50 ampto 60 amp breaker


Old 09-09-06, 01:26 PM
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50 ampto 60 amp breaker

Lights are dimming when air conditioner and heat first come on. I had a Tech check out heat pump and said everthing was fine. Said heat pump started up at 49amps and suggested to change breaker from 50 to 60.

Would this be safe and could it possibly be something else(such as a breaker going bad?...just switch to another 50amp.

Any suggestions....Is this an electrician problem or Heating Air issue?
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Old 09-09-06, 01:40 PM
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If the unit is not tripping the breaker, you have no problem in that area. Breakers are already designed to allow starting loads.

You also cannot swap breakers unless the existing wire is oversized or replaced to allow for the bigger breaker.

Dimming lights (briefly) can be normal when heavy loads are applied in other circuits.
Old 09-09-06, 01:45 PM
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Changing the breaker will do nothing, except create a fire hazard if the breaker exceeds the wire size or the manufacturer specifications on the unit. It will NOT help or hurt the dimming of other circuits in the house.

As Mac stated, some dimming is normal and to be expected when a heavy load starts up, and 49 amps at 240 volts is a heavy load.

If the dimming is excessive, not brief, or happens when the unit is just running, then you should be concerned.
Old 09-09-06, 01:56 PM
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I would assume that this is wired to the main panel.What size (main breaker) is the service?
What else may be running?
This sounds normal, You may have a slite inbalance on your phases.
As stated, if this occurs on start up and only lasts for a few seconds, Don't be alarmed.More than that you would want to address it.
Old 09-09-06, 02:24 PM
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I do not see how an imballance could have anything to do with this.

I do think that a starting surge is causing a momentary voltage drop. I say it is probably normal.
Old 09-11-06, 11:13 AM
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Most HVAC equipment will have a special rating on the nameplate which will specify the mfr's. recommended breaker rating. It is usually designated as "MOP" or "Max OCD", which stands for maximum overcurrent protection device. Do not exceed that rating.

If this rating is not listed on the nameplate, look for an "FLA (Full load amps) of the motor. The NEC specifies that you multiply this number by 2.5, and you may round up to the next standard size breaker and no further. But you are permitted to round down.

But listen to these guys - don't ever up a breaker size without increasing the wire size to the max amperage allowed by the NEC for that breaker. That's a fire waiting to happen.
Old 09-11-06, 01:09 PM
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There is some possibility that it maybe related to start up time on the compressor. Some tech's I know advocate hard start kits to stop winking or dimming of house lights when the compressor starts. I am not a HVAC trained person so I dont have documentation whether this can be damaging to the compressor. However I'm told that all single phase air conditioners used to come with these but cost and some other factors stopped their use as factory installed equipment.

Now I had this same problem of dimming on my lights when the a/c started. I installed a hard start kit as recommended by a hvac tech as a possible solution to low voltage causing the dimming during compressor start-up. Though it did not 100% cure the dimming it reduced to the point it is barely noticable.
My understnding also is the higher SEER units are more likely to cause light dimming.
I have had no problems with my ac since installing this kit some time ago.

If the dimming is severe then probalby should explore other causes but this hard start kit worked for me.

Old 09-11-06, 01:23 PM
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Actually, lights dimming when an A/C or fridge come on is fairly normal in a residence. The inductive inrush in the compressor causes a house-wide voltage drop. I haven't seen any damage resulting from this.
Old 10-04-06, 05:09 PM
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I talked to an electrician(but have not had any luck with actually getting one to come look at service). He did say that changing to a 60 amp would not cure the problem and would be a fire hazard. Power company came and did change out transformer and ran new line to house. A little better on start up but still having light dim at heat pump start up.

Is 49 amps to much draw on start up on heat pump? I was wondering if I needed a second opinion from another Heating/Air Teck?
Old 10-04-06, 07:41 PM
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Roger wins the prize for the most effective solution.

Residential a/c uses a PSC type starting system for the compressor which is just a simple run capacitor bleeding a small amount of current to the start winding.
The hard start kit that Roger referred to is a combination start capacitor/solid state relay.
When the compressor starts it applies full current to the start winding with the added power of the stored energy in the start capacitor.
It is very simple to connect in that there are only two wires that connect across the existing run capacitor.
This more robust start will as said, bring the compressor up to speed faster reducing the time the high amperage start winding is engaged.

One other thing to look at is that if your system is oversized it will cycle more frequently making dimming more noticeable.
Old 10-05-06, 11:54 AM
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Yup, have the HVAC guy install a hard start kit. That should minimize the problem and it is not damaging to the compressor.

Some electricians also believe that placing the breaker for the A/C unit (and all heavy loads) at the top slots (or slots closest to the main breaker) in the CB panel helps. Certainly wouldn't hurt.


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