Whistling in pipe when boiler is heating hot water

Mer29

Let me preface this by saying I have a Forced hydro air system. The pipes to the air handler run up to the attic air handler on the same run as the chimney to the furnace which just happens to be behind a wall next to the bathroom in our master bedroom.

Everything was fine until we shut off the heat for the season, that's where the whistling started. You can only hear it when the furnace is on heating the water for the hot water heater.

We had our furnace guy out and he couldn't figure out what the problem was. He checked numerous things on the furnace and nothing alleviated the noise. He ran the water heater without the furnace and we heard nothing (the oil burner heats the water). But when he ran the furnace, we heard the noise on the first and second floors, louder on the second floor.

It's loud enough to be heard when you're sitting several feet away. Since he couldn't find the issue, he suggested we talk to a plumber. A friend who flips houses said it was probably air in the pipe but my furnace guy said if that was the case, you would only hear it when the heat was on and it's not yet.

I'm not really sure which direction to go. We had the chimney looked at early this summer and he said it was clean enough not to need a sweep so I doubt it's the chimney. I'm not sure who to call or who can resolve this issue.

Right now it's not a problem because the furnace runs a few times a day but once the heat goes on, it will run many times a day. I work from home, mostly at my desk in my bedroom and this will make me nuts.

Any ideas would be appreciated. Thank you in advance.

EdTheHeaterMan

I think it is whistling because it forgot the words!

pedmec

Is it a tankless heater, indirect water heater, or storage tank?

EdTheHeaterMan

I actually need to clarify something. You said the when the furnace runs. To be clear, a furnace does not run to make hot water. A boiler may run to make hot water. A furnace does not touch water. A furnace has a flame on one side of a heat exchanger. The air to heat the space is on the other side of the heat exchanger. The furnace is then connect with ductwork to the rooms to deliver the heat.

A boiler on the other hand has a flame on one side of the heat exchanger and water on the other side of the heat exchanger. the flame heats the water and in your cans may go to a coil in the ductwork that gets hot to heat the home, and maybe has another heat exchanger to heat your hot water. My guess is that you have an indirect water heater when the boiler water travels to the heat exchange in the tank to heat the domestic hot water (DHW). But there may be another setup. so it is hard to determine where the sound id coming from

EdTheHeaterMan

Let me reword this to see if it makes more sense

Mer29 said:

Let me preface this by saying I have a Forced hydro air system. The pipes to the air handler run up to the attic air handler on the same run as the chimney to the boiler which just happens to be behind a wall next to the bathroom in our master bedroom.

Everything was fine until we shut off the heat for the season, that's where the whistling started. You can only hear it when the boiler is on heating the water for the hot water heater.

We had our HVAC guy out and he couldn't figure out what the problem was. He checked numerous things on the boiler and nothing alleviated the noise. He ran the water heater without the boiler and we heard nothing (the oil fired boiler heats the water). But when he ran the Boiler, we heard the noise on the first and second floors, louder on the second floor.

It's loud enough to be heard when you're sitting several feet away. Since he couldn't find the issue, he suggested we talk to a plumber. A friend who flips houses said it was probably air in the pipe but my HVAC guy said if that was the case, you would only hear it when the heat was on and it's not yet.

I'm not really sure which direction to go. We had the chimney looked at early this summer and he said it was clean enough not to need a sweep so I doubt it's the chimney. I'm not sure who to call or who can resolve this issue.

Right now it's not a problem because the Boiler runs a few times a day but once the heat goes on, it will run many times a day. I work from home, mostly at my desk in my bedroom and this will make me nuts.


Any ideas would be appreciated. Thank you in advance.

Now this makes more sense to the professionals that can help herein

My guess is that the circulator pump that operates when the hot water tank is needing to recover may be too powerful for the DHW alone. There are pumps that can operate quietly with only one small zone, and also have enough volume to operate when there are many zones calling for heat.

It sounds like you have only 2 zones. One for heating the space by way of the Air handler and the other heats the DHW.

a simple pump change may be all that is needed. try an ECM variable speed pump with a setting for Delta P. that means it will reduce power when the pressure gets too high. This will make the noise go away when only one zone is open.

Now this assumes that your oil fired boiler is using at least two zone valves to determine where the heated water can go. If this is not the case then we need to look elsewhere.

Take some photos and post them here. The boiler from far enough back to see all the pipes from floor to ceiling. And from at least 2 different angles. Three would be better.

Mer29

Ed, Sorry for the laymen's description. I'm not all that familiar with the heating system though I find this whole set up strange to begin with. I grew up with radiators not forced air. This system has always been weird and it grew weirder when we got a new water heater five years ago. I think you are correct in assuming the water heater is indirect. As I said, this system perplexes me. I usually try to familiarize myself with my homes systems but I haven't the slightest with this one, too many working parts. Coupled with the fact that I have two different companies who service parts of the heating system. One company does the furnace and the other does the air handlers and the air conditioners. I'll take some pictures and hope you can give me some insight because I'm not sure who to call to fix this issue and I don't want to spend a mint trying to figure it out. Thank you.

EdTheHeaterMan

Sorry to hear that you have that problem. One of the issues is that there are 2 different mechanical entities that work on your system. You might want to ask around for someone that understands boilers and also does air conditioning. That way you have the whole package being serviced by one entity. And Please stop calling it a Furnace. It is a Boiler. That may be part of the reason you can't find one person to work on both. By using the wrong name for the Boiler, the servicing entity may send the wrong technician to fix your furnace only to find that you have a boiler and that mechanic cant help you.

I was one of those contractors that understood oil burners, boilers and also did air conditioning. In fact, I have your exact system in my former home in NJ. Boiler that makes all the heat. An Indirect water heater that uses the boiler heat to heat the water in the tank . And 2 air handlers with a heating coil the uses the heat from the boiler to put hot air in my home. there is an air handle in the attic for the second floor and there is an air handler for the first floor.

I will send you a diagram of the system so you can better understand your system.

Regarding the noise. I still think my first response was the reason. Many heating and air conditioning systems forget the words to their favorite song and will just HUMMM. Yours prefers to whistle!

EdTheHeaterMan

Seriously, the noise problem, On the bottom of page 18 of this booklet, I used to teach a seminar on this subject, is a chapter that is called The Velocity Noise Problem. It will explain what I believe is the reason for your noise. http://media.blueridgecompany.com/documents/ZoningMadeEasy.pdf
It is able to be tested if you have someone that understands how zoning on boilers works. If you read this booklet from front to back several times, you will become the expert on your system. You can then tell the mechanic what pump you need and solve the problem. You don't want to just buy a pump though. You want to test the velocity noise theory first to be sure a new pump will resolve the problem. It could also just be that one of the zone valves is passing and all you need is a new zone valve.

You may not even have zone valves at all. That is why the pictures would be helpful.

When I find my system diagram, i will post it here.

EdTheHeaterMan

The source of all heat is the Buderus Boiler at the lower left.
The first zone valve opens on a call for heat from AH2 Thermostat
The second zone valve opens on a call for heat from AH1 thermostat
The third zone valve opens on a call from the DHW thermostat
The 4th zone valve is not needed. When it failed about 10 years ago, I left it manually open. The circulator pump for the radiant heat is all that is needed to start and stop flow for heating to that room. That zone valve was installed 4 years before the radiant floor was installed "For Future Use".

As far as the air handler is concerned there is a heat relay in the AH1 & 2 that will activate the zone valve and also start the fan. To prevent the fan from blowing cold air, there is a time delay start on the fan motor(s) so the boiler has time to heat up enough water to warm up the AH hot water coil(s).

If you have questions on how my system works, Feel free to ask here or by sending me a message

JUGHNE

Ed, we can't see the expansion tank.
We know there is one, but OP needs that info to understand more.