Installed New Water Heater But Boiler Still Running?

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Old 07-15-14, 06:41 AM
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Question Installed New Water Heater But Boiler Still Running?

New homeowner here, and I've got a question about my boiler.

So the first project I did was to install a Geospring heat pump water heater, because I dont want to burn oil in the summer.

So the heat pump is working great, but I flipped the breaker to the boiler the next day and the boiler turned on. The guy who helped me install the geospring said it may just be "cycling," it did turn off, but then came back on later in the day. I can feel the capped pipes that we cut from the tankless coil are hot, and so is the pipe coming out of the boiler into the expansion tank. The temp reads 130F. Why is this coming on? All of the thermostats are set to off, and it doesnt seem to be sending hot water anywhere past the expansion tank.

I turned the breaker back off in the mean time. Any thoughts?





 
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Old 07-15-14, 06:58 AM
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The boiler is still cycling because it's designed as a 'warm start' boiler, meaning it's controls will tell it to keep itself warm at the " LOW " setpoint of the boiler aquastat control.

What is the model of the aquastat control on the boiler? It may be a simple (reversible) modification which I can tell you about when I know the model of aquastat.

Most manufacturers recommend NOT capping the abandoned coil on the boiler... something about pressure issues with the capped coil. I might suggest drilling a small hole in the end of one of the caps.

Also, I don't see that the lines from the water heater are 'heat trapped', meaning they would come off the top, over, down about a foot below the top of the heater before going back up again to the home. The purpose of this is to keep the hot water from 'floating' up the pipes by thermo-siphon action. Your heater MIGHT have 'heat trap nipples' built in to the unit and you might not need them.
What does the install manual say about that?
 
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Old 07-15-14, 08:53 AM
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Aquastat

Here is the aquastat, it was set to LO at 180 when I first opened it, I turned it all the way down and took the pic.



 
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Old 07-15-14, 09:14 AM
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Turn the HIGH down to 180F. I'm sure you don't need 200F water to heat your home. You'll save a little fuel too.

You can easily completely disable the LOW control (and the DIFF acts only on the LOW so that will be inoperative also) by performing the following modification which is completely reversible if the need should arise:

 
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Old 07-15-14, 10:30 AM
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Winter time

So this will prevent the boiler from coming on in the summer?

And then in the winter will I want to undo this?
 
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Old 07-15-14, 01:22 PM
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So this will prevent the boiler from coming on in the summer?
Yes. Or, you could just turn it off.

And then in the winter will I want to undo this?
No. When the room thermostats call for heat the boiler will fire up and run to the HIGH limit, just as it did before.
 
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Old 07-16-14, 06:11 AM
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Thanks.

Great thanks so much for the help.

And the capped pipes were just hot because the water for the baseboards was being heated, not because the tankless coil was calling for heat?
 
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Old 07-16-14, 08:28 AM
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Those pipes were hot because they are conducting heat out of the boiler.

I'm not quite sure what you're driving at though?

When the boiler is set up for 'warm start', as yours is/was, in the absence of a heat call from the home's thermostat, the boiler will maintain it's temperature at/around the LOW setting. The CIRCULATOR PUMP will NOT RUN when the burner fires to 'keep warm'.

When thermostats call for heat, the HIGH setting is in affect, and the circulator pump WILL RUN to transport the heated water through the baseboards.

Does this answer question, or did I go off on a tangent?
 
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Old 07-16-14, 08:55 AM
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Yes I see now why it was running, I was just making sure the heat was coming from the water that was being kept hot, and that the coil for the domestic water (which is not supposed to be running at all no that I've got the heat pump in) isn't what was causing them to be warm. Thanks for the help!
 
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Old 07-17-14, 03:27 PM
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Because you went from a tank less to an indirect you still have a low limit set to probably 160. You can turn it down to about 120 but I wouldn't go lower than that
 
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