"A tip for whole house generators and A/C compressors"
Column #899 06/02/12
On The Level
Q. I'd like to see you do an article on whole house generators. Those that run on propane or natural gas, are hooked into the home electrical and will provide power in event of a power failure by the electric company. We've had one for a few years and not until last year, ran into a problem that was not foreseen. We had a power outage for 4 days late last summer and the generator ran non-stop. It's a 13Kw unit and more than adequate to cover our basic needs of refrigeration, lights, specific electrical outlets and heat and air conditioning. The problem was the air conditioning compressor. When it cycled on, it pulled so many amps getting spooled up it created an inordinate amount of heat in the generating unit. This "lugging down" of the generator was evident by dimming lights and a labored sound of the generator. Once it got spooled up, everything was fine. However, repeating this cycle numerous times in the 4 days caused the plastic wire nuts in the generator to melt from the heat and the copper windings began coming loose and breaking. We ended up having to replace the generating portion of the unit at considerable cost.
We found out at the time that our Trane A/C lacked a capacitor to alleviate this problem. Newer models now have the capacitor, called a Hard Start Capacitor (HSC), factory installed. We had a Trane after-market HSC installed and now itís barely noticeable when the A/C compressor cycles. The generator doesn't labor and there is little dimming of lights.
Would you point out to those people who have, or plan on getting, a whole house generator, to ensure their A/C compressor, if it's more than a few years old, has a factory installed HSC. If not, they should get one. The HSC functions to lessen the amp draw at startup thus preventing overheating the generator. If you do research, as I did, you will find HSC prices vary from around $30.-$200. The less expensive ones are called "firecrackers" by the Industry and will help but in my opinion it would be best to get one specifically made for your unit. It takes less than 15 minutes to install. Thank you for your consideration.
A. Thanks for the tip and Iíll sure pass the information along but your message contained a few things between the lines that Iíd like to discuss. I can tell from your description of your back-up energy system that it was professionally installed, that the installer was a true electrician who probably (I hope) pulled an electrical permit from your municipal Inspection and Permits Dept. to install the unit. The most important feature of a system such as yours is a thing called a transfer switch. The transfer switch locks out your panel that has the main breaker from the power company and there is a separate panel for those items identified for power when the main power is out. Not having such a thing can and will endanger the lives of those utility line workers up on the poles trying to restore the storm damaged electrical distribution system. Improperly connected generators will send lethal current out onto the line coming in from the utility and can and has killed repair workers.
I see thrifty idiots back-feeding their main panels with contractor job type generators attached to the house via a dryer plug outlet. Itís not only against code, itís highly dangerous and those clowns poo-poo me when I make an issue of it. My final comment to them is to ask them if they can spell ďwrongful death lawsuitĒ because oneís just waiting to come at them.
The other item I spotted when you said your A/C unit was laboring from the compressor upon start up is-- and you alluded to it-- the age of your unit. I was discussing this with an electrician friend and he smiled and said those capacitors have been routinely installed for about twenty years now which tells me your compressor is really old. I donít know how much it cost you to repair your damaged generator but I can tell you that was money that could have gone to buying a new air conditioning compressor. That old unit of yours is eating your wallet slowly but surely. To most folks the good news is itís still working. To me, the bad news is itís still working. If itís pulling that hard on your generator, imagine itís pulling that hard on your electric bill each time it fires up. Consider replacing it with a modern SEER 13 unit or better.
The function of the capacitor is it stores a jolt of electricity that discharges upon start up giving the motor of the compressor a boost to get going. In some units if the capacitor goes bad the motors may not start. Older units had fuses that were designed not to burn out with the surge upon start up. The capacitors really help the newer units. Capacitors themselves can be dangerous storing that jolt waiting for use and I know of people who have been killed by them while working on refrigeration motors. Everything comes at a price.
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