Jumped Taco Radiant Mixing Block (RMB-1) to continuously, is that OK?

Billiambob

I’m Troubleshooting ongoing problems with a heating system and won’t be back for a few weeks. The house is covered in snow and cools (freezes) quickly without heat. I put a temporary jumper wire on the “Heat Demand” input to run the Taco RMB continuously. The boiler loop and associated zone thermostats, valve controls and valves are working normally. The primary boiler loop is 145 degrees and the RMB “Target” temperature is set to 135 degrees. The regulated supply output can get to 130 degrees. All of the thermostats are set to 65 degrees. My question is can the RMB handle it if none of the thermostatically controlled zone valves are open? This would dead head the pump until a zone valve opened. Will or can the RMB protect it self? There is a fuse on the RMB but the pump would be off and house would be cold until I replaced it. Any thought?

Teemok

It uses a constant speed system pump. You don't want to dead head it.

Dave H_2

The heating circ on the RMB is not a variable speed pump, so yes, it will dead head and not have any flow across it. The name "wet rotor circulator" means that it uses the fluid that it is pumping to lubricate and cool the bearing and motor. Without flow, yes the bearings will still be lubricated, but the heat will not be able to leave and cause it to overheat and then cause issues.

As a temporary fix like overnight for a day or two wont cause issues but several weeks can. I would manually remove an actuator on one of the manifolds to allow flow. Pick a zone that is a large zone (most likely to call anyway and one loop in that space won't overheat it even if it is not calling for heat)

What are the issues that you are chasing?

Billiambob

The zone control board, zone valves and associated piping are buried somewhere in the log cabin. The only things visible are three thermostats, 24VAC transformer, and RMB. There is one cable with seven wires that disappear into a hole in the garage. The red and white wire are connected to the transformer. The green and yellow wire are connected to the “Heat Demand” terminals on the RMB. The remaining three wires are not connected. Everything else is hidden somewhere. The rooms do warm up so thermostats are responding and the zone valves are opening. The problem is the “End Switch” circuit is not turning on the RMB. The green and yellow wire on the “Heat Demand” RMB terminals read open circuit even when the zone valves are apparently open. I’m running the RMB continuously by shorting the “Heat Demand” terminals. This is to keep the cabin warm enough to prevent freeze damage. I plan to set the thermostats to 80 degrees and the RMB “Target” temperature to 100 degrees. Room temperatures should not be able to get up to 80 degrees and the zone valves should always remain open.

I will resume searching for the hidden components in a month or two. I think (hope) that the RMB can handle it.