Zone is heating with no circulation pump on

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Old 01-18-15, 04:02 PM
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Zone is heating with no circulation pump on

Hey all,

I've found a lot of good advice on here over the years, and now I have an issue and am totally stumped.

I have a 2-Zone baseboard heat system / natural gas boiler. Each zone is driven via its own recirculation pump.
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Last night I noticed it was very warm, checked the thermostat and it read 72, the programed temperature was 55. I checked the baseboards and they were warm. I did some troubleshooting today to try to figure out the problem:

Only Zone 1 (Upstairs) is experiencing this issue. Zone 2 (downstairs) is acting normal.

1. Checked to see if there was indication of heat being triggered on thermostat - No indication until I increased program temperature higher than the current temperature. This was normal.

2. Removed power to the recirc pump for zone 1. Zone 1 continued to heat up / moderate at 71-73F. Name:  IMG_1549.jpg
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3. Cut power to the entire unit. Zone 1, finally cooled down, as expected as the boiler wouldn't fire anymore.

All the while Zone 2 remained cold and not circulating.

What could cause Zone 1 to continue to heat up with no recirc pump or control signal? My boiler continues to fire to maintain temperature. All indications are normal (temp and pressure).

Does anyone have any advice? Additional troubleshooting? I am at a complete loss right now.
 
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Old 01-18-15, 04:10 PM
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Welcome to the forums.

You have two check valves in your lines. They keep the water from gravity flowing when the pump(s) aren't running.

Can you give us a pic or two of the rest of the plumbing over the boiler.

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Old 01-18-15, 04:40 PM
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Thanks for the reply. Here is the rest of the system.
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Old 01-18-15, 04:58 PM
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Couple q's Yegs...

Why are there THREE switches at the Taco panel and you say you only have TWO pumps?

It's unusual to wire switches for the pumps... is that something you requested? or did the installer do that on his own?

My boiler continues to fire to maintain temperature.
Why is the boiler firing to maintain temperature if you've got a stand alone water heater?

Is there some reason that you're running the boiler as a 'warm start' ?

All indications are normal (temp and pressure).
What do you consider 'normal'?
 
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Old 01-18-15, 05:02 PM
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These are your 'flow check' , 'flow control', and other names.

They prevent 'thermosiphon' (aka 'gravity flow') from occurring when the zone is not calling for heat.

It's likely that one has stuck open.

First thing to try is a 'rap' with a hammer. Do NOT let your 'inner gorilla' loose on the hammer! You want to give it a good stiff 'rap', but don't just let loose and wail on it...

Inside that thing there is a weighted disc that is pushed up by the flow when the circulator runs. It's supposed to fall on it's own by gravity when the pump is not running. It's probably hung up.

You might get lucky and this never happens again... or if unlucky, the problem could return.
 
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Old 01-18-15, 05:30 PM
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Why are there THREE switches at the Taco panel and you say you only have TWO pumps?
The switches control the Zone 1 Recirc Pump, Zone 2 Recirc Pump, and Main Control Power to the boiler, securing power leaves just pilot light lit. The installation was done prior to me owning the home.

Why is the boiler firing to maintain temperature if you've got a stand alone water heater?
The boiler always seems to maintain the temperatures between 190-210, even when heating is not called upon. I've always felt it was odd, but this is the first system that I have owned, so I don't know any different.

What do you consider 'normal'?
Normal is about 15 PSI and 200F

I can't believe I didn't even think about those check valves, I gave them couple taps and so far everything seems alright. Will monitor it for next few hours / days.
Thanks for all the help
 
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Old 01-18-15, 06:02 PM
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You have a separate water heater do you not? If you do, that boiler should not maintain temp. If there is no call for heat for a couple of hours the boiler temp should drop.
 
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Old 01-18-15, 07:49 PM
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The boiler always seems to maintain the temperatures between 190-210, even when heating is not called upon.
That's a waste of fuel for it to run constantly.

Also, I'm SURE that the temperature control is set too high for your needs.

In this pic:



Across the top there is a white piece of Romex. That's coming from your breaker panel to power the system, is that correct?

There are three 'low voltage' wires. Two are obviously from the two thermostats.

Where is the third one going?

What are the two really white thinner cables? where do they go?

I ask this because it appears that your system has the thermostat wires inside the boiler jumpered to cause it to constantly run, and the controls are only switching the pumps on and off.

That control box has the ability to also control the firing of the boiler.

If you are comfortable with 'poking around' inside both the boiler and the Taco panel we might be able to offer a relatively easy to implement suggestion that would save you some fuel.

Let me know if you have any interest in this and I can walk you through the steps.
 
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Old 01-19-15, 07:44 PM
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The check valve tap seems to have fixed it, at least for last 24 hours. Hoping it was just a fluke.

As for the wiring question: two of the low voltage wires go to the two zone thermostats, the third one goes to the boiler itself.

The two white cables go to natural gas detectors (one is just retired in place) just plugged into an outlet nearby.

As for the temperature the boiler is set to... I just set to the recommended setting for the boiler. I didn't put much thought into it. What temperature should the system be set to?

I would be interested in allowing the boiler to cool down when heat is not called for. I will look for any cabling/control diagrams left over by the previous owner and open up the taco panel and post photos.
 
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Old 01-20-15, 07:54 AM
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the third one goes to the boiler itself.
I'm going to presume at this point that the third cable to the boiler is connected to the ENDSWITCH in the Taco panel.

I just set to the recommended setting for the boiler... What temperature should the system be set to?
Where did you find the 'recommended setting' ? What was the recommended setting?

Typically 180F would be the 'High Limit' setting. VERY rarely should a home require hotter water than this.

What's the model number of the boiler?
 
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