boiler running with no call for heat from thermostat

lindera

I came home this morning, and the house felt like an oven at 72F and the boiler was running. We keep the thermostat at 61. We mostly heat with air source heat pumps so the the 61 is just in case they fail. We still use the boiler for heating our domestic hot water using an indirect tank that was installed on March 1. The boiler fires from a cold start and I if I understand correctly (I'm just learning about this) there are are 2 zones, one for the heat and one for the hot water. Everything had been working fine until today, including using the boiler for the steam heat on a really cold night. At any rate I have turned the boiler off because the house was way too hot. Is this a thermostat failure?

Intplm.

If the boiler is running without a call for heat, it very well could be the thermostat. Has there been any recent work to the system?

lindera

Yes, the indirect water tank was installed March 1, but the system has been working perfectly until today.

Intplm.

If you are sure the boiler is running wild without satisfying the thermostat, ( and it is not your other heating source ) Then you may have a short on your thermostat, thermostat wiring, or both. This would fool the boiler making it think it needs to run.
If the t-stat was changed or worked on , this could be what the the problem is as you seem to have suspected.

lindera

Yes, it's definitely not the heat pumps. I turned them off when I came home, a contractor is here and we were able to repeat the boiler "running wild". He is not sure what the problem is. The thermostat was not changed but if it was necessary to move the wires when installing the indirect tank, that happened March 1. Would the problem just be cropping up now? Many thanks for your help.

Intplm.

Sure ! It could crop up now or at any time. Could just be a coincidence. After a while wires can loosen a bit from there terminals or I have had folks hang a picture in there house and hit the thermostat wire with the nail making the boiler run.
Loose connection? loose wire? crossed wire? old or new minor previously unknown damage? It's hard to say .

Intplm.

It's good you have someone there to look at it. They should be able to figure it out.

Be sure to post what is found ???

lindera

Here's is what the contractor said. He is not the one who installed the indirect. He said after talking with someone more knowledgeable that the whole is wired incorrectly and that there needs to be an aquastat on the tankless coil in the boiler. Currently there is an aquatat on the indirect tank. He couldn't explain to me why it has worked fine for 25 days and is now doing this.

Intplm.

Well if that is what was found then I would not be able to explain that one either.

Maybe we can get another to post their opinion.

ethicalpaul

A funny case of similar problem: https://www.youtube.com/watch?v=SCuBpEWNXec

Intplm.

That sounds like a pretty big short. Not wired correctly. What is the plan now ?

ethicalpaul

lindera said:

Here's is what the contractor said. He is not the one who installed the indirect. He said after talking with someone more knowledgeable that the whole is wired incorrectly and that there needs to be an aquastat on the tankless coil in the boiler. Currently there is an aquatat on the indirect tank. He couldn't explain to me why it has worked fine for 25 days and is now doing this.

Possibly it has been cold enough and/or hot water usage was low enough that the additional runtime on the boiler wasn't noticed.

HVACNUT

We've gotta know the setup.
1st stage HP
2nd stage steam.
Post some pics (not too close) of the system and controls.
The tankless coil in the boiler is being used as a zone to heat the indirect? OK if piped as an isolated hydronic zone.
A switching relay is used for the indirect. Is one used for the burner as well?

EBEBRATT-Ed

Could be the thermostat, could be the end switch on one of the zone valves.

If the indirect has an aqustat that runs the indirect circulator and the boiler. You don't need another aquastat on the boiler with a cold start boiler

Jellis

Adding an aquastat to the coil does not sound right, post a picture of your setup and we can help.

lindera

I will call the original installer. The reason I didn't right away is they are not very local.

lindera

Amusing video! Testing of thermostat shows that it is working. Re outside temps and boiler run time, we actually have not been using the boiler to heat the house at all, just to heat the hot water. Re the set up and pictures, I'm not knowledgeable at all and am not sure I understand the 2 stages you mention (HP and Steam). The heat pumps are not run by a thermostat. I just set them individually according to comfort. The boiler thermostat is set at 61 incase the heat pumps ever fail. I will take some pictures tomorrow. Have to run and get dinner now. thanks for your help. The way we left it for now until the installer can come look at it, is boiler is off and we will run 2-3 times a day for hot water. That will work!

lindera

I misspoke earlier. We have a storage tank, not an indirect. Here are some photos of our set up:

HotanCool

Too many possibilities. Is that an auto feed for the boiler in the back,or do you manually feed? I don't see what maintains boiler temp for domestic, if it's not making steam. If the boiler water line falls below the coil,it may take longer to satisfy a call for domestic, therefore creating enough heat to rise up into the living space. With steam,if a minimum boiler temp is maintained for domestic,you still may experience a little gravity heat at the closest rads. Or, could be as simple as a short. As stated above.

Jellis

ok so here's your problem, i did not realize you had a steam boiler.
Your aquastat on your Hot water storage tank will tell your boiler that it needs hot water when the water in the tank gets cool enough. It will tell the boiler to fire until the water in the tank reaches its set hi limit.

If the temp in the tank is not satisfied before the boiler starts producing steam, that steam will happily flow upwards towards your radiators.
The original installer should certainly take care of this. A control needs to be added to the boiler to control the max temp when only the water tank is calling for heat.
You have not noticed until now likely because your house happily used the extra heat during the colder months.

lindera

Yes that is an auto feeder in the back. The water line is above the coil. We were not using the boiler for heat at all this winter except on the few nights it dropped below 10F outside. We were using only the heat pumps. The storage tank and new coil were installed March 1 and were working fine until yesterday. The temperature in the house had risen 10 degrees above the thermostat setting and boiler was still going when I got home. I don't think it was ever going to shut off . Something was clearly wrong because the average time to heat the storage tank had been about 15 minutes. During a test yesterday even 30 minutes was not satisfying the tank. The thermostat was checked and is functioning. Boiler temp is not maintained. When this setup worked, the boiler fired up when there was a call for hot water or for heat (if we had been using it for heat which we were not). Thanks for all your replies. I'll ask about a control to control the max temp. Original installer is coming Friday.

Zman

Your boiler should have a an aquastat. When there is DHW call, the boiler should fire to the lower temp, probably 160-180. When you have a heat call, the boiler should actually boil and make steam, the pressuretrol then controls the boiler.
It sounds like it is just wired incorrectly. Any competent tech should be able to sort this out quickly.

gfrbrookline

I am totally confused, how many aquastats do you have? There should only be one, most likely in a probe attached to the boiler and it should be set to 160 to allow the hot water loop to be warm enough to heat the hot water in the indirect. You may have a relay that is sticking, I had this problem on my old boiler. While the boiler is firing tap the green box on the right side of the boiler, if that shuts the boiler off you have most likely isolated the problem.

lindera

I have just one aqua stat. It is attached to the water storage tank. I will try tapping the green box to see if it's a relay problem.

gfrbrookline

I am going to rethink what I just said since I just reread one of your posts about it still calling for heat after 30 min and looked at your pictures again. I think the circulator pump is in the wrong place. It is above the waterline and is pulling air into the system when the water level drops that is not letting the hot water flow to the tank. I don't think you have a coil I think you are using boiler water to heat the indirects. The pump needs to be on the return line. I also had this problem, needed to reprime the old boiler a few times a week until we figured out the problem.

JUGHNE

It looks like a dry well on the front of the insert coil. Should an aquastat be there for boiler temp control.
Just a guess, we have none of these around here.

HVACNUT

I dont know what that's supposed to be. An indirect/Aquabooster mutant?
I hate to be the bearer of bad news, hopefully for the installer.
Either the tank needs to be ripped out and an Aquabooster installed, and piped correctly.
Or keep the indirect and pipe it correctly. The heating circuit (the tankless coil to the heat exchanger in the indirect) should be piped like any hydronic zone, complete with backflow preventer, pressure reducing valve, extrol tank, air eliminator, relief valve, etc.
In any case, there NEEDS to be temperature control on the boiler. There is a well in the tankless coil. An aquastat (typically a Honeywell L4006A) should be there to prevent the boiler from making steam when there is a domestic hot water call.
The aquastat on the coil can be set to 160° with a 20° differential. (When the heat is not on, max boiler temp will be 160°, so it wont make steam.)
The aquastat on the water heater can be set to 140° and tempered down to 120° domestic hot with the mixing valve out to the house.
The Taco SR501 currently is using terminals "Common 3 and N.O. 4" connected to TT on the burner primary. The new coil aquastat MUST be wired in series between "Common 3 and N.O. 4.
Have them do right by you because that's pretty shabby right there. While they're at it, ask of they have 6 ft of extra thermostat wire so theres no ugly splice on the side of the boiler.

lindera

Thanks again. Any thoughts about why this worked well for 4 weeks and now is not?

HVACNUT

> @lindera said:
> Thanks again. Any thoughts about why this worked well for 4 weeks and now is not?

No. Absolutely no idea how that piping design is working.
I cant make heads or tails of the piping or what they were trying to do.
The HX in the indirect and the tankless coil should be part of a closed loop (separated from the domestic water) if its supposed to be used as an indirect. It's not. The domestic is tee'd into the heating circuit I think twice. At the mixing valve and upstream of the swing check.
If its supposed to be an Aquabooster, then it's still not piped correctly and it's not the right tank.
But you absolutely need an aquastat in the coil. The boiler is probably running so long and making steam because the way its piped, the water heater takes forever to recover.

Zman

It is just a storage tank piped to the DHW coil in the steam boiler. That's it, nothing more complicated than that....
Someone made a mistake on the control side and it needs to be fixed.

Zman

It looks like they took the aquastat off the boiler so it makes steam everytime it gets a DHW call.

HVACNUT

> @Zman said:
> It is just a storage tank piped to the DHW coil in the steam boiler. That's it, nothing more complicated than that....
>
I dont know what I'm missing. That tank is an indirect. Is it an open loop if it's not isolated from the domestic? I'm confused.

Zman

The boiler has a submerged coil. https://www.tfi-everhot.com/pdfs/TFI_TanklessCoils.pdf
The tank is a storage tank. https://www.heat-flo.com/products/hot-water-booster-storage-tanks

lindera

Thank you Zman and HVACNUT. It sounds like you're not in agreement with what is wrong. HVACNUT, it sounds like you think the system needs to be redesigned.

Zman said:

Your boiler should have a 2 temp aquastat. When there is DHW call, the boiler should fire to the lower temp, probably 160-180. When you have a heat call, the boiler should actually boil and make steam, the pressuretrol then controls the boiler.
It sounds like it is just wired incorrectly. Any competent tech should be able to sort this out quickly.

So would there also be an aquastat on the tank or just one on the boiler?

Zman

You should have an aquastat on both.
When the tank aquastat closes (because the tank temp is low), it should tell the taco switch that there is a call for DHW. The taco then turns on the circ and tells the boiler to turn on but only to a boiler temp of 160-180 (that way it does not make steam and heat the house). Right now, you don't have a boiler aquastat to do that so the boiler fires up and does not turn off until the steam heat pressuretrol tells it that steam has come up to pressure (the house is heating).

Jellis

Oops i did not notice he said it was a storage tank, i was assuming indirect.
Deleted my comment to avoid confusion.

Zman

@Jellis @HVACNUT

It is not an indirect it is a storage tank. https://www.heat-flo.com/products/hot-water-booster-storage-tanks
It says it right on the front. If it was an indirect, it would need ex tanks air eliminator and relief valves ect. It's not!
This is one of the most dysfunctional threads on the site....

lindera

I really appreciate you all taking the time to give input.

Zman said:

You should have an aquastat on both.
When the tank aquastat closes (because the tank temp is low), it should tell the taco switch that there is a call for DHW. The taco then turns on the circ and tells the boiler to turn on but only to a boiler temp of 160-180 (that way it does not make steam and heat the house). Right now, you don't have a boiler aquastat to do that so the boiler fires up and does not turn off until the steam heat pressuretrol tells it that steam has come up to pressure (the house is heating).

Up until yesterday the boiler WAS shutting off once the tank was satisfied. Yesterday the boiler kept running and running way past (I'm guessing) the time that the pressuretrol tells it that steam has come up. The house was 10 degrees higher than the thermostat setting. Would the aqua stat on the boiler be maintaining the boiler water at 160-180 all the time? My hope was that we would NOT be doing that so that we could save energy.

Zman

You can still run it as a cold start. The aquastat and the pressuretrol would just be wired in parallel to the boiler control. The boiler would fire to 160-180 on DHW call. During a heat or simultaneous heat and DHW, it would fire based on the pressuretrol setting.

HotanCool

Zman said:

It looks like they took the aquastat off the boiler so it makes steam everytime it gets a DHW call.

Exactly was I was alluding to. But in the summer,you still may feel a little gravity heat at the closet rads at 160f or even 140f. If so close the radiator Valve. Just remember to open it when needed for heat. The piping from the tank to the domestic coil is a closed loop,should be fine. Just need an Aquastat to maintain boiler temp for Domestic. So,you won't save much Oil usage,but will have more domestic H.W. capacity.

HotanCool

lindera said:

I really appreciate you all taking the time to give input.

Zman said:

You should have an aquastat on both.
When the tank aquastat closes (because the tank temp is low), it should tell the taco switch that there is a call for DHW. The taco then turns on the circ and tells the boiler to turn on but only to a boiler temp of 160-180 (that way it does not make steam and heat the house). Right now, you don't have a boiler aquastat to do that so the boiler fires up and does not turn off until the steam heat pressuretrol tells it that steam has come up to pressure (the house is heating).

Up until yesterday the boiler WAS shutting off once the tank was satisfied. Yesterday the boiler kept running and running way past (I'm guessing) the time that the pressuretrol tells it that steam has come up. The house was 10 degrees higher than the thermostat setting. Would the aqua stat on the boiler be maintaining the boiler water at 160-180 all the time? My hope was that we would NOT be doing that so that we could save energy.

With a New H.W. coil in the boiler,you may get away with maintaining 120f. You can try a cold start,see if it keeps up with demand,you may need a couple of months of no heat demands from your boiler to find out what's best. Maybe try maintaining 100f in the boiler,very minimal temp,and some will argue it's better for the boiler than letting it go cold.