Furnace turns on @ 6 hr intervals w/ noise

[patrice]

Okay, this is going to be a very non-technical question ... so please bear with me. We have a hydro-air system, a Peerless Furnace and First Co (air return??). Our house is 1.5 yrs old. Recently, we've had a clunking noise reverberating from the basement which I have found to be in exact 6 hour intervals. What happens is one of the zones (we have 3) calls for heat, the furnace turns on, about 2 minutes later the furnace turns off with a whoosh and then across the room by the air handler there's a clunk. I've had our furnace repair guy here and he's disconnected the wires to the furnace from that zone and the noise doesn't happen. Then he tried disconnecting just from the thermostat and it still happens. He thinks there could be a crossed wire? But it doesn't make sense that something is timing this at exact 6 hour intervals. Any ideas, this is driving us crazy!!!!

[ultratec]

I will take a stab at this one lol. You have a peerless boiler, first company a/h with hot water coil, correct? Not sure where you live and it doesnt matter, just couldnt believe that your still using heat.. If you have programable stats on other zones that may be calling for heat at that 6th hour, its possible that you have a bad zone valve (if you have one circulator) or you have a leaking or defective one way check on that zone causing water to enter that coil and turn on the blower on that zone????????? The fan may come on if the coil gets hot unless your fan control for heat is done by the stat and not water temp to that zone. Is the noise your hearing the duct making noise when the fan comes on?. Just a stab in the dark without being there myself..

[patrice]

Thanks for being so brave to reply to my issue. And you are correct my heat is off, but this is happening whether the thermostats are on heat, off or A/C. We've checked the programs on all the other zones and there's nothing set for that timeframe. The noise is like a pressure release. Once the furnace goes off, you hear like a hissing sound then across the room you hear like a pipe clunk. I will pass along your response to our repairman. If you can think of anything else, I'd appreciate it.

[ultratec]

You keep saying furnace.. You mean the boiler right? Why does the boiler run? Do you have a tankless coil or indirect water tank off this boiler for your domestic hot water? The boiler is water not steam right? Oil or gas?

[llskywalker]

Is the water line going to that zone filled with water? You might have an air pocket, Possibly a leak. It sounds like your hearing this when the pump is turning on or possibly off.

[patrice]

Sorry for being so clueless about this. Yes, it is a boiler. We have a separate (indirect?) water tank. And it's oil heat. The key to this is that it doesn't happen all the time. The boiler comes on to heat the water and when we had the heat on, it would come on to heat the house, this noise does not happen then. This noise ONLY happens at specific times at 6 hour intervals. It's so reliable I was able to get my repairman to hear it on cue! Is there anything else in this system aside from the thermostats that is timed? thanks again for the replies!

[ultratec]

Patrice, there really isnt anything else "timed" like your explaing like the T-Stats in that system, that I could see from here lol. It sounds like the Indirect ( thats the name for a water heater or storage tank that doesnt have direct means of heating up like oil, gas, electric etcc) Its using the boiler water to exchange the heat to your domestic ( faucet water). There could be alot of things going on, but we just cant hear or see them lol. If you were the service tech, we could help you more. It could be water hammer, an air bleeder etc etc. You said he was there and heard this? He should know what it is, if not, maybe you need another set of eyes and ears down by your boiler.. When the pipes bang, do you feel and hear it at the sinks and in the walls etc? If your water heater has an oil burner firing into it, its not an indirect. If thats the case, turn off the boiler, (its just for heat) and see if the noise goes away.

[Edited by ultratec on 06-21-2005 at 02:40 PM]

[DeltaT]

You probably have a zone damper slamming shut or open in that zone that has been disconnected and the noise stops. And the 6 hour intervals might be due to the timer for fresh air that will cause the blower in the furnace to energize, the outside air damper to open, and all the 3 zone dampers to open (which would explain the noise)for total air flow throughout your home.

Have the tech run each zone damper open and closed to see if that is the noise.

[ultratec]

Originally posted by DeltaT
You probably have a zone damper slamming shut or open in that zone that has been disconnected and the noise stops. And the 6 hour intervals might be due to the timer for fresh air that will cause the blower in the furnace to energize, the outside air damper to open, and all the 3 zone dampers to open (which would explain the noise)for total air flow throughout your home.

Have the tech run each zone damper open and closed to see if that is the noise.

That could be it Delta. With all this furnace and boiler talk, I didnt think they have a Zone damper system, and still dont know if they do. If thats the case, good read Delta.. It may even be the bypass damper if they have one.

[Edited by ultratec on 06-21-2005 at 04:25 PM]

[patrice]

Thanks for all your help. At this point I'll have to relay all these messages to our repairman and see what he thinks. At this point I think I know more than I ever wanted to know about our heating system .... and it's still not enough! But I appreciate all the help and I might be back on once I get some input from our repairman.

[ultratec]

Good luck Patrice, hope you get your problem solved..

[DeltaT]

Do you know the maker of your zone system? Is it a California Economizer, heating only?

[patrice]

Delta, I've spoken to my husband and we don't have a zone damper system. We have 3 separate air handlers for our 3 zones. If you can think of anything else ... Thanks for your help so far.

[DeltaT]

No zoning, three air handlers-- then most all the above...never mind

But you could still have a timer in your home for ventilation which cycle the fan(s). Or, in your thermostat you could have a ventalitaion/circulation cycle and the clunk you hear after the air handle shuts off is "tin canning" from your duct work. But that should me more then obvious to anyone in our field, I would hope.

Tin canning comes from the duct expanding and contracting when the air handler blower starts and stops which pressurizes the duct work.

My bet right now with this new information is "tin canning."

[markco]

Here in our neck of the woods, we call it "oil canning"

[DeltaT]

markco
Whoops! You are right! ..been such a long time since I used that term.

[patrice]

Okay, I'm "canning" and it's not jelly It's 7:55 am in NY and like clockwork my noise just chimed. The ventilation explanation makes the most sense ... since this is not happening for hot water or heat. Where would this timer be for ventilation? It can't be in the themostats because when all 3 are off, it's still happening. And what would cause this just to start the past 2 months? I think you might be on the right track and I will pass it along to my repairman -- who is not an HVAC guy but strictly for the boiler, which might be my other problem. Thanks for all the info!!

[patrice]

Delta, okay, Yea! I think I found it. Got onto the First Co. website and checked out the product manual for what I think is my air handler. And there it is --- pump timer -- energizes pump for 30 seconds every 6 hours. So I'm assuming that this is what is calling for the boiler to turn on and the noise I'm hearing (the tin canning) is when it turns off. Now the question is what is causing the noise -- is there something wrong in the air handling system or in the zone valve in the boiler. Thanks for totally narrowing this down. And again, I now know more than I ever wanted to know about how my house works!!

[DeltaT]

patrice
We are addressing two parts of your heating system. One part is the air side which has to do with moving the heated air.

The other part is you hydronic side which moves the hot water from the boiler to the First Company hot water coil located inside the air handler.

Looks like you have found the cause for the constant 6 hour noise problem with the internal timer. That timer, which should be in all 3 air handlers, is to help keep the hot water pump from sticking from non-use. It's a good thing. But there should be no noise from it or due to it.

So, looks like you have a problem in your hot water circuit due to but not because of the cycling of the hot water pump.

I would now place myself in the area of the noise that you hear when the timer is about to come on. Then chase down the noise to as close to a spot as you can get.

Then it's time for your boiler guy to come back where you can show him what you found. He can move the timer so it will energize and then he can track down what is causeing the noise.

Let us know.