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Old 01-08-2009, 04:17 PM   #1
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Boiler w. Hydronic Air & Honeywell Aquastat

We are trying to understand how Aquastat components work along with our boiler. Unfortunately, Honeywell's 800# is of no real help to consumers.

We have our boiler serviced every year. We have a Weil-McLain oil-fired boiler hydronic air system with a separate Super-Stor h/w tank. It is 2-zoned, so 2 air handlers, one in the basement, one in the attic.

Our questions relate to the AquaStat Relay (L8148A) and the AquaStat Controllers (L4006). The relay is on/near the boiler and the two aquastat controllers are on the h/w pipes, 1 in the basement and 1 in the attic.

What does the relay (L8148A) control and what do the two controllers (L4006) do? You don't need to go into technical terms, just a quick synopsis. The guy in the Sid Harvey store was telling me the controller signals the boiler to kick on at 10 degrees below the controller temp setting.

The relay on the boiler is currently set at 190 and the two controllers are currently set at 180.
I did read that with hydronic systems the boiler, I guess relay in our case, should be set at 200.

We keep our heat fairly low 64-65 during the day and 62 at night (with down comforters on the

My questions are....

1) what is the recommended temp setting for the relay, L8148A based on a hydronic system ?
2) what is the recommended temp setting for the controllers, L4006 ?
3) which should have the higher temp setting, the relay (L8148A) or the controller (L4006) ?
4) is there a recommended differential between the relay (L8148A) and the controller (L4006) ?
5) I have also read here that some people turn the temp down at their heat source during the summer months, if we were to do that, what would the lowest setting be for the L8148A? Does this even make a difference on an oil-fired boiler? We do have a separate h/w tank with a temp setting of its own.

The tech that came for the annual service changed some settings, so that is what I am trying to figure out..why he changed it. We have seen a few differences, but not anything more efficient as he claimed it would be. We actually set it back to the way it was (as stated above).

Thanks for any and all help.


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Old 01-08-2009, 04:21 PM   #2
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The L4006 aquastats may be used to control teh blowers on your air handlers.
Or, they may have installed them as high limits.
Although code would only require one additional limt.

Your service tech should be able to tell you what they are used for.


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