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Posted by tman on May 18, 2008, 8:17 pm
Hi, my house currently has a DHW coil sitting in a relatively OK oil
boiler (Burnham RSA 110). I put a Hobbs meter on the boiler, and find
that the thing is blowing somewhere around almost 3/4 gal of oil up the
chimney in standby losses per day -- that is just the standby usage with
no DHW or heating load, just to sit there. That is with the Aquastat
set to 125 for the low setpoint, which is about as cool as I want to get
it since I like my water to the washer, dishwasher, etc at least that hot.
So I am thinking about putting in a 50 gal high-efficiency electric hot
water heater to augment it, so that I can turn the boiler off when the
domestic heat is not needed, e.g. over the summer. I understand others
have done this, and have done quite alright saving money with a manual
switch-over, so that their DHW is electric during the warm months and
the oil boiler is "off" during the summer months.
However, being a bit of an engineer, I want to complicate this setup --
can anyone give me advice or gotchas on my plans?
- Electric HW heater is on full-time.
- DHW comes from either electric, or boiler, and is switched by a zone
valve, e.g. like a Taco 3-way.
- A second Aquastat / temp switch installed on the boiler flips the zone
valve to draw hot water from the boiler whenever the boiler temp is over
a certain setpoint, say 120F.
- A timer is rigged into the boiler Aquastat, so that the boiler is
normally off (full cold), but goes on to the lower setpoint (~130F) when
the timer is on -- this would be for anticipated high hot-water demand
days / times, I am thinking 2x / week when a lot of laundry is done.
The boiler is also on to the higher setpoint (~180F) whenever there is a
call for domestic heating, (of course).
My aim is to utilize the lower fuel costs of the oil boiler when the
thing is hot anyways due to a domestic heat call, or at certain limited
times of the week when it switches on in order to supply a heavy
hot-water demand (and economize the fuel cost). The aim is to keep the
boiler cool, and supply hot water from the electric tank, at all other
times.
Kind of different, does anyone see any gotchas?
And two more questions along this thread, if anyone has any advice.
- Where can I get an idea of anticpated future electric costs -- I am in
CT, and pay $0.16 / KWH which is kind of high -- but the price has not
escalated to the rate that oil, gasoline, etc. have in the last 4-6 months.
- Where can I get some info on the standby heat loss from an electic hot
water heater -- I don't see much on the manuf websites.
Thanks much for any advice!!!
T
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Posted by hallerb@aol.com on May 18, 2008, 9:02 pm
> Hi, my house currently has a DHW coil sitting in a relatively OK oil
> boiler (Burnham RSA 110). =EF=BF=BDI put a Hobbs meter on the boiler, and =
find
> that the thing is blowing somewhere around almost 3/4 gal of oil up the
> chimney in standby losses per day -- that is just the standby usage with
> no DHW or heating load, just to sit there. =EF=BF=BDThat is with the Aquas=
tat
> set to 125 for the low setpoint, which is about as cool as I want to get
> it since I like my water to the washer, dishwasher, etc at least that hot.=
>
> So I am thinking about putting in a 50 gal high-efficiency electric hot
> water heater to augment it, so that I can turn the boiler off when the
> domestic heat is not needed, e.g. over the summer. =EF=BF=BDI understand o=
thers
> have done this, and have done quite alright saving money with a manual
> switch-over, so that their DHW is electric during the warm months and
> the oil boiler is "off" during the summer months.
>
> However, being a bit of an engineer, I want to complicate this setup --
> can anyone give me advice or gotchas on my plans?
>
> - Electric HW heater is on full-time.
> - DHW comes from either electric, or boiler, and is switched by a zone
> valve, e.g. like a Taco 3-way.
> - A second Aquastat / temp switch installed on the boiler flips the zone
> valve to draw hot water from the boiler whenever the boiler temp is over
> a certain setpoint, say 120F.
> - A timer is rigged into the boiler Aquastat, so that the boiler is
> normally off (full cold), but goes on to the lower setpoint (~130F) when
> the timer is on -- this would be for anticipated high hot-water demand
> days / times, I am thinking 2x / week when a lot of laundry is done.
> The boiler is also on to the higher setpoint (~180F) whenever there is a
> call for domestic heating, (of course).
>
> My aim is to utilize the lower fuel costs of the oil boiler when the
> thing is hot anyways due to a domestic heat call, or at certain limited
> times of the week when it switches on in order to supply a heavy
> hot-water demand (and economize the fuel cost). =EF=BF=BDThe aim is to kee=
p the
> boiler cool, and supply hot water from the electric tank, at all other
> times.
>
> Kind of different, does anyone see any gotchas?
>
> And two more questions along this thread, if anyone has any advice.
> - Where can I get an idea of anticpated future electric costs -- I am in
> CT, and pay $0.16 / KWH which is kind of high -- but the price has not
> escalated to the rate that oil, gasoline, etc. have in the last 4-6 months=
.
> - Where can I get some info on the standby heat loss from an electic hot
> water heater -- I don't see much on the manuf websites.
>
> Thanks much for any advice!!!
> T
http://www.aceee.org/consumerguide/waterheating.htm
is a water heater comparision site, chock full of info.
the cost of oil hasnt been updated but electric still appears cheaper.
might well be cheaper than using the boiler oil at any time.
one needs to coinsider complexity and reliability,,,,,,,,,
while your idea may save a few bucks one malfunction where you home
doesnt heat might cost you far more:(
have you checked the efficency of new boilers? and upgrading
insulation?
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Posted by RBM on May 18, 2008, 9:03 pm
> Hi, my house currently has a DHW coil sitting in a relatively OK oil
> boiler (Burnham RSA 110). I put a Hobbs meter on the boiler, and find
> that the thing is blowing somewhere around almost 3/4 gal of oil up the
> chimney in standby losses per day -- that is just the standby usage with
> no DHW or heating load, just to sit there. That is with the Aquastat set
> to 125 for the low setpoint, which is about as cool as I want to get it
> since I like my water to the washer, dishwasher, etc at least that hot.
>
> So I am thinking about putting in a 50 gal high-efficiency electric hot
> water heater to augment it, so that I can turn the boiler off when the
> domestic heat is not needed, e.g. over the summer. I understand others
> have done this, and have done quite alright saving money with a manual
> switch-over, so that their DHW is electric during the warm months and the
> oil boiler is "off" during the summer months.
>
> However, being a bit of an engineer, I want to complicate this setup --
> can anyone give me advice or gotchas on my plans?
>
> - Electric HW heater is on full-time.
> - DHW comes from either electric, or boiler, and is switched by a zone
> valve, e.g. like a Taco 3-way.
> - A second Aquastat / temp switch installed on the boiler flips the zone
> valve to draw hot water from the boiler whenever the boiler temp is over a
> certain setpoint, say 120F.
> - A timer is rigged into the boiler Aquastat, so that the boiler is
> normally off (full cold), but goes on to the lower setpoint (~130F) when
> the timer is on -- this would be for anticipated high hot-water demand
> days / times, I am thinking 2x / week when a lot of laundry is done. The
> boiler is also on to the higher setpoint (~180F) whenever there is a call
> for domestic heating, (of course).
>
> My aim is to utilize the lower fuel costs of the oil boiler when the thing
> is hot anyways due to a domestic heat call, or at certain limited times of
> the week when it switches on in order to supply a heavy hot-water demand
> (and economize the fuel cost). The aim is to keep the boiler cool, and
> supply hot water from the electric tank, at all other times.
>
> Kind of different, does anyone see any gotchas?
>
> And two more questions along this thread, if anyone has any advice.
> - Where can I get an idea of anticpated future electric costs -- I am in
> CT, and pay $0.16 / KWH which is kind of high -- but the price has not
> escalated to the rate that oil, gasoline, etc. have in the last 4-6
> months.
> - Where can I get some info on the standby heat loss from an electic hot
> water heater -- I don't see much on the manuf websites.
>
> Thanks much for any advice!!!
> T
My opinion is to install a manual bypass system that allows you to use
either system independently, don't create a control and wiring nightmare,
use the oil burner during the winter and the electric during the summer and
drain it when not in use
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Posted by John Grabowski on May 18, 2008, 9:47 pm
> Hi, my house currently has a DHW coil sitting in a relatively OK oil
> boiler (Burnham RSA 110). I put a Hobbs meter on the boiler, and find
> that the thing is blowing somewhere around almost 3/4 gal of oil up the
> chimney in standby losses per day -- that is just the standby usage with
> no DHW or heating load, just to sit there. That is with the Aquastat set
> to 125 for the low setpoint, which is about as cool as I want to get it
> since I like my water to the washer, dishwasher, etc at least that hot.
>
> So I am thinking about putting in a 50 gal high-efficiency electric hot
> water heater to augment it, so that I can turn the boiler off when the
> domestic heat is not needed, e.g. over the summer. I understand others
> have done this, and have done quite alright saving money with a manual
> switch-over, so that their DHW is electric during the warm months and the
> oil boiler is "off" during the summer months.
>
> However, being a bit of an engineer, I want to complicate this setup --
> can anyone give me advice or gotchas on my plans?
>
> - Electric HW heater is on full-time.
> - DHW comes from either electric, or boiler, and is switched by a zone
> valve, e.g. like a Taco 3-way.
> - A second Aquastat / temp switch installed on the boiler flips the zone
> valve to draw hot water from the boiler whenever the boiler temp is over a
> certain setpoint, say 120F.
> - A timer is rigged into the boiler Aquastat, so that the boiler is
> normally off (full cold), but goes on to the lower setpoint (~130F) when
> the timer is on -- this would be for anticipated high hot-water demand
> days / times, I am thinking 2x / week when a lot of laundry is done. The
> boiler is also on to the higher setpoint (~180F) whenever there is a call
> for domestic heating, (of course).
>
> My aim is to utilize the lower fuel costs of the oil boiler when the thing
> is hot anyways due to a domestic heat call, or at certain limited times of
> the week when it switches on in order to supply a heavy hot-water demand
> (and economize the fuel cost). The aim is to keep the boiler cool, and
> supply hot water from the electric tank, at all other times.
>
> Kind of different, does anyone see any gotchas?
>
> And two more questions along this thread, if anyone has any advice.
> - Where can I get an idea of anticpated future electric costs -- I am in
> CT, and pay $0.16 / KWH which is kind of high -- but the price has not
> escalated to the rate that oil, gasoline, etc. have in the last 4-6
> months.
> - Where can I get some info on the standby heat loss from an electic hot
> water heater -- I don't see much on the manuf websites.
>
> Thanks much for any advice!!!
> T
KISS. Keep it simple sexy. As others suggested you don't want a maintenance
nightmare. I just spent 3 full days wiring up a heat and hot water system
with 14 pumps and 4 controllers and a few relays for a three floor
mcmansion. I pity the poor tech person who will be servicing the system in
a few years.
I am in NJ and my electric rate is at its peak during the day in the summer
so I would not want more electricity consumption during those peak months.
Maybe you have a fixed rate year round.
Is it possible to convert to an on demand high efficiency boiler with a
storage tank to supply your domestic hot water?
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Posted by Pete C. on May 18, 2008, 9:54 pm
tman wrote:
>
> Hi, my house currently has a DHW coil sitting in a relatively OK oil
> boiler (Burnham RSA 110). I put a Hobbs meter on the boiler, and find
> that the thing is blowing somewhere around almost 3/4 gal of oil up the
> chimney in standby losses per day -- that is just the standby usage with
> no DHW or heating load, just to sit there. That is with the Aquastat
> set to 125 for the low setpoint, which is about as cool as I want to get
> it since I like my water to the washer, dishwasher, etc at least that hot.
>
> So I am thinking about putting in a 50 gal high-efficiency electric hot
> water heater to augment it, so that I can turn the boiler off when the
> domestic heat is not needed, e.g. over the summer. I understand others
> have done this, and have done quite alright saving money with a manual
> switch-over, so that their DHW is electric during the warm months and
> the oil boiler is "off" during the summer months.
>
> However, being a bit of an engineer, I want to complicate this setup --
> can anyone give me advice or gotchas on my plans?
>
> - Electric HW heater is on full-time.
> - DHW comes from either electric, or boiler, and is switched by a zone
> valve, e.g. like a Taco 3-way.
> - A second Aquastat / temp switch installed on the boiler flips the zone
> valve to draw hot water from the boiler whenever the boiler temp is over
> a certain setpoint, say 120F.
> - A timer is rigged into the boiler Aquastat, so that the boiler is
> normally off (full cold), but goes on to the lower setpoint (~130F) when
> the timer is on -- this would be for anticipated high hot-water demand
> days / times, I am thinking 2x / week when a lot of laundry is done.
> The boiler is also on to the higher setpoint (~180F) whenever there is a
> call for domestic heating, (of course).
>
> My aim is to utilize the lower fuel costs of the oil boiler when the
> thing is hot anyways due to a domestic heat call, or at certain limited
> times of the week when it switches on in order to supply a heavy
> hot-water demand (and economize the fuel cost). The aim is to keep the
> boiler cool, and supply hot water from the electric tank, at all other
> times.
>
> Kind of different, does anyone see any gotchas?
>
> And two more questions along this thread, if anyone has any advice.
> - Where can I get an idea of anticpated future electric costs -- I am in
> CT, and pay $0.16 / KWH which is kind of high -- but the price has not
> escalated to the rate that oil, gasoline, etc. have in the last 4-6 months.
> - Where can I get some info on the standby heat loss from an electic hot
> water heater -- I don't see much on the manuf websites.
>
> Thanks much for any advice!!!
> T
If you put the electric DHW downstream of the boiler's tankless coil and
have it's thermostat set slightly below the aquastat on the boiler, when
the boiler is running during the heating season the electric HW will not
operate much at all and will act as an insulated accumulator tank. When
the boiler is shut off in the summer the electric heater will operate
since the incoming water will be cold. No fancy controls or valves
needed.
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