These are diagrams of the parts and functions for the fireplace boiler wiring.
The storage side is powered by a 24 Volt transformer. Wired with 120 on one side, 24 volt is delivered on the other.
Transformer Wiring
This is one 24 Volt transformer that I bought-not realizing the Taco Zone Valve Controller had its own internal transformers. This is a 50 amp model that I’m using to power the aquastat and valve.
Plate Mount Transformer
This is the diagram of the Honeywell 8043 valve. It has four leads, two yellow and two red. The yellow are the power lines and the red are the end switch that can be used to trigger another action. On the zone controller the red are wired to turn off the zone valve lights when the valve closes. A 24 volt current is sent when the valve is open and turns off when it closes. The valve can also be opened manually, but the end switch only operates if the valve is opened by current.
Honeywell Valve Diagram
Although the aquastat is controlling a pump in this diagram, the wiring to the valve is the same. The hot side is interrupted by the aquastat, when the aquastat makes the connection, then the circuit is on, when the connection breaks then the circuit to the valve turns off.
Simple Aquastat Wiring
This is an explanation of the aquastat wiring for W-R-B terminals. I am not using the R-B terminals.
Aquastat Function
The Honeywell 6006 aquastat is controlling the valve using the yellow power inputs. The red wires are sending a 24 volt signal to the pump relay. This aquastat works with either 120 volt or 24 volt power–something that was not clear in the documentation.
Honeywell Zone Valve Wiring to Taco Relay
A powered signal from the aquastat to the pump relay requires the alternate relay wiring. A thermostat wire connected to the relay instead would be getting its power from the relay’s transformer and would be wired to the RW terminals, however, the valve must be powered on the yellow side and an external transformer is required. So the W and 24 V/COM terminals on the pump relay are used and 120 VAC is not connected to the relay’s transformer.
The pump relay has both a normally open (N/O) and normally closed (N/C) circuit that can be used when the valve is open and when it closes. Normally closed means the circuit is delivering power except when the valve is on. Normally open means that it will only deliver power or close the circuit when the valve is on.
The storage pump will be on the normally open circuit, it will only come on when the aquastat is letting the valve open because the water in the tank is hot enough to circulate instead of heated water from the boiler. The boiler pump and firing circuits will be normally closed, they will only open when the aquastat sends the signal that the storage water is hot enough to circulate, the valve will be closed and the boiler will operate normally.
The primary pump wiring should remain the same, i.e. wired to the zone control instead of the boiler. The boiler signal from the zone control will have to be interrupted by this set up too. That would avoid having the call for heat sent directly to the boiler. Although not shown below, I believe that it will be wired to the TT connections on the Taco switching relay next to the T and COM ports. That will transfer the signal to the 24 volt side of the relay and connect to the TT on the boiler, where the circuit is normally closed (or ON) unless wood heated water is being circulated to the system instead.
Taco 501-4 Switching Relay Alt 24 V Wiring. UPDATE: The boiler pump can’t be connected like this–moved back to the main controller.
The boiler side also has a transformer for the valves too. I found another one at the Restore that was brand new in the box for $3. It was not plate mounted so I bolted it to the box cover.
Transformer Wiring
The transformer is wired to a Honeywell 8043 zone valve that opens when the Grundfos pipe aquastat reads that the water in the bypass line is hot enough to send to storage. UPDATE: The Grundfos aquastat is set to turn on at 95 but it also turns off at 120, so I had to replace it with the Honeywell high/low aquastat.
This is a one way aquastat unlike the Honeywell 6006, it makes and breaks on only one circuit but the Honeywell can make or break either as a high temp limit or a low temp limit.
Grundfos Clip On Aquastat–Temp. range does not work!
The Taco Mixing Valve is also wired to the transformer–there is no integrated end switch. (An end-switch makes or breaks to indicate positive proof of equipment position being ON or OFF such as with a damper or valve.) There are only two sensors hooked up the Taco i-series valve, one is the boiler supply sensor, and one is the boiler return sensor. The fireplace boiler will not operate steadily enough to use a setpoint or outdoor reset sensor. The sensors will work together to determine the amount of water each pipe will deliver to optimize the water temperature going back to the boiler.
Taco Mixing Valve Wiring
The Taco 006 stainless pump on the fireplace boiler is wired directly to 120 and the entire circuit will be controlled by a light switch in the utility room that will be manually turned on when the fireplace burner is started. I’m planning to put a timer on the circuit so that it can turn off without being monitored until the end of the heat cycle.
This is the logic behind the operation of the stove.
Fireplace Boiler Logic Diagram