No heat, sudden high pressure!

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Old 01-03-12, 10:00 AM
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No heat, sudden high pressure!

Hi everyone, I have a hot water radiator system in a 100 year old 2 1/2 story house. I woke up this morning to no heat, and when I checked the furnace the water temps are all the way down, and the pressure is at 30 PSI. We normally have it more around 20 to get up to the third floor. Here's a link to pics and a diagram that i made for another thread about other issues.

https://www.dropbox.com/gallery/6507...ystem?h=3a1c27
 
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Old 01-03-12, 03:09 PM
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I'm unable to think of a common cause for the boiler going out and the pressure being high. So, my theory is that these are two, separate events.

One thing that can cause the pressure to be too high, even with the boiler cooled down - the pressure regulating valve leaking past its seat, overfilling the boiler with water. This may have been going on for a while before the boiler went out. Has the relief valve been lifting and spewing water onto the floor?

There are many possible reasons for the heat to go out, for example: pilot blown out or any number of failures in the boiler control system. If you have a standing pilot, is it burning? If it is, then it's time troubleshoot with a multimeter to find out where the control voltage is being lost. If you don't have the experience to do this, you'll likely have to call for help.
 
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Old 01-03-12, 04:22 PM
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More:

You said the increase in pressure was "sudden." When was the last time you had checked the pressure before last night?

I looked at your "old" photos again. Whenever those pix were taken, there was a damp spot beneath the discharge from the relief valve. That is more support for my theory that the pressure problem has been going on for some time, and unobserved.

See the blue-handled valve, leading from your city water supply to the gold-colored pressure-reducing valve? Shut that blue valve temporarily, drain water from the boiler to your chosen cold pressure, monitor the boiler pressure for a few days, and report back. We'll then advise you further.

You said that your normal cold pressure is 20 psi, because you have a 2-1/2 storey house. What is the half storey and how high is it? If you are counting the basement, 15 psi (cold) is OK.

That business with the heating going off is, I believe, a separate problem.
 
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Old 01-03-12, 05:40 PM
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A 1/2 story is another floor, but the living space is about 1/2 of the floor below it. Typically a finished attic space is a 1/2 floor. This would be considered a 3rd floor for the context of boiler pressure and a 1/2 floor for the context of property tax.

As gilmorrie stated, this could be a problem with water leaking past your pressure regulator. However, the most common problem of pressure rise like this is a bad expansion tank. You should check the pressure in your expansion tank. To do so, you will need to drain water out of your system until the pressure is zero. Typically the tanks are hung so the schrader valve is on the bottom. When it is like that, you can tell when the bladder goes bad because water will come out of the valve when you check the pressure.
 
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