Current Sensing Relay Mod A50 (24 volt).

[Jim]

I bought a current sensing relay model A50 to assist in control of my add-on humidifier, yeah I have an old furnace.

I installed the senser over the common wire going to the blower motor, at least 8" away from the nearest transformer (it says at least 3" in the instructions). When the blower comes on the humidifier comes on as it should, but when the blower shuts off, the humidifier continues to run, so the A50 is not cutting the circuit like it should. If I shut the main power off to the furnace and turn it back on, then about 4 of out of 5 times the A50 recognizes the power loss and turns off the humidfier. Even if I remove the A50 from the common wire while the blower is on and hold it away from the furnace it does not recognizes the power loss (it must only monitor for spikes/surges).

Per the instructions, "wire lead must carry min of 4 amps for proper operation, if not wrap lead wire around bracket two or more times." OK, right now I don't know about the 4 amps, but if I have to wrap the common around this bracket then I will have to splice it and insert a fews inches of wire. Thats not a big deal, unless I've got a bad senser. Any Ideas?

Thanks, Jim

[Bubba]

Its not the A50. Its the magnetic field produced by your thermostat wiring. You need to replace the thermostat wiring with 17ga braided non shielded wire. You usually have to install a new thermostat too. "It's almost always the thermostat" Bubba

[jamesgangnc]

Just get yourself a small 115v relay and wire the relay coil in parallel with the blower motor leads. Might be able to use piggyback spade connectors at the control board if the motor leads use spade connectors.

[Ernest Scribbler]

"Jim" wrote

Try the wrap. Sounds like you have enough startup current to latch the A50 on, but the running current dropping out isn't enough for it to detect the decrease.