Aquastat, Air handler blower fan and thermostat issues...


Old 12-29-15, 05:16 PM
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Aquastat, Air handler blower fan and thermostat issues...

Hello all, trying to do some troubleshooting. I have an oil furnace, domestic water heated by the oil furnace and 3 air handlers with coils heated by water heated form oil furnace. The aquastat on the water tank is set to 130 (works fine for my water needs). I just raised the oil furnace lo and high switches from 120/140 to 140/175 (cold day today). Each air handler has an L6006C Aquastat. Today changed the setting on the air handler aquastats from 140 to 160 and the differential from 10 to 15.

I installed 3 new thermostats and have had many issues with them. Finally have them somewhat working. My current problem with one was that with the fan in auto mode, the blower kicked off around 65 degrees with heat still being called for and indicated. Todays tests (with the new temps above) with the fan placed in ďonĒ, showed me that it is capable of getting to a higher indoor temp, so I think the problem would then either be with the wiring of the thermostat (but if thatís so, then why does it function correctly in auto mode below 65 degrees?), or more likely, something to do with the aquastat and possibly the differential.

I am not a plumber, electrician nor HVAC, but am a GC and did install all 3 coils and both the furnace and the water tank myself (yes, a few minor mistakes made☺), but I am also on a big learning curve because I came from a part of the country where we donít have a need for any of this.

I found this article to be quite educational:

Gave me a basic understanding.

Tomorrow, I will call Honeywell support and see if they have any ideas.

While I am at it, do these temp setting sound ok to you all:

Domestic water 130 (not a lot of demand)
Furnace LO:140/high175
Air handler aquastats: 160, differential 10

Domestic water 120 (not a lot of demand)
Furnace LO:120/high140
Air handler aquastats: 130, differential 10

Maybe someone can also educate me on the simple working of the following:
I do NOT know the relation of the high limit on furnace to the air handler aquastat, but assume that if I have the aquastat set to 150, with 10 diff and the furnace reads 170, that when a demand for heat is called for, the furnace would not need to kick on, while the blower would because the temp is already satisfied. And conversely, when furnace reads 150 and the air handler aquastat shows 170, with diff of 10, the furnace would have to kick on with a demand for heat to get to minimally 160 to supply heat. In this scenario, when would the furnace kick off? When it reached its high limit or 180 degrees?

The low temp limit on furnace seems to just stay at 140 even if the dial is increased. Guess its some sort for protection.

Thanks all.
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Old 12-29-15, 05:29 PM
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Welcome to the forums.

I moved your post to the boiler and hot water forum. You have a boiler and a hot water loop type system. A furnace is hot air.... no water involved.

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