Electrical question...Ron/anyone

rwbeagles

As mentioned prior we got a new AC unit recently. It's been kickin butt and working great...BUT the inspector for the city came by per usual and said "breaker is too big...needs to be switched out". We had the installers do so...and now I swear it's not working nearly as well.

Now I cannot at all figure out why the two would be connected...and they might not be...but does anyone know a reason why it might be related to the breaker switching out?

Breaker is on, compressor runs, thermostat runs..no breaker trip...air blows out...but it's FAR from cool or even cold like it was. DH is calling the co. back out to looky but I wondered....

Which breaker? You have an ac disconnect outside that looks like a breaker and is actually a specific type, usually an HACR. It's designed to put up with the current spike on start-up. Then there is the breaker in the electrical panel that feeds that disconnect to the ac unit.

On the unit, there should be a nameplate , usually made out of stamped metal but sometimes it's a decal and it will have a place that says FLA or FLC. This stand for full load amps or full load current (expressed as amps or amperes). The disconnect and the panel breaker feeding it should be sized at 125 %. Say, for example, the plate says 23 A for FLA. Then the disconnect and breaker should each be 30 A. The reason is two-fold. First, the start-up current, sometimes called locked rotor current. It takes more current to start a motor from a dead stop than it takes to keep running. Secondly, any device that might run for three hours or more is considered continuous duty and should take no more than 80 % of the current available from the breaker. The funny thing is 125% and 80% are reciprocal of each other. That is, 23 is 80 % of 30 and 30 is 125 % of 23. Also, the wire available should be sized to consider temperature derating considering temperatures it might be exposed to, derating by the temp range of the lugs they connect to. For example, at work, we choose wire size based on 60 degrees Celsius specs (about 149 F). The cheapest lugs one might find in equipment will be no less than that. Also, if the wire has to go a long distance from panel to disconnect and then to the unit, there might be a voltage drop though it should be minimal for about a 100 feet.

The interesting thing is that you said it was working fine with another breaker. Why was it inspected? For insurance purposes or did you have to get a permit for renovations?

Modern AC units will have two capacitors. A regular one that help runs and start the fan motor on the condenser. The second one is called a hard start cap and it is designed to take on a huge charge to help start that and the compressor itself. So, this may help hold down current surge on start up but I'm trying to think of how a smaller breaker would affect the operation of the unit without tripping.

Another question is, even though it's new, how often have you changed the filter in your central unit in the house? I've changed 3 times in two months. I have also just cleaned, after a few months from the previous time, the evaporator coils in the central unit. An ac guy I know on the project I'm at mention some special cleaning spray I can get at a supply house plus a small coil comb to help clean even better than the old toothbrush I have been using. Also, with kids and pets, you are likely to have a lot of dust and fur. So, you may need a cleaning of the evaporator coils. And, we are having daily highs of 100 F or more. During the hottest part of the day, about 102, it gets down to about 75 or 76 in the house but the unit stays running.

Plus, you can hose off dust on the outside unit where the condenser is (that radiator looking thing).

I'm just wondering if these other things have coincided with replacing the breaker with a smaller one. An inspector is likely to look at a breaker as too big if it is more than 125 % bigger than the FLA even though, in the code book, you can have percentages higher than that depending on the motor and duty rating.

When you say smaller breaker, do you mean physical size of the disconnect or less amperage?

More thoughts. If the smaller breaker is not tripping, then it is handling the load.

Also, is your filter in the central unit in the house one of those hypo-allergenic filter out everything types, including impure thoughts? Those things are like trying to breathe through a pillow. What you want is the cheapie fiberglass woven ones (usually blue) that you can get at Home Depot and Lowes for about 45 cents apiece. It's like having a K & N performance filter in your car. It allows the machine to breathe. Also, you may have had a new outside unit installed but when is the last time the central unit was serviced where the evaporator coil (another radiator looking thing) was cleaned. When I first cleaned mine, it may have been almost a decade since it was cleaned. When I opened up the access panel, it was caked nearly solid.

Hey Ron thank you. A/C installers actually called in the city inspector to mind the p's & q's. He said "the breaker is too big...it's supposed to be min 30 and max 35...it's currently 100" if I recall. He worried about it "burning" so he wanted it sized down. It was on the compressor someplace...not the one inside on the fusebox.

Now we think it is freezing up. It's fine if you STOP running it for several hours then restart but tho it's sorta running now the air output is less and the coolness is less. dh thinks there's a freon leak at some point to account for the freezing up when it's far far from chilly outdoors.

We'll see...we're getting them back out tomorrow. House temp is down to a balmy 84 from the high of 88 today!

rwbeagles

It was on the compressor someplace...

That's a new one on me. But then, I'm not an ac service tech, just an electrician who's fixed his own ac and I get hints and tips from Johnnie Allen Plumbing in Denison. If it's some kind of limit fuse or such, maybe there can be a compromise that allows a bigger size.

rwbeagles

It's fine if you STOP running it for several hours then restart but tho it's sorta running now the air output is less and the coolness is less

That's the symptom I had with the evaporator in the inside central unit being caked on one side with dust and fur. I had thought the lines were leaking but when I did have a guy come out and replace the blower motor on the outside unit two years (I had replaced it with the wrong one, initially) I had him check the pressure and it was good.

And my condolences on putting up with this heat. Been there, done that.

But see if you can get the installers to look at your central unit inside the house and have them look at your air filter and the evaporator coils. Also, the motor that blows air pass the cold evaporator can sometimes run unevenly due to build-up of dust, etc. About once a year I clean mine.

ETA:

When I did have that nasty mess on the evaporator, it was freezing up on the clean side, blocking even more air flow.

rwbeagles

dh thinks there's a freon leak at some point to account for the freezing up when it's far far from chilly outdoors.

That's what happened to us after we had a new unit installed. It was great at first and then a few months later, it wouldn't cool down as much. We had them come back out and they were able to find the leak, refill the freon and we haven't had any more problems. That was over a year ago. It was an easy fix, so I hope that's the case for you too.