Calling all HeatPump Gurus!

[WizeOne]

I have an aging heat pump which normally still works well. A week ago Saturday, during a 100+ deg heat wave, the heat pump stopped. Called the repair man and he came out on Monday. Turns out it tripped the circuit breaker which I never checked because I could hear something humming in the outside compressor unit and just assumed it had juice to it.

Turns out that hum was a low voltage relay that was powered thru the thermostat.

I know that as compressors age they require more juice to start but here is my question. The HP is powered by two 50 amp breakers. The technician said that the HP draws 126 amps on start up. I asked him if that was because the unit was aging and he said no, that was normal.

I also know that HP's use a capaciter to aid in start up and that hot thermostat restarts take more juice than when they are cold. (due to higher head pressures) I do not know how many amps are used once the HP is up and running.

Does this all sound right? I also know that high load breakers can get weak. Mine have been replaced once in 20 years (maybe 6/8 years ago)

Several years ago I had a hot start capacitor added to the system. The technician claims it is not working and showed no inclination to replace it. (seems odd) I guess this 'hot start' capacitor is in addition to the normally supplied capacitor. It would seem that it would be good to have working.

All the technician did, aside from checking all the fluids and cleaning the windshield, was to flip the breaker and extend the restart timer from 5 minutes to 8 minutes.

Yesterday, it was in the mid eighties and the HP, which had been running, tripped the breaker again.

I am inclined to do two things. One, replace the breakers again, and two, find a new technician who will diagnose and replace the hot start capacitor.

Am I missing anything here? Any advice other than to replace the aging unit? I just do not think it is necessary yet.

 

[AltheaToldMe]

Re: Calling all HeatPump Gurus!

Can you tell me the manufacturer and the model number?

 

[WizeOne]

Re: Calling all HeatPump Gurus!

Can you tell me the manufacturer and the model number?

ATM, it is a Lennox, model number HP18-511U-1P

 

[thefairlaneman]

Re: Calling all HeatPump Gurus!

When it turns on and off it also stops the blower motors. A worn out motor can cause it to trip the breaker . I would replace the start up relay/capacitor and see if that fixes it before spending any more money. The blower motors run about 200 bucks each and not very easy for the do it yourself guy.

 

[AltheaToldMe]

Re: Calling all HeatPump Gurus!

There should be a rating plate on the unit and it will indicate the FLA (Full Load Amps) of the unit. I am trying to locate the information, but am having no luck right now.

I replaced the blower motors on my buddies unit at the beginning of the summer. It was not hard to replace them, but getting to them was a chore. The unit had to be removed from a closet to do it. He got replacement motors from Graingers for less then $80.00 each and that included the starter capacitors.

thefairlaneman is right about the blower motors. If they are hard turning, then the amps are going to rocket up when it starts up. The capacitors for either of the two motors may be shot as well. How does the blower sound when you fire it up?

When the tech measured the 126 amps, was that for one leg or both combined? That sounds very high for one leg only.

Here is a document I found for that unit for now:

http://www.lennox.com/pdfs/installation_maintenance/Lennox-HP18-IOM.pdf

 

[WizeOne]

Re: Calling all HeatPump Gurus!

When the tech measured the 126 amps, was that for one leg or both combined? That sounds very high for one leg only.

I assume it must have been combined for both legs.

The blower motor ( I assume you mean the the big fan in the outside compressor unit) was recently replaced. (maybe 5 years)

The spec tag is not easy to cipher. It has an FLA and an LRA header. The fan motor appears listed as 2.0 under the FLA heading and the compressor appears listed as 114 under the LRA heading.

 

[AltheaToldMe]

Re: Calling all HeatPump Gurus!

LRA stands for Locked Rotor Amps. That would mean the MAX amps that a unit would draw fully locked up.

There are 2 blower motors to the unit. The one outside at the compressor and the one indoors that circulates the air. How does the indoor fan work? Does it take more than a few seconds to come up to speed and start throwing air? Does it squeak or make a bunch of noise?

114 amps should be the absolute max that the compressor itself draws on startup even at it's hottest. From what I can find, you have a 4 ton unit and that number is about right.

If you were close, I would have a look at it. I suggest getting a second opinion.

A cheap first step would be to replace the breaker with one of the same rating and capacity. If that unit is pulling that many amps on startup, the breaker may be tired. You mentioned 2 breakers. I would hope that you are talking about a "Double Pole" breaker where when one breaker trips, the other trips as well (or it may be a single handle for both). Some cheap electricians will take 2 "Single Pole" breakers and put a nail between the handles to get them to both trip. I don't advise that. Home Depot should have a direct replacement 2 pole breaker for your application.

I'd also like to know how long that the HP pulls that 126 amps. I'd also like to know what each leg measures after everything is started and up to speed.

 

[WizeOne]

Re: Calling all HeatPump Gurus!

The 'air handler' fan works just fine. It comes on immediately with no noises, squeals or squeeks. The Mrs often sets in on 'on' so that if continues to circulate air even if the heat pump has cycled off.

Is that fan running off the same circuit?

4 tons sounds about right. It is servicing a 2800 sq ft ground floor plus about 500 sq ft, comprising two rooms and a landing up inside the 6/12 pitch full hip roof.

...and yes, it is a 'double pole' breaker.

I will seek a second opinion. I just don't think that the extra hard start capacitor could be a bad thing. When I do maybe I can get answers to your draw questions.

 

[rickdb1boat]

Re: Calling all HeatPump Gurus!

That is a 4 ton unit (51,000 BTU). A hard start kit (capacitor) is normally used on older units that are getting weak and under normal circumstances will not start without tripping the internal overload or the breaker. I've had very good luck with these over the years to keep units going for quite a while. Did they check the charge on the unit? If overcharged it will pull high start and running amps. That number you gave is way out there for a 4 ton unit. It should have a RLA in the area of 12-16 and a start up amp in the area of up to 40. Depending on where amp readings are taken, the fan will put out an additional 2 amps or so when running. The fan draw alone can easily be measured by any tech to rule it out. A 50 Amp breaker is more than enough to handle a properly operating 4 ton unit..

 

[WizeOne]

Re: Calling all HeatPump Gurus!

That is a 4 ton unit (51,000 BTU). A hard start kit (capacitor) is normally used on older units that are getting weak and under normal circumstances will not start without tripping the internal overload or the breaker. I've had very good luck with these over the years to keep units going for quite a while. Did they check the charge on the unit? If overcharged it will pull high start and running amps. That number you gave is way out there for a 4 ton unit. It should have a RLA in the area of 12-16 and a start up amp in the area of up to 40. Depending on where amp readings are taken, the fan will put out an additional 2 amps or so when running. The fan draw alone can easily be measured by any tech to rule it out. A 50 Amp breaker is more than enough to handle a properly operating 4 ton unit..

Although I do not know the numbers, they did check the charge and it is good. My stated RLA amps of 114 came right off the tag on the unit. It did also say the fan FLA amps were 2.0.

To my knowledge, the unit has never tripped it's internal protection. I know there is a little red reset button behing a panel. I did however fry one of the busses on the wall as well as recently tripped the double 50 amp breaker in my panel.

Am I correct in assuming that the 'hard start' capacitor relay kit is in addition the the capacitor that the compressor motor normally comes with?

 

[rickdb1boat]

Re: Calling all HeatPump Gurus!

Am I correct in assuming that the 'hard start' capacitor relay kit is in addition the the capacitor that the compressor motor normally comes with?

Yes. It it wired across the Start and Run terminals on the compressor. It basically turns a 230V compressor into three-phase for an instant...