no heat in two radiators

salio

We have a hydronic converted gravity heating system, gas fired boiler. So forced circulation now, and just one zone for the entire house. I forget an awful lot of things, but for some reason I remember it was "564 sq. ft radiation" when we had the new boiler installed and the system converted about 23 years ago.

Something new just this year is that two second floor radiators are not heating at all, while all the others are fully heating. Some of them had a little air, but not much. One of the radiators not heating is in the second floor bathroom. The radiator in the bathroom directly below is plenty hot. I guess it's a 'two pipe' system because there's a supply and return pipe running up the wall inside, but the pipes going up to the second floor and the entire radiator are stone cold. There is an inlet valve at the supply side of each radiator in the house.

I opened the bleeder valve on the upstairs radiator, heard air escaping for less than a minute, then it stopped but I never got water. The next day I removed the bleeder valve, got a brief puff of air, then nothing - turned the thermostat up to make sure the circulation pump was running (it's wired to come on with the call for heat), still nothing. It's a newer valve that is fully functional. I loosened the packing nut without pulling out the valve to see if water or air would release, but got nothing.

The other radiator that's not heating is in an adjacent second floor bedroom though it's supply and return lines are on a different loop and within the wall cavity. But there's also a radiator in our DR which is directly below that one (I think), and that radiator if fully heating as well. I took the same steps with it as far as bleeding air, and got the same results. I can't imagine anything being frozen because we haven't even dropped below 36 degrees yet, and though I have to bleed the radiators a couple times a year, we've never had any part of the system freeze.

It's got me baffled!

Ironman

What’s the pressure on the boiler gauge? It sounds like the system pressure is too low and that maybe your fill valve isn’t working.

You should have a minimum of 12-15 psi when the system is cold.

JUGHNE

What shows on your pressure gauge? You need about 15 PSI when system is cold/cool. This pushes the water up to the 2nd floor. Then you would need to bleed air out.
A little air with no water up there tells that the water is not high enough in the system.
Do you know how to add water to the system?
Pictures would help us.

Jamie Hall

These ^^^. To which I will add: don't be misled if there are other second floor radiators which do work. That simply means that if the pressure is low nothing has happened to break the siphon which they represent. Like an air leak. Or bleeding them...

EBEBRATT-Ed

@salio

All of the above +

Could be a bad water feeder or a bad expansion tank

Probably a fairly easy fix

salio

You guys are right - boiler pressure is at zero. Thankfully most of the house is warm. It's one zone so one circulator, a B&G NRF-22. Is my circulator bad? How do I actually check it?

JUGHNE

Probably not.

You need to add water to boiler (when cool/cold) to bring pressure up to that 15 PSI.

Post pictures of water feeder and it's connections.

EBEBRATT-Ed

Since you were getting heat on the lower floor the circulator is probably ok

Ironman

It’s not the circulator that pressurizes the system; the fill valve (aka a pressure reducing valve) is what does it. It’s connected to a 1/2” cold water line feeding the boiler.

salio

Problem solved and you were all right. Boiler pressure was at zero and thankfully my brother was here visiting who went immediately to the fill valve as you said. The pressure is up, the two cold radiators are bled, filled and hot. Thanks guys, heat is nice!