Ask Me Help Desk - Double breaker?

Hi, I have recently put in a new 200 amp. Service and had to install a large J-box to extend the wiring to the new location, (not very far). My problem is that I have a new 2-pole 40 amp. Breaker for the "A/C", and a 15 amp. Breaker for the "furnace". My confussion is that either of these breakers will shut down the condenser but if the 40 amp. Breaker is "off", the 15 amp breaker will only "click" when you flip it to "on"?? So.. it seems as though I might have the wiring wrong? Can anyone offer me a suggestion as to where I need to start to trouble shoot this problem, or maybe this is something that occurs because of a simple wiring mistake? Thanks to anyone who knows about something like this. Thanks kindly, Bruce

Quote:

Originally Posted by bkchain

Hi, I have recently put in a new 200 amp. service and had to install a large J-box to extend the wiring to the new location, (not very far). My problem is that I have a new 2-pole 40 amp. breaker for the "A/C", and a 15 amp. breaker for the "furnace". My confussion is that either of these breakers will shut down the condenser but if the 40 amp. breaker is "off", the 15 amp breaker will only "click" when you flip it to "on"??? So..., it seems as though I might have the wiring wrong? Can anyone offer me a suggestion as to where I need to start to trouble shoot this problem, or maybe this is something that occurs because of a simple wiring mistake? Thanks to anyone who knows about something like this. Thanks kindly, Bruce

The 15 and 40 should be separated, the 40 ONLY provide power to the fan and compressor and the 15 provide power to the fan (indoor coil)and the control circuit for the whole system ( including the relay( 24v) for the40). Any breaker trip the compressor won't come on... which wire did you rerun?

Thanks so much for contaccting me. I had to install a Large J-box which is where I made all my slices. I brought out every wire that was in the original 150 amp. Panel. I forgat to mention a few things. First, all the lights in the house dim slightly when the A/C condenser kicks on! Also I do have the "neutral" tied to the neutral buse? Maybe I don't need the neutral to be connected at all?? BOTH the 15a breaker and the 40a 2-pole will EACH shut DOWN the compressor, BUT then.. when I trip the 15 and also trip the 40, the compressor will only "click" when I flip the 15 back on?? Could it be the "neutral" on the "neutral buse", could be creating some sort of instant surge from the 40a breaker wiring. Could this also be what is instantainiously dimming the lights at start up? Any advise you may have would be greatly appreciated. Kindly, Bruce

Trying to understand what you mean by "trip". If you mean just to shutoff each breaker to notice the effect of two breakers shutting off the compressor is because the 2 pole 40 is the main power for the compressor, and the control voltage is supplied by the furnace circuit.

Leaving the 40 off and the 15 on leaves the control power on in the compressor, and the clicking is the relay opening and closing, which is controlled by the thermostat. The thermostat gets its power from the furnace.

AC compressors normally, at least back when I wired a few hundred, did not need a neutral, but new ones may.

The lights blinking is not any cause of the compressor neutral, but is caused by the heavy starting load of the compressor, and is an indication of a possible serious problem.

One is a loose connection in the main panel, meter, or even the utility lines outside. Or it can be caused by a long utility line that is too small. It may had been sized for a smaller laod, and if the AC is a new load, the small wire may have a voltage drop.

Sounds as if your HVAC system is fine, but you should have your electrical system checked for the problems I mentioned. A loose connection will only get worse and cause something , either the panel, breaker, meter, something to be badly damaged.

Just sent a guy out tonight to bypass a badly damaged disconnect switch for a large chiller that cools an MRI system that brought a medical facility to close, all because of a loose connection. Had they scheduled our preventive maintenance we would have saved them from the outage with our infrared camera, ultrasonic sensor, and a millivolt meter.

The lights blinking means a low voltage condition, and the compressor motor will can be damaged due to low volts.