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Thermostat controlling burner instead of aquastat

hundthundt Posts: 5Member
My boiler is set up with what I think is an unusual wiring configuration: the L8124 a/c aquastat has its own TT terminals jumpered, and the thermostat goes directly to the TT on the burner control (R8184G I believe). As I understand it, this has the following effect on the complete system compared to normal cold- or warm-start operation:
Temp < LLLL < temp < HLtemp > HL
No call for heat Cold start: Circ off, Burner off
Warm start: Circ off, Burner on
Modified: Circ off, Burner off
Cold start: Circ off, Burner off
Warm start: Circ off, Burner off
Modified: Circ on, Burner off
Cold start: Circ off, Burner off
Warm start: Circ off, Burner off
Modified: Circ on, Burner off
Call for heat Cold start: Circ on, Burner on
Warm start: Circ off, Burner on
Modified: Circ off, Burner on
Cold start: Circ on, Burner on
Warm start: Circ on, Burner on
Modified: Circ on, Burner on
Cold start: Circ on, Burner off
Warm start: Circ on, Burner off
Modified: Circ on, Burner off
That is, it behaves mostly like a cold-start except that it circulates if and only if the temp is > LL, regardless of call for heat.

I spoke to the guy who set this up (it came with the house) and his rationale was that the previous owners complained about the far radiators still being cold when the heat turns off and he figured he could address that issue by continuing circulation past the call for heat. And the tankless coil just feeds to an electric water heater, so removing the warm start functionality does not reduce the availability of hot water in the house. The manual for the boiler (New Yorker AP-490U) seems to say that it is also available without a tankless heater and in that case it is cold-start, so it seems to be safe to let it get cold.

Am I understanding this all right? Is this something that is done often? Is there some other disadvantage to this setup that I am not thinking of?

Comments

  • STEVEusaPASTEVEusaPA Posts: 2,720Member
    edited December 2018
    It's wrong, very wrong. Have it fixed immediately. The way it is wired, the burner may not shut off when the water temperature reaches the high limit if there is something wrong with the aquastat.
    You want the burner controlled by the aquastat, not by the thermostat.
    This is potentially a very dangerous situation.

    Edit: Let me clarify. It's possible that it is wired in a way that isn't as dangerous as I may have led you to believe.
    It should be wired correctly.
    Another problem is you don't want the circulator constantly circulating cool water thru the system and the boiler.
    Better to figure out why enough btu's aren't getting to where they need to go. Might be low on water, air issue, bad/wrong circulator, etc.
    They do make aquastats with post purge (thermal purge).
    steve
  • hundthundt Posts: 5Member
    edited December 2018
    Hi STEVEusaPA, thanks for the response!

    I actually tested this (by reducing the high limit) and in fact the burner does turn off when the temperature is above the high limit. I should have made clear: the burner is still connected to the B1/B2 terminals on the aquastat, just as it would be in a normal installation. However, the TT is jumpered on the aquastat instead of on the burner control.
  • hundthundt Posts: 5Member
    edited December 2018
    The circulator doesn't actually circulate cool water because of the low limit, though.
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