AC Low Voltage Protection.

[Gjac]

I had read a while back about AC's having built-in protection from low voltage by having a switch that cut off the AC before damage occurs. Does anyone know more details than this, and where it is located and what does this switch look like.

[Gjac]

wa8yxm wrote:
However when the Thermal Cutout (no matter the brand name) Cuts out...The motor is ALREADY OVER HEATED. And thus Damage has been done.

Plus there are more things than windings that can "Burn out".

Low voltage is a motor killer.

Why bother putting these thermal switches in if the motor overheats and is damaged by the time the switch shuts of?

[chuckftboy]

Old Biscuit is correct that when a Klixon thermal-disk is used on a compressor, it opens on temperature. Klixon is a brand name and they also make other compressor controls such as pressure switches and relays. Temperature goes up when amperage increases due to low voltage but a thermal disk will also open when the compressor shell gets too hot from reduced air flow, low refrigerant, ect.

[wa8yxm]

However when the Thermal Cutout (no matter the brand name) Cuts out...The motor is ALREADY OVER HEATED. And thus Damage has been done.

Plus there are more things than windings that can "Burn out".

Low voltage is a motor killer.

[Gjac]

Coyote74 wrote:
I have a 2004 winne adventurer with basement air. I also use a surgegard protector. I was in a park and low voltage happened where air was running and I was outside getting a extra chair out for guests and I smelled plastic burning.apparently the power was down to 104 or 105 volts about an hour and the damage happened.The ac burned up 2 run capacitors, a printed circuit, and 2 start capacitors. The wire harness had to be replaced too.
the surgegard doesnt cut low voltage until 102 volts. Anything under 108 can damage appliances.It did mine. Now I own A huges autoformer to increase voltage when needed.I now use them both autoformer at the pedestal first and then surge gard just before the MH plug.now its protected!

. That's why I asked if these switches could be bought to shut off at 108 v. They seem a lot cheaper than the surge guards. I have heard several people say their surge protectors did not protect them from this kind of low voltage. I am not sure how quick these switches work but it sounds like if they shut off fairly quickly you could add one that would cut out below 108 v and over 130v and your AC would be protected or even add one to your main power supply to shut off all the power to the MH. Am I missing something basic here?

[Coyote74]

I have a 2004 winne adventurer with basement air. I also use a surgegard protector. I was in a park and low voltage happened where air was running and I was outside getting a extra chair out for guests and I smelled plastic burning.apparently the power was down to 104 or 105 volts about an hour and the damage happened.The ac burned up 2 run capacitors, a printed circuit, and 2 start capacitors. The wire harness had to be replaced too.
the surgegard doesnt cut low voltage until 102 volts. Anything under 108 can damage appliances.It did mine. Now I own A huges autoformer to increase voltage when needed.I now use them both autoformer at the pedestal first and then surge gard just before the MH plug.now its protected!

[Old-Biscuit]

jhilley wrote:

Old-Biscuit wrote:
Actually the 'klixon' is a thermal overload

No, it is a temperature rated pressure switch.

Klixon HVAC Pressure Switches

Klixon used for both PLUS.........LINK

As used on RV A/C Units....compressor motor 'thermal-0verload'.....LINK

[jhilley]

Old-Biscuit wrote:
Actually the 'klixon' is a thermal overload

No, it is a temperature rated pressure switch.

Klixon HVAC Pressure Switches

[Old-Biscuit]

Actually the 'klixon' is a thermal overload

[camper19709]

Never heard of that. I use a Hughes Autoformer.

[jhilley]

Those are pressure switches for high pressure and low pressure cut-out.

[Gjac]

Good Sam RV Club Member

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Posted: 03/17/15 11:17am Link | Quote | Print | Notify Moderator
"there is a thing on every air cond compressor called a klixon that heats up at the same rate the windings in the motor do. If in a brownout period the voltage goes down, then the amperage goes up. Fact or law of electric. the klixon will snap off until it cools and then snap back on. It should (repeat should) prevent the AC from turning to toast.If you hear the compressor cycling, turn it off.For best insurance, buy a Progressive EMS and it will turn off the electric for you. Absolute peace of mind for a couple hundred bucks."
I found what I read a while back copied above, I had not heard this before either but found it very interesting. Apparently Klixon makes a lot of switches. Sounds like if you could put one in that shuts off at 108 volts the AC would be protected from low voltage, I was hoping some electricians could comment.

[2oldman]

Never heard of that on an a/c unit.

[wa8yxm]

I too am not aware of any such Air Conditioner.

I have a Hughes auto-former.. This device will boost low voltage if it can,, and if it can not boost enough then a Surge Protector such as the Progressiv Industries job in the last post.... Very good product.

[Old-Biscuit]

Yes an EMS will protect from low voltage/high voltage events by cutting power off until voltage is back within limits----103V t0 132V.

Problem is AC motors can incur damage at 108V.

I have a Progressive Industries unit and it has found 'reversed polarity', 'open neutral' and has cut power during low voltage excursions BUT I actively monitor AC voltage in rig and I shut down AC when voltage is low at 108V.

Need be I'll run generator until voltage improves.