A/C question

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Rockyd

Rockyd

Senior Member
Location
Nevada
Occupation
Retired after 40 years as an electrician.
High energy bills are invading friends house. Went over and checked panel, all connections clean. No new appliances added.

Winter has arrived (location is north of Las vegas,NV) so took readings on heat pump. Reading about 36 amps on a 4 ton unit (think it's a 4 ton) and that is what the info on the side of the unit indices as running amps. Does this seem about normal?

Bill is $300+ or so a month at new rate. Has been about$125 to 150. Is this just sticker shock for an area that is about 50 degree days, and 27 degree nights? The cost per Kw is 12 cents.
 
PS ...Am at HO's computer, at house with the high heat bill problem. Anyone there to verify if the information is about what it should be?
 
If a 36 amp, 240 volt load ran 24 hours a day for a month, the bill would be,
36 x 240 x $0.12 x 24 x 30 / 1000, or $746. If it ran for only half the time, the bill would be $373. Add this load to the other house loads, and a monthly bill of $300 does not seem out of line.

What has recently changed? Utility rates? Weather conditions?
 
Also, is the most recent electric bill handy? Is there anything there about an increase in usage (some utilities show a graph of you last few months of usage)? Any other clues in the bill?
 
Weather has been unseasonably cold last half of heating bill cycle, and think the automatic stat program may have been set, vs what the HO would have had as a usually lower setting. The house is ran strictly on Heat pump, or if there's heat strip involved, it is well hidden, and without a manual switch.
 
I have also seen time were the KW usage was calculated or estimated, rather than read. This caused a few "unusual" bills, that balanced out later when the meter was actually read.
 
and they say heat pumps are the best..I spend less than a 1000 per year to heat my pad in the frigid north and I do not use wood..Just say no to heat pumps..hermatic refrigeration units are not economical..
 
Rocky are you talking about the condensor unit that is drawing 36 amps. or the heat strips in the blower?

The condensor unit will probably be protected at no more than 30 Amps. so it shouldn't draw very much ( check name plate rating)

There are different heat strip kits that can be installed in a heat pump. and they will kick in at 30 something degrees. With a heat pump when it gets cold you have total electric heating.
 
Lineman were just here, changed out the meter, things looked way to nice compared to what am used to seeing in the neighborhood. Going out to get aditional info on name plate.

Water heater is in Garage and heated environment. House is 2 x 6 walls and about half mill (upper end). everything is nice to work on, and looking into all possibilties (house sitter leave a door/window open?)
 
Rockyd said:
The house is ran strictly on Heat pump, or if there's heat strip involved, it is well hidden, and without a manual switch.
Click to expand...


There is no manual switch to turn on the heat strips it automatic. A heat pump would be almost useless without the back-up heat strips because you wouldn't get any heat when it really gets cold.

He may be losing money by not programing his thermostat. It cheaper to let things get a little cool if there is no one home during the day. Even during the night there is a great deal of difference between a setting of 68 and 72. Setting for the lower temp, will save money.
 
Changed filter (was clean).

Heat pump is a Tempstar, Smart Comfort 2000

Mod#TCH 060AKD1

Maximum OCPD 60A
Minimum Circuit Cap 35.4

Comp 27.4 RLA and fan is 1/4 HP 1.5 FLA

Just seems like a lot of draw.
 
Rockyd said:
Changed filter (was clean).

Heat pump is a Tempstar, Smart Comfort 2000

Mod#TCH 060AKD1

Maximum OCPD 60A
Minimum Circuit Cap 35.4

Comp 27.4 RLA and fan is 1/4 HP 1.5 FLA

Just seems like a lot of draw.
Click to expand...


Sounds pretty poor compared to the units I see most often, haven't really seen a new 4ton that uses more than 35 amp max circuit and they run much lower.
 
Rockyd said:
Changed filter (was clean).

Heat pump is a Tempstar, Smart Comfort 2000

Mod#TCH 060AKD1

Maximum OCPD 60A
Minimum Circuit Cap 35.4

Comp 27.4 RLA and fan is 1/4 HP 1.5 FLA

Just seems like a lot of draw.
Click to expand...

Could it be that the colant is low and the unit is running more than it should. I would check that first.
 
Thanks Dennis, I never even considered that option. don't have the gauges or "tech know how" to get there, but have a friend that can. It maybe worse case scenario of "it what it is", but got to give it every reasonable attempt to offer up a solution that is palatable to the HO.

House is 2145 sq, ft. doesn't seem like to much for a medium size unit, but then if I knew that, I cold be an HVAC guy. Hard enough to be a good electrician.
 
I just tried to find information on the Tempstar 2000 and they are showing the 2000 to be an A/C unit. The 2400 is listed as a heat pump.

How old is this unit. They made some real beast a few years ago. With most of the new heat pump the compressor will only draw 30 Amp or less.

The heat strips on most units will vary from about 30 amps to 60 Amps. It will depend on the size of area to be heated. The blower motor doesn't take much power at all.

Did you check connections going to the blower where the heat strips are located. We tend to use a lot of cheap disconnects at this location ( sometimes provided by the HVAC guys ).
There can be up to 60 Amps of heat strips which tends to max out the rating of those cheap 60 amp disconnects. ( I have seen a couple melt). I'm talking about the plug in disconnect normally used for A/C units outside.
 
Rockyd said:
Changed filter (was clean).

Heat pump is a Tempstar, Smart Comfort 2000

Mod#TCH 060AKD1

Maximum OCPD 60A
Minimum Circuit Cap 35.4

Comp 27.4 RLA and fan is 1/4 HP 1.5 FLA

Just seems like a lot of draw.
Click to expand...

Didn't the OP say drawing 36-amps? RLA of 27.4 plus 1.5 fan is less than 30. 36 seems high. Did you check the voltage at the disconnect (or even better at the compressor relay)?

EDIT: an indication of low freon would be the outside unit icing up.
 
Alright, big return trip from an impossible attic... Thinking it might be a fan relay, because compressor runs forever, then after seemed like ten minutes, fan came on. Have my A/C tech friend come out in the morning (My tools are back in Alaska at PS4) cept for trusty clamp on amprobe.


Thanks all for all the great help and direction, am not an A/C guy on the average...
 
so far I do not believe we have a problem with the unit..that is a normal heat pump couple years out of the gate..It is a heat source I would not recommend..If someone can show me how a hermetic refrigeration unit with electric heater attachment is economical..feel Free to educate me other wise the math is correct and so is the electric bill..Here that unit is promoted by the utility company and you are suppose to receive a reduced rate on your electric bill..everyone I know are some what dissatisfied..the bills are high and so is the maintenance costs..
 
Your in MN. Here in Nevada (the snowbird capitol) winters are weak. For two months it trys to get below freezing at night, about 6 months of sweet weather, and 4 months of living in an oven (100+ daily). The town doesn't have gas. Some of the restaurants have exterior propane tanks, and don't know when natural gas will arrive UG.

So the heating gear isn't much, but the A/C is a big deal, so the whole area is big on heat pumps.

Taking a look at the unit later today (9:30).
 
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