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Posted by MRnice on November 29, 2005, 9:35 am
My Dunham/Bushe residential boiler is a hot water boiler with a forced
hot air central heating system. It has been running at a high pressure
(30 lbs.) and this is causing the pressure relief valve to release
water. I drained the expansion tank (which was full) by shutting the
feed and opening the drain valve. It is an old system with no
compressed air in the tank, which I believe does not have a bladder in
the tank. It does have a shut off valve below the inlet to the tank
and a drain valve with a hosecock connection on the opposite side. The
inlet and drain are both on the bottom of the tank. After I drain it
the system functions fine for a day until the pressure builds up and
the tank is full again. I think I am bleeding it right, or am I? The
pressure relief valve does go off due to the high pressure, but does
seem to seat well after the pressure goes down. After reading some of
the postings on the board, I also thought that the temperature setting
on the aquastat may be too high. It is currently set at 160 as the
high and 130 as the low with a 10 degree differential. What would the
correct temperature setting be?
I would appreciate any assistance. Thank you, MRnice
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Posted by Speedy Jim on November 29, 2005, 9:43 am
MRnice wrote:
> My Dunham/Bushe residential boiler is a hot water boiler with a forced
> hot air central heating system. It has been running at a high pressure
> (30 lbs.) and this is causing the pressure relief valve to release
> water. I drained the expansion tank (which was full) by shutting the
> feed and opening the drain valve. It is an old system with no
> compressed air in the tank, which I believe does not have a bladder in
> the tank. It does have a shut off valve below the inlet to the tank
> and a drain valve with a hosecock connection on the opposite side. The
> inlet and drain are both on the bottom of the tank. After I drain it
> the system functions fine for a day until the pressure builds up and
> the tank is full again. I think I am bleeding it right, or am I? The
> pressure relief valve does go off due to the high pressure, but does
> seem to seat well after the pressure goes down. After reading some of
> the postings on the board, I also thought that the temperature setting
> on the aquastat may be too high. It is currently set at 160 as the
> high and 130 as the low with a 10 degree differential. What would the
> correct temperature setting be?
>
> I would appreciate any assistance. Thank you, MRnice
>
I think you have a good understanding of the system and
how that ancient exp tank works. Should work with those
temp settings OK.
It's possible that an automatic fill valve from the
incoming water supply is leaking and refilling the system,
causing the high pressure. Find a shutoff valve and close
it to find out.
Jim
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Posted by MRnice on November 29, 2005, 11:18 am
I am emptying the tank again to make sure it is totally empty. I think
air will enter through the drain valve into the tank, which should be a
good thing if I understand how this tank works. I will look for a
valve on the autofeeder, I know on a steam system it regularly fills
which you can see in a guage glass. I am not as familure with Hot
water systems. I guess too much water would push up against the
pressure relief valve causing the 30+ lb. reading on the guage too. Of
course, I know this is a more difficult fix. If I wanted to run the
boiler without the feedwater regulator for a while, how often would I
add water to the boiler? How would I know when it needs it? Thank you
for your suggestion, it seems like the only other reason for high
pressure. The stack is clean, relief valve seems to work only at
preset 30lb. and the temp. is not too high. Do these boilers require
any cleaning , chamber, etc.? I have changed the oil filter, replaced
a bad ignitor last season (my first season in home), and cleaned the
flame scanner eye as well as changed the nozzle. Could lack of prior
maintenance have caused sediment buildup to produce a high stack
pressure causing a problem? Thank you for your advice, Ron
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Posted by Speedy Jim on November 29, 2005, 12:20 pm
MRnice wrote:
> I am emptying the tank again to make sure it is totally empty. I think
> air will enter through the drain valve into the tank, which should be a
> good thing if I understand how this tank works. I will look for a
> valve on the autofeeder, I know on a steam system it regularly fills
> which you can see in a guage glass. I am not as familure with Hot
> water systems. I guess too much water would push up against the
> pressure relief valve causing the 30+ lb. reading on the guage too. Of
> course, I know this is a more difficult fix. If I wanted to run the
> boiler without the feedwater regulator for a while, how often would I
> add water to the boiler? How would I know when it needs it? Thank you
> for your suggestion, it seems like the only other reason for high
> pressure. The stack is clean, relief valve seems to work only at
> preset 30lb. and the temp. is not too high. Do these boilers require
> any cleaning , chamber, etc.? I have changed the oil filter, replaced
> a bad ignitor last season (my first season in home), and cleaned the
> flame scanner eye as well as changed the nozzle. Could lack of prior
> maintenance have caused sediment buildup to produce a high stack
> pressure causing a problem? Thank you for your advice, Ron
>
Unless there is a leak, that boiler shouldn't need
feed water except in rare cases.
Oil-fired does need annual maintenance for cleaning
and combustion air setting, etc. But that's not
part of this problem.
That has to be a cast iron boiler, so there are no tubes.
Get the pressure under control and see if there is any
evidence of leaks.
Jim
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Posted by MRnice on November 29, 2005, 11:22 am
I also wonder if one of the tubes could be leaking inside the boiler.
There is alot of water on the floor, but I thought it must be from the
Pressure relief valve blowing down.
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> hot air central heating system. It has been running at a high pressure
> (30 lbs.) and this is causing the pressure relief valve to release
> water. I drained the expansion tank (which was full) by shutting the
> feed and opening the drain valve. It is an old system with no
> compressed air in the tank, which I believe does not have a bladder in
> the tank. It does have a shut off valve below the inlet to the tank
> and a drain valve with a hosecock connection on the opposite side. The
> inlet and drain are both on the bottom of the tank. After I drain it
> the system functions fine for a day until the pressure builds up and
> the tank is full again. I think I am bleeding it right, or am I? The
> pressure relief valve does go off due to the high pressure, but does
> seem to seat well after the pressure goes down. After reading some of
> the postings on the board, I also thought that the temperature setting
> on the aquastat may be too high. It is currently set at 160 as the
> high and 130 as the low with a 10 degree differential. What would the
> correct temperature setting be?
>
> I would appreciate any assistance. Thank you, MRnice
>