I have got a brand new goodman unit. The motor kept stopping after few hours an the tech replaced the motor. It still had same issues.. I was told that the voltage coming into the unit is too high.. The voltage was around 246-249v. The unit itself says it supports a max range of 253 volts. however the motor on the unit supports only 230 volts.. The hvac guy disappeared for 2 days and it is not working out. He suggested me using a step down transformer. Is that the only way out of this? Shouldn't goodman be providing a capable motor that runs in the max range supported by the unit?

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    what country are you in? – Skaperen Sep 17 '15 at 11:08
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    What is a "Goodman unit"? – wallyk Sep 17 '15 at 15:48
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    In the US, "Goodman" is one of the cheapest commonly installed major residential brands. It is affiliated with Amana and Maytag. – user39367 Sep 17 '15 at 18:05

thanks for all the answer guys.. finally resolved the problem. It was due to incorrect wiring.. Explanation from the guy who fixed it.. Instead of plugging in 220 v to the fan, they plugged one end of the hot via the capacitor.. So it was able to run only for sometime till the capacitor drains.. Once it reaches 120 v it is not able to keep up and the fan stops.. I can try to get more details if needed..

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When the nameplate of a motor says 230v, it actually means 230v +- 10%. So the absolute maximum voltage rating of that motor is 253v (10% above nominal). That assumes the motor is also designed for the same frequency power that you have. For example, in the US the power frequency is 60Hz and the motor also needs to be rated 60Hz in that application.

I cannot tell from your question which motor in the a/c system you are referring to. The possible causes of your problem vary greatly depending on whether you are having problems with the blower, compressor, or condenser fan.

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  • Thanks Chris. There is no lack of airflow and the hvac guy is saying goodman tech is complaining about voltage.. Problem with goodman is that I am not able to talk to them directly. I will push the hvac guys more.. – Prags Sep 18 '15 at 11:53
  • Since the unit is new, this sounds like a problem the installer will need to figure out. Barring lack of airflow, the most likely cause of thermal cycling is that the motor is overloaded. If you want any actual help from this end, then you must provide more technical specifics such as the exact model number, a photo of the motor nameplate, a photo of the overall installation. BTW, if you really need a transformer because your local power is nonstandard, then you should consider a buck-boost instead of a step down. They are much smaller and cheaper for this type of application. – user39367 Sep 18 '15 at 15:42
  • Thanks Chris, It is a goodman AC Model VSX130481AC. I will attach pictures shortly. Can you please let me know how much it would cost to setup a buck-boost transformer. Thanks a lot for your help. I am still fighting it out with the HVAC guys and the dealer. They have been postponing it everyday. – Prags Sep 22 '15 at 0:11
  • It appears you may be talking about having problems with your outdoor compressor. However, it seems unlikely that a tech would have "replaced the compressor" in an attempt to resolve this issue. I may be able to offer some suggestions if you provide more specific information. Only a local electrician can price a buck-boost transformer installation for you. Unless you are located outside the US, I doubt that is your problem. – user39367 Sep 22 '15 at 3:21

Ask an Electrician to install a Buck Boost Step-Down Transformer.

They commonly look like:

Buck Boost Step-Down Transfor,er

A common wiring diagram will look like:


Ensure the transformer has an amperage rating that equals or surpasses your HVAC/R Unit. The Electrician doing the install will have the expertise to install the proper one the proper way.

Chris is correct, that induction motors (such as a blower/fan) has a "range" of + or - 10%, and if you are supplying voltage that is within that range, you should have no problem. However, you are supplying a pretty high range to begin with and does not leave very much room for voltage fluctuations throughout the day.

This is also why it is common for a water heater to have a buck boost transformer, to assist with voltage fluctuations for safety and reliability.

There are two main byproducts of electricity: Heat and Magnetism. The longer something runs, the warmer it gets. The warmer it gets, the more resistance on the circuit. The more resistance on the circuit, the lower the current and the higher the voltage. It is a vicious cycle.

I would also ask that Electrician what your power supply is from the utility company. If your voltage is running higher than 220VAC in most countries, and higher than 240VAC in other countries, then something could be wrong and could start effecting other equipment within your home.

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