Hi all, hopefully someone can answer my question.

I own a furnace that has a secondary boiler (split system), 1 side boiler + gas/water pipes, and 1 side has the forced air blower and air pipes that run across the house.


ISSUE #1
Pipes are hammering, can it be stopped or be reduced?

ISSUE#2
Boiler gets to its coldest point and restarts as it should but keeps stopping and restarting from time to time until it gets to 160, is that normal?

ISSUE#3
System seem to work properly (17-20 PSI), temp is set up to 130-160, HOWEVER a few days ago it started heating and after it stops one time it restarts with COLD air, someone told me to bleed air out of the system, does it makes sense?


Thanks! :cool:

1 yes it can be stopped

2 yes if the boiler is generating more heat than can be removed by the baseboard/fan coils or what ever you are using to disipate the heat generated by the boiler.

3 yes you can bleed the air out of the system if that is what is needed. Air can also cause water hammer.

Thanks for the answers Hvac.


Did you ever come a cross an issues like this when you didn't have hot air blowing and hammering pipes and releasing air helped? Even on a non combined system? (main water tank + a separate boiler)


When the system is turned off and restarts from scratch when things are cooled down: then the system works, but once the thermostat stops it - it starts again, and the water pressure goes to 0 instead of 15-20 PSI :eek:, the pipes and temp. are hot and the air coming out of the vents is COLD (fan)

Any idea why? Thanks!

You might have a pump problem but that would not explain the drop in pressure. When the water pressure is Zero no water is being pumped to the coil and that is why it is blowing cold air,
One more item it might be the zone valve or solenoid valve that is not opening on the fan coil also.

There are many more reasons that can cause this problem but many are difficult to explain without seeing exactly what your system consists of and how the mainline is run to service domestic hot water and also boiler temp water for heat.

Your system is losing pressure somewhere. I have seen before where the hot water container ends up with a leak in the domestic coil and that can be a problem also.

Hi thanks a lot for the response.

I just solved the water pressure issue, what happened is that a technician closed the main water valve telling me that it doesn't have to be open.

(The pump seem to work, it makes a noise from time to time and I can hear water)

Since he did it when I started the system, water came in (probably cycling water) but once the system shot off by the thermo. And restarted the pressure stayed 0 probably because new fresh water had to come in - now its fine.

Unless I shot off the system and turn it on once its cooled down... then it is blowing warm air until the thermo. Shots it down and so on and so on.

So now the pressure is stable but.. still the system pipes are hot and the air drift is cool :o , what is the reason?



Thanks!

So now the pressure is stable but.. still the system pipes are hot and the air drift is cool , what is the reason? Could it be the air in the system that needs to be purged?

Bleed the coil. There should be a bleeder at every coil in a water to air system. Also FYI usually the water temp for air coil operation is 190 F. Now it does not have to be that hot to work but that temp will allow the human hand to feel warm air instead of luke warm air. The 190F temp is kind of like a industry standard for water to air systems.

BTW I have three hot water coils running off one central boiler in this house. Been working fine for over 25 years.

Thanks for the answer, here are more specific details:

I have a LAARS boiler with 2 pipes that go across the room to the air system, between them I have an expansion tank and a leaking backwash preventer.

On the top part of the expension tank I have an air bleeder.

The temp and PSI are good, the air keeps running cold - UNLESS I turn the whole thing off and restart the system once its temp is low enough for the boiler to start, and then it spreads warm air...

Based on that maybe you can get a clearer picture of the situation?

(Appreciate your help)

Fix this leaking backwash preventer.it should not leak.
Check the pump impeller for condition.
Try and bleed all the air out of the system.

After this I am lost since I am not there to see and diagnosis the problem.

Thanks Hvac! Too bad I can't fly you in :)