Regular Guest
Tecman,
Thank you for the reply.
What happens is it seems like it tries to start and then quits and this is very quickly. I was outside last night watching the outdoor unit when it tried to start. I would say the fan turned a couple of revolutions and then nothing. No humming. The digital thermostat blinks cool when you first turn it to the cool mode from the off mode. I think it has a 90 second or 120 second delay mechanism. Then the blower fan turns on and then the compressor starts. At this point the thermostat quits blinking cool and just reads cool. Whne I turned the thermostat to mode=cool it started blinking cool just like it should. Then the lower kicked in after a delay and then the compressor tried to start and the fan outside did the couple of revolutions and then it just quit. I went back in and the blower kicked off and the light went back to blinking and it was ready to go through its delay and try again. The 30 amp 240 volt circuit breaker in the house did not trip. Some folks here have indicated that one of the fuses at the outdoor fuse holder may have blown and to check it.
Mike
Regular Guest
Tecman.
How much difference does the hard start kit typically make on these motors? Is it a cheap enough type of add-on that it is worth trying just as a matter or course. I know we don't discuss specific prices here but I am trying to see if the order of magnitude suggests just automatically adding one for ease of operation.
Mike
Professional Member
Mike:
The hard start will not lower the initial in-rush. What it does is it gets the compressor running faster, wilch will shorten the duration of the inrush to a shorter time. This may help.
What is interesting in your latest comments is that it seems that something is shutting down the unit right away. It could be a controller in the compressor unit (if there is one), or it could be in your electronic thermostat (which you seem to have). What I think is happening is that one of these controllers is resetting, which will set a startup timer of 5 or 10 minutes (short cycle timer). This could be easily due to a voltage dip when the compressor tries to start, causing the controller to detect a power loss and restart the short cycle timer. If the thermostat is the culprit, it is most likely getting its power from a 24 volt control transformer in the air handler. If this is the case, it could be a voltage drop at the air handler, due to low incoming line combined with additional voltage drop at the air handler as the blower motor tries to start.
You could try a non-electronic thermostat as a test to see if it is the electronic thermostat. Solutions to this problem may be as simple as increasing the wire size to the compressor unit or air handler or both. Again trying to get voltage dip readings will point you in the right direction.
paul
Professional Member
Also don't forget that you will have a different control voltage going from 208 to 240. You must change the tranformer wiring. You may not have enough voltage to pull the contactors in.
Regular Guest
stevehvac,
The unit was originally set up to run on 240, then I switched my set-up to 208 and it ran fine. Then switiched back to 240 and it ran fine. So, nothing was changed. I was told by electrical contractor that most modern motors designed for 240 single phase ran fine at 208 single phase.
Mike
Professional Member
If it ran fine then it is a non issue but the eletrical guy is wrong on it makes no differance. It might not matter to the motors but the transformer could give you problems. If it is running on 240 volts and is setup that way then the transformer has the copper going around hundreds of times until it's reduced to 24 volts of control voltage. Now what happens when you have only 208 volts going into the tranformer? Ive found that you may get 22 volts going out. Then after running the t-stat and fan you have 20 volts. Then when trying to run the compressor you have 18 volt which isn't enough to pull the contactor in all the way.Once again it may be a non issue but switching the voltage can have an effect on the control power you have.
Professional Member
and, you may have a pp sine wave from the new generator! = clipped waves
what is the rms voltage? the rms amperage draw? how good is your meter? how many times have you used this meter to read starting currents?
Regular Guest
cem-bsee
I think the meter you are referring to was the meter on the military generator I used to have. I never used it to look at the starting current.
Stevehvac,
I am running the system off of 240 volts now so there shouldn't be a problem with the transformer and 22 volts versus 24 volts. The data plate on the compressor lists the motor as 208/230 volts with acceptable range from 187 volts to 256 volts.
Regular Guest
I checked the fuses at the outdoor unit and both were good. That is they showed a short on the ohm meter. The HVAC techs here where I work believe the problem is in the 24 volt contact side of things. They believe the contacts are making and then breaking and could be a weak coil or thermostat issue. I have a call into the dealer who installed the unit and am anxiously awaiting to get him out to look.
Thanks to all
Mike
Professional Member
Okay...what he was saying was this:Your transformer likely consists of different "taps" on the primary side,one for 208,one for 240.They should match the voltage you are presently feeding in...Originally posted by mikecales
Stevehvac,
I am running the system off of 240 volts now so there shouldn't be a problem with the transformer and 22 volts versus 24 volts. The data plate on the compressor lists the motor as 208/230 volts with acceptable range from 187 volts to 256 volts.
You can check to see if the contactor is pulling closed or not,that should tell you something.
Professional Member
no, I am refering to any troubleshooting meter for use on an electrical system -- should be one which reads the RMS values for alternating circuits -- usually costs more --
what is the control voltage value when the unit is trying to start? the "24v"
Regular Guest
Jacob,
The transformer was set up for 240 originally and that is what I am applying. When I ran the unit off of 208 I did not make any changes ( only out of ignorance that I was supposed to). Then when I switched back to 240 everything was still operating fine. That was last summer. After the winter I switched generators from the old one to a new one and am now having the problem. I wish I still had the old one so I could eliminate one of the two possible causes = generator or air conditioner?
Mike
Professional Member
Originally posted by jacob perkins
You can check to see if the contactor is pulling closed or not,that should tell you something.Originally posted by mikecales
Okay,it still sounds to me like the problem is in the control circuit.Of couse,I am only guessing based on what I read here.
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