connection at all will lead to spreading the infection. So I figure
> that the reason the infections always return may be that you have to
> disinfect the whole flow path between the wells to get all of the
> bacteria. If you just disinfect each well then as soon as you go back to
> normal operation you will suck the bacteria that were out of range of the
> chlorine into the system and you are back at square one.
>
> I am thinking of siphoning chlorine into the discharge pipe in the
> injection well for two weeks or so. This should get chlorine into the
> flow path between the wells and hopefully solve the problem once and for
> all. My concern is that I calculate the chlorine ampount as over $1500
> for just 50 to 100 ppm, more for the higher concentrations.
>
> Has anyone done any well disinfection? If so, was it successful and, if
> so, what did you do?



Posted by Reinhard on August 11, 2007, 8:41 pm

THANK-YOU VERY MUCH, GEOMAN !!! I do believe I've got it!

All of the points you made were great; I've done most of them.

You made a super comment which twigged my mind to the solution I was over-
looking all along. You suggested an ozone generator which I had not thought
of. I am afraid of using ozone because it makes bubbles which will air-lock
my well again. BUT it made me think of salt water chlorine generators -
same thing only different. I have been researching them for a swim-in-place
pool I made in the basement but haven't finished yet. I did my own design
and had the thing poured by the foundation contractor when we did the
basement. I haven't finished my pump system design and want to use a
chlorine generator instead of dumping in chemicals - supposed to be a
different chlorine ion which doesn't smell or irritate eyes, etc. Anyway
our groundwater has a high salt content, more than enough for the
generators. I was going to use well water for the pool and call it a salt
water spa. It works great in the hot tub. Anyhow - chlorine generation will
let me get a continuous source of chlorine for free, after the cost of the
equipment. The well work can make do with a simpler generator because it
doesn't need sensors to turn it on or off. It will run whenever the well
pump is running. It can be run forever to keep any new bacteria from
multiplying. I just need to find out what concentration these things crank
out. Hope I don't have to get a massive one. I estimate the chlorine to
cost from $1500 to maybe $4500 and the fancy chlorine generator for the
pool is only $1500 with all the bells and whistles. I saw a cheap one
advertised for $269 - it the thing made a high enough concentration and
lasted a few weeks I would be done and money ahead. Only one question I
need to research - do these things make bubbles, too? I'll try my Yahoo
pool users group.

Would you know if I should run the chlorine through the heat pumps or plumb
it in downstream? I thinking downstream so I don't corrode the expensive
bits if I over-do the chlorine to kill the bacteria. Might be nice to clean
out the equipment and keep it clean. Maybe plumb it in a parallel fashion
so I can skip the heat pumps for the initial high concentration phase and
then dial down the chlorine and run it through the heat pumps to keep them
clean. Would the chlorine yield any benefits such as scale reduction? My
water coils are cupro-nickel because of the salty water. Don't know how
that relates to chlorine though.
>
> Did they install the PVR's on the outlet or inlet of the pumps? The
> inlet side of the pumps will cause massive cavitation.
> Better to use a variable speed pump and adjust it to the proper GPM

PRV's are on the outlet side of the heat pumps. They cause massive
cavitation there, too. BTW, cavitation is not the correct engineering term.
Cavitation refers to velocities much higher than in geo systems and it
leads to erosion of strong metals. What we have is release of dissolved air
and/or carbon dioxide due to the low pressures in the valves. Pressure and
velocity are inversely related - if one rises the other drops. So a large
increase in one leads to a large decrease in the other. Also, pressure is
related to velocity squared so high velocities can quickly lead to very low
pressures.

>
> Adjusting flow rate are for several reasons.
> To maintain refrigerant pressures withing design conditions, too much
> water and your refrigeration pressures go too high or too low for
> their designed conditions. The flow rate is determined by water temp
> and capacity of the unit. Flow rate adjustment is also important to
> help prevent deposit formation and to help prevent errosion of the
> exchanger. If you have too many gpms in the summer you may experience
> possible icing on the air side evap coil due to the capacity of the
> compressor becoming much greater in BTU's than what your evap and CFM
> 's are capable of removing, this is expecially true with an FCCV or
> Cap tube system. You can also experience short cycling due to low
> inside evaporator pressures. The isntallers were correct but its not
> icing on the water side but the air evaporator side. In Heating mode
> the air discharge temps on the air side could be increased with more
> GPM's but it could be at a cost, errosion and compressor stress.

This is great to know because I really like and respect the installers and
am happy to know they were on the right track all along. They gave me a
high level of confidence in their work and now you have helped me get back
to that good feeling. I'll pass this on to them, if you do't mind.
>
> Variable speed pump may solve this. Also, put a restriction on the
> outlet side of the tube running into the receiving well, it doesn't
> have to be a big restriction. This will help with the bubbles. Make
> sure you prove your gpms. The water coming out of the restriction at
> the end of the pipe would normally cause bubbles, but when its at the
> 25 ft depth it usually does not due to the pressure at 25 feet. What
> happening now is your creating bubbles due to lack of pressure at the
> PVR, lets say 25PSI to atmosphere, which agravates the bubble
> situation, restriction at the 25 depth limits the amount of pressure
> difference.
>
> PLEASE LET US KNOW IF THIS WORKS, I need the information for my book.

I had 75 feet of discharge pipe to start (50 feet below static water level)
and figured the depth might limit bubble formation, and maybe it did limit
new bubbles from forming at the end of the discharge pipe but it did
nothing for the many bubbles formed by the PRV's. Even back pressuring with
a smaller discharge pipe did not stop the extreme hissing and bubbling from
the PRV's. Maybe a liitle but barely noticeable.

I do have a variable speed pump - Grundfos 22SQE07-160 to be exact. Also, I
have the C301 controller for this pump. My geotechnical engineer friend has

also recommended a restriction on the end of the discharge pipe. He has
added restrictions to a lot of client wells and it has solved their air-
locking problems. I am using a slightly different variation - instead of a
restrictor orifice I am using a long piece of down-sized pipe. The small
pipe will cause the same restriction as an orifice ( I pick size and length
that way) by friction loss but it has a larger flow area and therefore
lower velocities and less chance of bubbles. Same pressure change just a
different method.

I have added a 50 foot piece of 3/4 inch pipe, replaces 75 feet of 1.5
inch. This does pressurize the system a lot better and lets me run the pump
a bit slower. I am re-computing my system head curves more accurately than
I had before to get a better handle on the exact discharge pipe size and
length. I had actually sized my system for a smaller Grundfos pump than the
one I have and I don't remember why I have the larger one - probably a
problem with supply and I was in too much of a hurry to wait for the other
one - rings a bell. My new computations show that I have been getting
around 27 to 30 gpm compared to the manufacturers recommended 21 gpm -
before my 3/4 inch pipe but with the PRV's.

The Grunfos controller has a lot of great features but it has one hassle
for me. It shows the current draw, in watts, for the well pump plus speed,
temp, pressure, etc. I was running 1300 watts all winter with the PRV's
and when I opened them up and added my 3/4 inch pipe I found that I could
get all the flow I needed at 650 watts ro so. Trouble is the shut-off
pressure at that speed is only 27 psi. The Grundfos controller has a lowest
setting of 40 psi so I can't set it low enough to shut off the pump when
both heat pumps have shut their valves. The pump has a regular speed of
10,700 rpm (this is a 3-inch diameter pump) and I can slow it to 9400 rpm
and run about 850 watts which is a significant improvement. I want to add
more restriction to the discharge pipe which should back pressure the
system enough to slow down the pump flows some more - still too high for
the 50 foot 3/4 inch. I think a 100 foot of 3/4 inch should do it but I
haven't finished my computing yet. I should end up with the 21 gpm flows at
9400 rpm and hopefully less than 800 watts. The controller shows the
instantaneous power draw as well as the total power used by the pump since
new - like a car odometer, it can't be reset. The well pump didn't use a
lot of power even at the 1300 watts all year. I really like the Grundfos
controller except for the minimum shut off setting issue. I guess they make
it for domestic water supply where that would be perfect. Also, you have to
pay extra for a remote control which is the only way to set or change
anything except for the shut off setting. If I loose or break the
controller I won't be able to reset anything at all. Also, there is a wide
strip wire inside the unit which blocks the infra-red signal so I have to
leave the cover semi-open to use the remote. Pretty dumb for german
engineering.
>
> Have you considered going deeper on your well and finding two
> aquafers, one on top of the other? With this system you would pump
> from the bottom and return on the top. This is done quite extensively
> in Virginia. But with limestone you must have a deep well.
Not for my system but we have discussed it at work for other clients. My
supply well is 340 feet deep and the discharge well is 160 feet deep. The
limestone is so tight I had 50 feet of drawdown when the wells were first
finished. I acid treated the wells and got it down to 5 feet. I suppose I
could do another super acid treatment and improve the well capacity enough
to use it in a double acquifer fashion. trouble is there is only one
acquifer, unless you count the torturous pathway through the rocks as some
degree of separation. It may well be sufficiently separated that way to
allow for significant heat recovery in whatever percentage of the water
that gets double pumped.



>
> BTW, capacity lose in your unit will probably happen soon due to scale
> build up.
> Bacteria is happening due to oxygenization of the water, cant get away
> from it. You can use an ozone generator made for water but its not
> cheap to purchase.

Thanks again - this ozone tip helps me a lot. Do you know what sort of on-
going maintenance I should be doing to prevent or limit or fix scaling? I
have a tee end that I can use to add chemicals to the flow. Have tees at
the main well line in the house and upstream of each heat pump. When the
PRV's are removed I will replace them with tees so I can add something
downstream of each heat pump as well.

>
> Yes, eventually your well will dry up due to plugging of the system
> with all this bacteria building up.
>
> I would suggest two things. First, you mention that you cant put a
> loop in due to shifting of the banks. But your home is on this
> property, aren't you afraid of it slidding into the river? I'm sure
> you can put your horizontal loop somewhere. Loop material is tougher
> than you think, what about your water lines undergroud etc.
>
> Go vertical, your well is vertical, It will cost a lot of money for 8
> tons but, heck, no offence, your an engineer...

The house in the city on one of the nice old neighbourhood streets. My wife
grew up a few blocks away. The house is 300 feet from the riverbank and the
danger area for sliding is only about 100 to 150 feet from the river. The
house water is city system and the sewer and electrical all are buried from
the front of house away from the riverbank. The front yard is only 75 x 95
feet and has over a dozen giant old oak trees. There is no way to snake the
connections for a vertical system without destroying most of the tree
roots. Around here we love our old oaks. Besides much of the yard is
driveway and being cleared of snow all winter the frost gets about 8 feet
deep. You can't make all the vertical loop connections that far below
ground and it makes no sense to me to bring heat up from 50 feet below
ground and then route it through the frost zone to the house.

The backyard is on the riverbank and to snake a few thousand feet of
horizontal loop or vertical loop pipes would take the system too close to
the river and into the slip zone. The banks here are clay which moves very
slightly, just enough to tear up piping. All the neighbors have lawn
irrigation from the river and the ones which are buried are constantly
leaking from breaks due to small movements. They only break near the river
so some guys have switched to above ground pipes for the first 150 feet.

Closed loops would have to circulate some form of anti-freeze and if that
leaked it would kill all the nice oaks in the backyard not to mention a
fine for a chemical spill.


>
> Lastly, if your not in a very populated area put the darn thing in the
> river. First try to explain to the jerks who are incharge that you are
> NOT discharging into the river anything that didn't come out of it.
> Tell them you will actually help it by oxygenating it and you will
> have the water filtered, thus its going back CLEANER than what you
> took out! If they say no, wait until there is a shift in power and do
> it underground and thumb your nose at them. Its obvious their idiots
> so you play the "I didn't know' argument if something develops. Of
> course, you best check out what the penalties are, in Canada you may
> have to be castrated for such an offence~

Our feds have a relatively new law where you can't discharge nothing no-how
and if you do they can fine you $350,000 for a residence first offence.
It's more for commercial guys. I don't think they have tried it yet but I
don't want to be the first. I have to deal with them for all of my design
projects and it is a huge hassle every time.

I did actually give a lot of thought to using river water; it may even cost
a bit less than loops. Problem is the river is held up about 10 feet in the
summer by a bunch of stop logs way downstream of the city. They remove
these stop logs in the fall so the river will not be restricted in the
spring floods. When they take out the logs I have about 50 feet of mud
exposed to the edge of the ice. A river pipe system would have to be buried
about 8 ft below this mud to prevent freezing. That is not too bad as my
buddy has a horizontal directional drill rig; he did my well connections.
Trouble is some sort of intake structure would be required that would stand
up to ice floes in the spring. God help me if some drunk motor boater hits
it in the summer when it is more than 50 feet from shore. My boat ramp gets
silted full every spring when the river is high for a few weeks and I think
an intake manhole or whatever could turn into a solid mud mess in no time.
Then there is the issue of the winter low flow channel moving from year to
year - it could end up 400 feet from my side of the bank some years. I'd
end up with a system that plugged with mud all the time, got wrecked by the
ice every spring and then I'd get sued every time some jerk killed himself
on the intake structure. I'm better off fixing my wells.



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