This summer I re-built the zone valves for the boiler. And I planned new logic for the wiring so that I could include the fireplace boiler and hopefully a chiller. I had the new single pump relay using the output signal for the boiler’s primary pump as well as for the boiler signal to start. With that logic that I only need the boiler and its pump running when the water was not hot enough from storage and do not need it at all if a chiller is running. Although after this fix, the storage pump is still wired to the normally open pump control, I had to move both the primary pump and the boiler connection back to the main zone control board. (UPDATE: Primary pump is now wired back at the boiler and secondary at the zone controller) But for now the boiler wiring is fixed.
The single relay can’t control the boiler as wired above because it has to be powered from the aquastat in order to get the signal that the water is hot enough in storage to use. I tried using the always on connections (NC) and of course then the primary pump just ran all the time and then had no connection to the zone valves.
In order to get the boiler to respond to the zone valves again, I had to change this wiring setup. I could not remember why the pump was not wired to the boiler itself. I knew I had a problem but didn’t remember why. The boiler sends a signal to run the primary pump. I tried hooking it back up to the boiler and running the primary and secondary pumps separately again. But the secondary pump would come on when the valve opens as signaled by the zone controller, but as it started to pull water through the system, it caused a low pressure state in the boiler because the boiler goes through a preheat process before it fires and starts the boiler pump. Lo pressure is an error status and the boiler will not reach its heat stage but shuts itself down. It might have worked to wire both pumps to the boiler signal, but I need the secondary pump to be independent if I want to run a chiller system.
I also managed to connect the wrong white wire and blew the Challenger’s panel fuse not once but twice! Luckily I had a pack of spares and figured out what was making the fuse blow.
Since wiring to the boiler didn’t work, I had to reconstruct the wiring that did work last winter. But even after reading my own post about the boiler wiring, it took me some time to reproduce. I didn’t realize that I had an error in the wiring that I posted. When I tried to hook up the boilers as in the photo, the pump hooked to the priority zone ran all the time. Of course it was on the always closed connection. This wiring configuration for the boilers–at the lower left section of board does not work!
Here is the diagram of the incorrect priority wiring.
So you would think changing this Priority Zone wiring to the always off (NO) connection would switch it when a thermostat called for heat, but this was NOT the case. I have all the dip switches in the off position and only wanted to run the secondary pump from this connection and it failed to come on when the primary pump did. It is wired to the pump connection on the zone control board.
I’m not sure why I had that diagram as the working one, it did not work, but I was saved by the comment in my post that said the pumps were wired in series. I again wired them in series, The black wire goes first to the secondary then the power goes to the primary. The white wire for the secondary is connected to the zone controller and the white for the primary is connected to the boiler. (UPDATE: No longer wired in series.)
I rechecked the installation manual and although it does recommend the primary/secondary piping system, it shows the secondary pump on the relay (and the primary pump on the boiler) which didn’t work for my setup. However, it could be that my secondary pump is too powerful for this configuration and that is why it pulls a low pressure error from the boiler. I have a Taco 009 pump on the primary loop and a Taco 011 pump on the secondary.
With this wiring, even when the fireplace boiler system is in place, both pumps will run when a zone calls for heat. The storage hot water pump will come on when the aquastat reaches the design temperature–about 120 degrees. That will heat the return water from the zones through the heat exchanger. That warmed water will go through the boiler but logically the Challenger boiler would not be firing because the boiler senses when the water reaches the pre-set temperature and shuts down the burner. Warmed water would still flow to the open zones. But of course this fireplace boiler setup is still untested. With a possible addition of a chilling system, the water to the boiler can be blocked off, but then the primary pump would have to be disconnected too.
I also had problems with a couple of the new zone valves. They were calling for heat but not sending a signal to the zone controller to start the boiler. It turned out they had a couple of loose connections, one with a broken wire. I had used the old wires and wire nuts to connect them to the controller so I just had to make a couple repairs and all was well.
It was nice to have the heat on last night when the temperature outside fell into the low 20’s. But we woke up to a pretty warm house at 74 in the living area. So we didn’t really need as much heat as we were getting. I will set the thermostats a bit lower.