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Rick, HVAC Supervisor
Category: HVAC
Satisfied Customers: 21527
Experience:  40+ yrs. experience as a licensed oil & gas technician.
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I have a boiler with a L8124A, C, L8151A triple aquastat relay.

Resolved Question:

I have a boiler with a L8124A, C, L8151A triple aquastat relay. The boiler heats 2 different buildings, both hot water, not steam. My house t-stat is wired into the 8124A as is the circulator pump, everything working fine on that side. A 2nd building, work shop\mancave has a hydronic unit with fan & seperate circulator pump wired into a TACO SR501 switching relay controlled by a t-stat in that building. When my house circ pump comes on, the boiler fires up within 15 seconds to maintain the water temp presumably controlled by the 8124A. When the work shop heat comes on, the boiler doesn't fire until the water temp drops to the low setting & calls for a hotter water temp. Is there a way to wire the Taco SR501 switching relay into the L8124A auxillary terminals-zone control so that when the shop calls for heat, the boiler fires in the same manner as the house to maintain a hotter temp? This should give me hotter air exiting the hydronic unit with less overall run time.
Submitted: 7 years ago.
Category: HVAC
Expert:  Rick replied 7 years ago.
Hi threshold

Wire the 6N/O and the 5 terminal to TT on the operating control on the boiler. This assumes you are using 3 & 4 to control the circ and there are no line voltage jumpers to 5 or 6.
Customer: replied 7 years ago.

rick, the circ pump is wired to 4 N/O & of course neutral. The house tstat is currently wired to TT on the operating control on the boiler, can a 2nd set of t-stat wires be added to it without interfering with anything? No line voltage jumpers to 5 or 6, only H to 3 on the taco sr501.

Expert:  Rick replied 7 years ago.
TT is a switch leg that will pull the burner in but if you are also controling the other zone's circ with this control then you will also pull the circ in if the SR501 calls so you will need to add a second relay (wired the same way as the shop SR501) to control the circ (and burner control) for the house zone. It doesn't matter if you have 2 switch legs connected to TT. Once the switch is closed it won't matter if another one is closed as well.
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Customer: replied 7 years ago.
Expert:  Rick replied 7 years ago.
Thanks for the offer but your email shows up X'ed out on my screen. They only allow us to communicate through this interface.

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