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Pressure in a hydronic heating system Marilyn & Bob 02-07-2007
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Posted by Marilyn & Bob on February 7, 2007, 12:20 am


We have a four story plus cellar 1840's 2 family house with a hydronic
heating system with large radiators that was probably installed in the
1920's. The gas boiler is about 20 years old. The system has both a
conventional expansion tank (that has not been emptied in years) and a
Filltrol diaphragm expansion tank in series.

Every place I looked on the web (including the Filltrol site) says that the
system pressure should be set at 12 psi when cold and should be 20 psi when
hot and circulating. That is exactly where it is, but the radiators on the
4th floor seem to have some air left in them. When bled, water does not
come out of the valve and the top of the radiators are not very hot (the
bottom halves are).

Should the pressure be higher in a 4 story house that in a shorter one? And
if so what should it be? And how do I adjust it? The Filltrol manual does
not give instructions other than to say that it is adjusted via the intake
air valve and should be adjusted when the tank is empty.

So (if I really do need to increase the pressure) do I add air (and how
much) or remove air from the Filltrol expansion tank. And do I have to
completely drain the system to do it? Or just let out a few gallons of
water? Or not concern myself with letting any water out.

A link to a good website will suffice. As I said, my Google search was
unproductive.
--
Peace,
BobJ



Posted by SuperPoo on February 7, 2007, 1:30 am



> We have a four story plus cellar 1840's 2 family house with a hydronic
> heating system with large radiators that was probably installed in the
> 1920's. The gas boiler is about 20 years old. The system has both a
> conventional expansion tank (that has not been emptied in years) and a
> Filltrol diaphragm expansion tank in series.
>
> Every place I looked on the web (including the Filltrol site) says that
> the system pressure should be set at 12 psi when cold and should be 20 psi
> when hot and circulating. That is exactly where it is, but the radiators
> on the 4th floor seem to have some air left in them. When bled, water
> does not come out of the valve and the top of the radiators are not very
> hot (the bottom halves are).
>
> Should the pressure be higher in a 4 story house that in a shorter one?
> And if so what should it be? And how do I adjust it? The Filltrol manual
> does not give instructions other than to say that it is adjusted via the
> intake air valve and should be adjusted when the tank is empty.
>
> So (if I really do need to increase the pressure) do I add air (and how
> much) or remove air from the Filltrol expansion tank. And do I have to
> completely drain the system to do it? Or just let out a few gallons of
> water? Or not concern myself with letting any water out.
>
> A link to a good website will suffice. As I said, my Google search was
> unproductive.
> --
> Peace,
> BobJ

http://heatinghelp.com/ Tons of info there if you can not find what you need
on the site they have a forum where you can post questions. My feeling is 20
psi should get to the fourth floor. 1 psi will roughly lift water 2.31' so
20 psi should get you 46.2 feet-- there are other varibles that may come
into play too that may shorten that estimate. If you search google using
combos of verticle lift, psi, water, head-- you will find some more of what
you are looking for.

Steve
>
>



Posted by m Ransley on February 7, 2007, 7:39 am


You dont even know if your gauge is accurate, Add water to a COLD boiler
of 70f while bleeding air out of the top floor while boiler is running
till water comes out the radiator. Your issue is not enough Altitude or
Pressure. Dont mess with anything else. Then see how it works and
monitor pressure cold and hot, it may only take a Lb or 2 of water to
get heat to the top. After a few hours bleed radiators again. It may
take a few tries over a few days.


Posted by Marilyn & Bob on February 8, 2007, 12:16 pm



> You dont even know if your gauge is accurate, Add water to a COLD boiler
> of 70f while bleeding air out of the top floor while boiler is running
> till water comes out the radiator. Your issue is not enough Altitude or
> Pressure. Dont mess with anything else. Then see how it works and
> monitor pressure cold and hot, it may only take a Lb or 2 of water to
> get heat to the top. After a few hours bleed radiators again. It may
> take a few tries over a few days.
>

Thanks, I'll try that.
--
Peace,
BobJ



Posted by Marilyn & Bob on February 8, 2007, 12:16 pm



>
>> We have a four story plus cellar 1840's 2 family house with a hydronic
>> heating system with large radiators that was probably installed in the
>> 1920's. The gas boiler is about 20 years old. The system has both a
>> conventional expansion tank (that has not been emptied in years) and a
>> Filltrol diaphragm expansion tank in series.
>>
>> Every place I looked on the web (including the Filltrol site) says that
>> the system pressure should be set at 12 psi when cold and should be 20
>> psi when hot and circulating. That is exactly where it is, but the
>> radiators on the 4th floor seem to have some air left in them. When
>> bled, water does not come out of the valve and the top of the radiators
>> are not very hot (the bottom halves are).
>>
>> Should the pressure be higher in a 4 story house that in a shorter one?
>> And if so what should it be? And how do I adjust it? The Filltrol
>> manual does not give instructions other than to say that it is adjusted
>> via the intake air valve and should be adjusted when the tank is empty.
>>
>> So (if I really do need to increase the pressure) do I add air (and how
>> much) or remove air from the Filltrol expansion tank. And do I have to
>> completely drain the system to do it? Or just let out a few gallons of
>> water? Or not concern myself with letting any water out.
>>
>> A link to a good website will suffice. As I said, my Google search was
>> unproductive.
>> --
>> Peace,
>> BobJ
>
> http://heatinghelp.com/ Tons of info there if you can not find what you
> need on the site they have a forum where you can post questions. My
> feeling is 20 psi should get to the fourth floor. 1 psi will roughly lift
> water 2.31' so 20 psi should get you 46.2 feet-- there are other varibles
> that may come into play too that may shorten that estimate. If you search
> google using combos of verticle lift, psi, water, head-- you will find
> some more of what you are looking for.
>
> Steve
>>

Thank you for the info. I did not see your response before I responded to a
later post reasking the question that you already answered. Since the water
only has to rise about 35 above the circulator pump outlet, I should be
fine.
--
Peace,
BobJ



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