A/C fan motor capacitor wiring

[lonestarheir]

Originally Posted by Coco

The A/C is working fine now. I replaced the old single pole contactor with a new dual pole contactor. I'm sure the old contactor was in need of replacing, but when I changed the contactor, it didn't change the "symptom" I was chasing (see below).

After replacing each part (motor, capacitor, and contactor) on the 17 year old York heat pump, I turned on the thermostat from "off" to "cool" and waited for the results. I didn't wait more than about 5 seconds to turn it off again if the fan motor didn't come on, because I was afraid of burning something up if I wired it wrong. Every time I got a click immediately (sounds like an electrical relay), but I have no idea what this noise is. Yesterday, I set the thermostat set temperature higher than the room temperature. Still got a click when I moved the switch from "off" to "cool". I then lowered to set temperature to 10 degrees below room temperature. I then had to wait for about 1 minute (60 seconds) before the compressor and fan motor came on with a much louder click from the contactor. If I hadn't tried it for a full minute, I'd still be looking for the problem with the unit. I have a programmable thermostat, maybe this is the explanation. Thought I'd pass on my experience for any other novice in the same situation.

Thanks for helping me through this one LazyPup. I really appreciate your advice.

Coco

I didn't catch it till you said "heat pump". The clicking that your hear is the reversing valve activating.

[LazyPup]

Although I don't recall ever seeing one that would make a clicking sound, it is quite possible that your system is equipped with a "Delay on Make" relay.

When an AC is off the static pressure within the whole system will be equal to the refrigerant conversion temperature/pressure at the current ambient temperature, which is called "Bottle pressure" When the unit is started the compressor will suck in the refrigerant gas from the suction line causing a drop in line pressure. At the same time the compressor is compressing the refrigerant gas to a high pressure in the condenser coil and liquid line.

If you have a defective fan, dirty coil or restriction the High pressure can go above a predetermined safe operating pressure.

If you have a low refrigerant charge the Low Side pressure can drop below a safe operating pressure that could result in icing on the compressor.

Some High End AC units have both a High pressure cutout and a low pressure cutout switch to shut the system down if either of those conditions is present. The problem is that if a high pressure or low pressure switch turns the compressor off the system will immediately begin returning to bottle pressure, which would reset the pressure cutout and the compressor will attempt to restart again. This conditions is known in the trade as 'Short cycling" and it can potentially be dangerous to the system because when a motor starts the Start current is typically about 3 times the normal run current. This increase in current will also cause a severe increase in Heat in the motor windings. If permitted to continue for an length of time it can result in overheating and burning out the motor. As a preventative measure we then install a 'Delay on Make' relay. When the thermostat signals for the AC to start the delay on Make relay will delay the action from 60 to 90 seconds which allows the motor windings time to cool down before attempting to restart. With this option if a short cycle condition were to occur it insures the motor time to cool before attempting to restart.

Another option, and the one I personally prefer is to use a "Delay on Break" relay as the safety feature. The delay on break relay will permit an AC to start immediately when signaled but when the compressor shuts off it insures a delay before it can attempt to restart. Either type of relay works equally well, but generally a delay on make relay is not even noticed by the homeowner because under normal conditions when a compressor shuts off it would remain off much longer than the relay delay period.

[Coco]

Again, thank you for the help and interest in my air conditioning issues. I'm not an electrician, nor a contractor, just a homeowner who likes to tackle a project now and again. As a result, I don't really know what is going on in the unit.

I have not used the unit in two days now. It is a heat pump, although I never use the heating function. Tonight I stood by the unit while someone else moved the thermostat from "off" to "cool". It's much hotter than the thermostat set temperature. A single click happened instantly. It sounds like a relay, and there is some kind of a relay inside the control panel. In fact, one of the fan motor wires is connected to this relay (the black high voltage one; the other fan wire is connected to the common terminal of the dual capacitor). Maybe that's where the noise is coming from, I can't tell. There was an 80 second delay from this initial click before I heard a softer click (yes, softer - I thought it was louder previously and put this in an earlier post), and then immediately the sound of the fan and compressor starting. From all aspects, I think the unit is working perfectly, and it probably always operated with that delay. I just never noticed, and didn't remember how it worked, since I really haven't used it since last summer.

[LazyPup]

You stated that when you turn the system on you hear a click, then there is a 60 second delay before the unit actually starts.

I suspect that perhaps there is no malfunction here but rather your system is equipped with a "Delay on Make Relay" on the control circuit.

Whenever a motor is started it initially draws approximately 3 times its normal run amperage for a few moments until the rotation is established. That increase in amperage also causes a serious increase in heat in the motor winding. Some high end units have a number of additional safety switches such as a high pressure or low pressure switch that will immediately shut the unit off if the pressures hit a preset limit. When the unit stops the internal refrigerant pressure will return to the at rest static pressure which is properly called "bottle pressure" and it would reset the pressure cut off switch. The motor would instantly attempt to restart again. This is a condition known as "short cycling" and can cause severe damage to both the fan motor and capacitor. In order to prevent short cycling damage they also install a "Delay on Break" or "Delay on Make" relay.

A delay on break relay starts a 60 to 90 second countdown the moment the motor stops but normally when the ac cycles off it will be off for 30 minutes or more and the delay on break relays usually go totally unnoticed, whereas a delay on make relay starts a 60 to 90 second delay when the motor is turned on thus you will see a 60 to 90 second delay from the time you turn the thermostat on until the unit actually starts. This is not a problem but rather it is an additional safety measure to prevent problems.

[HayZee518]

Lazypup - you may be correct in the delay on make relay. The normal circuit breaker that feeds the system will remain closed as long as the loads are applied gradually not all at once! I remember a reverse osmosis filtration unit with a 150 amp breaker that almost instantaneously tripped whenever this thing came on. After installing a 30 second pneumatic timer into one of the motor circuits the breaker stayed closed even when both motors were running. An ammeter check on the three phase line coming into the main contactor showed 400 amps on start up and 140 amps after a sequencial startup using the pneumatic timer.

[suprheat]

Ok finally you spilled the beans...you said it was a heat pump. First off I was wondering why you changed the contactor style from a one-pole to a two? Several years ago compressor manufacturers installed a resister internally in their compressors to act as a psuedo-crankcase heater. The heater will only work by having one leg of power always on - hence the single pole contactor. Not all compressors, however, require this but I would bet if it came from the factory with a single-pole then a single-pole is needed. After all for reasons unknown, a single-pole contactor costs more than a double so I would assume a manufacturer wouldn't just voluntarily put a more expensive component in a unit for the fun of it. Now if your compressor has an external crankcase heater stapped on or wires coming out of a well at the bottom with a heater in it you probably don't have to worry about it. Now you may wonder what a crankcase heater does. It heats the oil in the compressor to boil off any refrigerant that may migrated to the oil sump. If refrigerant is present in your oil then you do not have 100% oil lubricating the moving parts in the compressor thus paving the way for friction and compressor failure. Now liquid refrigerant generally mixes with the oil in lower ambient temperatures, so most A/Cs are fine because most people don't turn them on until it gets above 80 degrees. But some people with allergies turn them on even when it's 70 because they want to keep the windows closed and that's why the psuedo crankcase heaters are on most units now. Then there are people like you who have a heat pump. It runs when it's all the way down to zero outside. All heat pumps have crankcase heaters for this reason. You need to find out if you bypassed a crankcase heater by installing the 2-pole. Otherwise make sure your back up heat is working cause you'll need it. The click you get when you switch the t-stat to cool is the reversing valve in the outdoor unit. It's the thing with a solenoid and 4 copper pipes coming out of it. It changes your outside unit from being a condensing unit in the summer to an evaporating unit in the winter. York normally has a time delay feature built in to their control modules which are located in the outdoor unit. This time delay is usually 5 minutes from the time the unit shuts off - not on. This is a "delay on break" not a "delay on make". "Delay on make" relays are not really intended for applications such as this. It doesn't make any sense for a unit to wait an additional length of time to turn on when it was alraedy off long enough for the pressures to equalize. It would only make the homeowner more uncomfortable because after all the unit wanted to come on because the temp in the house had risen high enough for it to come on. So with a "delay on break" relay, if you had it off for more than 5 min and then turned it on, it would immediately come on. If it was off for 4 minutes and you turned it on, it would come on in one minute. As for the motor the white/brown wire is internally connected to the white wire. It's purpose is to make the motor more versatile to fit more applications - that way a service tech won't have to carry so many parts. Same reason for the leads to reverse motor direction. When it works out for me to use 3 wires instead of 4 (not counting the leads to reverse direction) I simply cut and tape off the brown/white.