4-Ton A/C Amperage

Hi,
I am replacing a 2.5-ton central a/c with a 4-5 ton unit. A potential installer says I need 300-amp service but it looks like I have only 200-amp service according to my utilty company. The original unit is truly undersized, so please, no screeds about more insulation, caulking, weatherstripping, attic fans, ad nauseum. Been there, done that. Do we really need this kind of amperage?
TIA, James
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Can't see it from here but I'd have to say probably.........NOT!!
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No way...not for a measly 4 tons. More like 30 amps at most....
candice
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CLSSM00X7 wrote:

I think the installer meant the total amperage my electric company supplies to the house. From other posts it appears that 200 amps are sufficient even with an all-electric home.
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Do you have enough service to heat your house with electric furnace, or baseboards? If so.... then you have plenty of electric to run an AC.
I doubt you will run your baseboard heat and the AC at the same time. So the panelbox oughta be OK.
Stove runs about 50 amps, full blast. Which you'd only do if you were cooking for a family reunion. And if you had the stove full blast, you'd likely turn off the baseboards. Still enough juice.
Teenager with a stereo and a hair dryer. Now you need a 500 amp service. Hair dryer only, about 400 amp service. (very big grin here)
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This is Turtle.
If only a 5 ton will cool it. Your not really looking at a 300 amp service for any 200 amp service will work fine. You have i guess All electric straight electric heat , stove , hot water tank, driers, and lites everywhere. Your still looking at 200 amp service. Does this fellow install meter pans and electric service to houses too?
Now if you want to add another 5 ton and another system to it for new added area , you might look at 300 amp service.
TURTLE
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I am talking about replacing the inside (condensor) portion of the unit to match the outside (compressor) unit (please don't ask why this mismatch occured). The installer was making noises about bigger wiring and amperage needed for the condensor unit, which is the 2.5 ton part of the a/c, hence my post.
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On Thu, 24 Jul 2003 03:13:18 GMT, snipped-for-privacy@nowhere.com.invalid (James Harvey) wrote (with possible editing):

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volts500 wrote:

My bad on the misnamed parts. My mind went blank when I was typing :). The house has 1825 sq ft, electric stove, oven, heating, a window a/c unit (which will be removed if we get adequate cooling), garage door opener, 2 ceiling fans, 3 tvs, stereo system. The house has 3 bedrooms, 2 full baths. What other info do you need?
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volts500 wrote:

James Harvey wrote:

Thank you. What kind of heating? Gas? Electric baseboard? Electric heat strip in the AHU? What is the total wattage of the electric heat (if it's even electric). No dishwasher? Disposal? Hot tub? (or anticipation of such in the future?) No table saws or other power equipment? Is the water heater electric.....if so what is the wattage? Does the 1825 sq. ft. include the garage........if so what is the approx. sq. ft. of the garage? No freezer? Electric dryer?
What is the wattage of the oven (you should see a nameplate when you open the oven door.)
It's still not clear what's being replaced......I don't understand how you can upgrade from a 2.5 ton unit to a 4 or 5 ton unit without replacing the existing (outside) condensing unit.
Either way, for the equipment that will be in place when all is done, we need to know what the "minimum circuit ampacity" is (stamped on the condensing unit nameplate) for the (outside) condensing unit and the kW of the (inside) AHU (stamped on the nameplate.)
Sorry about all the questions, can't see it, can't guess. Please verify that you have a 200 amp service. Can you see anywhere on the electric service panel what the rating is? Usually (but not always) the main breaker will have a "200" stamped on it. If you have a 200 amp service, the incoming wires, including insulation, will be at least 1/2 inch (or larger) in diameter if copper, larger if aluminum.
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We do have 200 amp service. Electric heating strip in the AHU (prolly around 7 kW - nameplate covers many heating configs - 3 to 11 kW)). Electric dishwasher, clothes washer, dryer, disposal, small aboveground pool pump, water heater (about 5000 kwH/yr), 25 amp MCA on the condensor, refrig/freezer. I'm guessing around 9 kW on the oven. I don't understand all these 120/240 V ratings. I have a circular saw among other lower power tools. The garage is about 400 sq ft. in addition to the house.
Whew.
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James Harvey also wrote:

Here's the service demand load calculation:
1825 sq. ft. @ 3 VA (garage not to be counted) 5475 VA 2-20amp small appliance @ 1500VA ea. 3000 VA Laundry 1500 VA Range (used 12 kW instead of 9kW) 12,000 VA Water heater (5 kW) 5000 VA dishwasher (assumed 1.2 kW) 1200 VA dryer 5000 VA disposal (assumed 3/4 hp) 1700 VA pool pump (assumed 1 hp) x 125% 2400 VA garage door opener (assumed 3/4 hp) 1700 VA ----- ---------- Subtotal general load: 38,975 VA
First 10kVA at 100% : 10,000 VA Remainder of general load at 40% : 11,590 VA (28,975 VA x .4) ----- ---------- Total net general load: 21,590 VA
Assuming a heat pump (approx. 4 to 5 ton) with an MCA of 40 amps. and a supplementary heat strip of 11kW (worst case scenario) 40amps x 240 volts = 9600 VA + 11,000 = 20,600 VA (at ----------------
Total: 42,190 VA
42,190 VA / 240 volts = 176 amps total demand
So........the installer did have a legitimate concern about the service not being adequate, but as you can see, a 200 amp service is sufficient though.
As far as the size wire feeding the AHU, you'll need to check the nameplate on the unit to be sure, but it looks like a #6 copper (for the full 11kw plus the fan motor). Of course the wire feeding the 4 or 5 ton CU (if no more than the assumed MCA of 40 amps) needs to be at least a #8 copper.
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volts500 wrote:

Thanks! That was very informative :).
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I have a 42000 (3 1/2 tons) BTU AC unit with 100Amp service for 2400 square feet. No electric heat, however, you won't be heating with the AC on anyway. I have lots of electrical equipment including electric dryer, electric oven (gas cooktop), all kinds of power tools, computers, and TVs. I have never had a problem, so with 200 Amps, all should be ok.
James Harvey wrote:

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snipped-for-privacy@nowhere.com.invalid (James Harvey) wrote in message

If you mean PANEL RATING, 200A is plenty even if you have a large house with an electric dryer and stove. If you mean the circuit wired to the compresser is only <20> amps you are probably out of luck.
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If I'm not too far off the mark, four tons oughta take 10 gage wire, and a double 30 breaker. So, the 300 amp service sounds like overkill.
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