The fireplace boiler wiring has to control the water circulation through the boiler on one side–in the living room, and the circulation through the storage and heat exchanger on the other–in the utility room.
The piping diagram shows some of the wiring logic for the system. I revised the drawing adding a zone valve to the gas boiler side of the radiant circuit so that the water from the heat exchanger only flows when the storage tank is hot enough.
On the boiler side, there is also a Honeywell 8043 zone valve that opens only when the water is hot enough to send to the storage tank–it is wired to a small strap on Grundfos clip on aquastat with a fixed temperature range (95 to 120 F) to send it a signal to open or close. UPDATE: The temperature range of the Grundfos is opposite of what is needed. It turns on at 95 and off at 120. The aquastat needs to turn on at 120 and off at 95!
The zone valve will not transfer the signal to any other device so the red wires will not be used. A 24 volt transformer is mounted in the electrical box to power the valve and the Taco i-series mixing valve and 120 volt power is wired to the pump.
In real life it looks like this:
The boiler circulator/pump will be turned on whenever there is a fire in the fireplace. The Taco iseries mixing valve with sensors on the feed and boiler return will mix water from the storage tank and the circulator bypass to ensure that warm water returns to the stove.
On the storage side several electrical components feed the radiant system from the heat exchanger.
There is a Honeywell 6006 strap on aquastat on the delivery pipe–this is an adjustable aquastat that will either make (the electrical connection, in this case to open the zone valve) on temperature rise or temperature fall. I am using only the temperature rise side. I have added a zone valve that the aquastat will trigger to open when the storage water is hot and close when it cools–initial setting will be a 25 degree differential–on at 120 and above, off at 95 and below–same as the grundfos aquastat. (UPDATE: I was wrong about the Grundfos aquastat–it turns on at 95 and off at 120.) By the way for this DC wiring job I’m using high quality marine grade 14 ga. DC wire, because I bought it for an RV project and have it available.
Ancor 121510 Marine Grade Electrical Standard Duplex Tinned Boat Cable (Flat, 14-Gauge, 100-Feet)
This Honeywell 8043 zone valve on the boiler water side will allow hot water from the heat exchanger to move through the radiant system when the aquastat triggers it to open. The aquastat and zone valve are powered by a 24 volt transformer. The zone valve’s end switch (red wires) is connected to the Taco pump relay so that when the valve opens the circulator pump will turn on.
A small Laing circulator pump will send hot water to the exchanger when it is triggered by the aquastat.
Laing LHB08100085 Low Flow Circulator Pump with Line Cord
I’m working on diagrams and a logic document that I hope will help describe the functions and help me make sure it will all work as designed. There were several mysteries about how the various parts work that I researched and might be helpful if I explained them more thoroughly.