Help with gas/steam/hydronic system

nestor87

Hi -- I have a gas-fired steam boiler that feeds cast iron radiators throughout my home. In addition, I have a system that pump hot water from the boiler to an air handler in the attic to provide forced air heat throughout the home also. But in the two years I have lived here, I have never been able to get the hydronic system to actually warm the air coming out of the air handler. When I run it, I can feel water flowing through the plastic tubing, and in the boiler room the plastic tubing feels warm. But at the air handler, it stays cold no matter how long I run it. Could this be a problem with with air in the system? Or something more involved? It's tough to take pictures in the boiler room, but here's an attempt:

Ironman

Is there a heat exchanger between the boiler and the AHU?

nestor87

yes, there is. Hard to see it in the picture, but it's below the expansion tank.

Intplm.

When the system is running, and calling for heat. Can you keep your hand wrapped around the metal piping on the heating zone. You should not be able too as it comes up to temp. It should be too hot.
If you can hold on to it without the heat making you let go, the system is probably air bound and needs to be purged.

nestor87

Ah - correction: after a good 20-30 minutes running constantly, there is finally some warm water coming through the tubing at the air handler. Is this a normal amount of time? Seems like there is something off here.

nestor87

Thank you! How would I purge a system like this?

Intplm.

You have to replace the air with water.
If there is a purge valve at the air handler that's a good place to start.

The two valves with yellow handles with boiler drains just above. those two set ups are there to purge the two pictured zones.
Can you post more pictures? further away and at different angles?
If not that's fine if you only have the two zones. ?

nestor87

There is no valve at the air handler, just the one tube going in and the one tube coming out.

I am a little confused about the two zones, because the hydronic system is on a single thermostat, and the steam radiator system is on a second thermostat. So I was under the impression that I had two total zones, not two hydronic zones. here are some additional pictures. Thank you very much for your help!

Intplm.

Ok, better pics but we need one more. One more or two, is needed that of the boiler. So far I can't be sure if you have a steam boiler, hot water boiler or a conversion. Please post a few pics of the boiler.
The pressure gage and other components.

nestor87

It's a steam boiler -- one-pipe steam radiators throughout the house.

Jamie Hall

I'd be reasonably sure you have air up there in the air handler -- and there should be a bleed valve up there. just purging may not do the job. The next question I'll ask is what is the static system pressure on the air handler/heat exchanger loop? And the next question is what keeps the boiler warm enough to provide heat to the heat exchanger, and what pumps water through the boiler side of the heat exchanger?

tim smith

Is there a hose bib up at air handler and you definitely get water out of it at air handler? If you do, then may either need purging or you have a bad pump or relay that turns pump on. Is there a pressure gauge any where on the heating loop for the air handler. That will also tell us if you have enough pressure to get up to your air handler depending on how many stories it is to air handler. Ideally close amount of feet from gauge to air handler in vertical distance.

kcopp

This is a steam boiler. Looks like a brazed plate HX. Would not be surprised if the BP HX is plugged w/ mud.