Hot water heating pressure problem

jharuni

I have a gas hot water home heating system with a boiler in the basement and rads on three floors -- ground, second, and attic. Near the boiler is a pressure regulator valve, a pressure gauge, and a pressure relief valve.

With the regulator at its factory setting of 15psi, the attic radiators do not bleed out -- not enough pressure. According to the regulator documentation, the factory setting of 15 is "sufficient for a 3 story building". Also in that document is a formula converting feet of water to required PSI --- and if I measure very generously I get 31 feet or 16.4PSI.

Slowly raising the pressure to 18 and 20, I got a little more air out of the attic rads but no water. I had to increase the pressure to 22 (according to the boiler gauge) before they filled up. Now I have other problems: the PRV drips. And (less important) with the regulator screwed down to 22psi there is not enough thread showing to attach the fast-fill valve. Not a big deal but seems like a stupid design.

Anyway, my two problems are:
1. Why do I need 22 pounds to fill the attic, maxing at 31 feet above the basement floor ? Any theories ?
2. Is it normal for a 30lb PRV to drip at 22 ? What can I do ? I suppose it is possible that the dripping is not because of the higher pressure but simply because I was playing with it too much during my experimentation. Would that be normal ? The entire system is about 8 years old, except the pipes and rads which are much older.

How should I approach this ? I'm tired of running back and forth between the basement and attic, 4 or 5 times, every time the rads need bleeding, and I obviously don't want a non-stop hot-water drip in my basement.

Al Letellier

altitude problem

Here's some possibilities: The gauge isn't accurate and the gauge may not be right. In a case like this, you need whatever pressure you need to get the water to the highest radiator. As to the safety dripping: set at 22 Psi with a 30# safety, you may be getting expansion that is setting off the safety or the xtank my not be set correctly.
If the boiler specs say so, you can install a 40# pressure relief and add the pressure you need. This should solve your problem. If the gauge is accurate, and the safety is dripping, replace it. You may have torn the gasket on the seat and it may never reseat, or some debris is blocking it from seating properly. Have a pro check it out for you.

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Brad White_5

Filling and Venting...

Generally you want at least 4-5 psig at the top of a system to assure no vacuum pull-down when you start the pump. That is a hold-over from the "pumping into the boiler days". But it is still good practice.

First thing I would do is make sure that you are "pumping away" from the expansion tank. This will add the pump pressure to the system static pressure and initiate flow. (Pumping TO the expansion tank will draw a negative suction pressure into the system. This may draw in air through top automatic vents.)

Secondly, if 31 feet is your system height, divide by 2.31 to obtain PSI. Then add 4 or 5 PSI on top of that. I get 13.42 PSI net, and call it 18 psi to top off the system. 22 PSI should be plenty IF you are pumping away from the expansion tank. And IF your measurement of height or gauge is accurate. That should answer your first question.

The second question, the relief valve- It ought not weep until it gets to 29 psi or so. They are fairly precise for spring loaded devices. If it is weeping, chances are there is some debris on the seat. Open it manually to flush it out and see if it re-sets. Funny thing is, it is often the very act of opening the valve to "test" it that places the bit of grit there in the first place!

I am sure you do not have to be told, but I see it now and again. A homeowner "solves" the dripping relief valve problem by capping the offending orifice.

(Anyone who does that IS an offending orifice IMHO, and makes a potential bomb that would level Fallujah. Wait, I have an idea...)

System age ought not be a factor in my opinion.