4500 sq.ft house requires what size panel?

[jmd445]

Re: 4500 sq.ft house requires what size panel?

Sceepe, PLEASE do not use statements like "Assuming you have a heat pump HVAC system(s) with electric strip heat. The 240V / 1 phase load is approx 26 amps / ton"

Please do the math. I have a 3-ton unit at home and it draws 9 amps @240V. You may be thinking about the start-up in-rush, or maybe a bank of toasters in the air handler. Using your logic a window airconditioner could never be plugged in.

 

[sceepe]

Re: 4500 sq.ft house requires what size panel?

sceepe,
Why did you only use 80% of the capacity of a 150-amp panel. In a residential occupancy there are usually no continuous loads, and if there were, only that portion of the load that was continuous would need to be figured at 125%

Just a factor of safety I have grown use to using because I distrust diversity factors. You're right, not required.

I believe in giving the customer what they pay for and not one ounce more.

Your making my point for me. Mr. Homeowner got the absolute minimum. The load calcs in the NEC are not used to determine the optimum service size. They are used to determine the MINIMUM service size. I wouldn't want the smallest possible, garage, sewer line, hvac, or service entrance. I'm sure you would not either.

the ?ELECTRICIANS? of this forum are agreeing that the original service was installed to small although it passed.

I am not an electrician. This forum is not just for electricians. I did not mean to give the impression that I thought the original install was in error. Just a poor design

What I see is a home owner that wants something for free per say a larger service. What I am hearing is that it should have been GIVEN to him from the start.

The electrician makes this possible by installing an oversized panel and knocks himself out of work. He gave work away for free.

No one is saying it should have been given to him. The value of the larger service should be reflected in the price of the house. The electrician should make more to install a larger service. Granted you would make a lot more if you could install the bare minimum, rip it out and install a larger one later on.

However, the homeowner admitted he did not do his homework. He thought he was getting a house with bunch of extras and turns out he got the bare minimum electrical service. Its like buying a Ferrari with a volkswagon engine. Would you be arguing that he should bring in the car for a bigger engine if he needed to go over 55 mph.

Maybe we see thing differently. I believe in maximizing customer satisfaction instead of profit? In my experience, it proves more profitable in the long term

 

[jwelectric]

Re: 4500 sq.ft house requires what size panel?

When in the real world of residential contracting there is no room for maximizing. I see this maximizing as a sure way to lose a bid. The electrical contractor that installed this 150 amp panel got this job because he knew how to calculate the load and come in with a low bid.

I do understand that doing commercial and industrial work is a lot different. Most of these jobs are designed by some engineer that throws a load factor that will insure that they are large enough to cover their behinds. We can see this in the way that you calculated the heat load for this house. Every electrical contractor that bids on that job is bidding on the same set of specs, it is a level playing field,

Do you see a difference there? I bid it as tight as a banjo string and as minimum as possible when I bid a house. Why? It is the only way to get the work. Just as the electricians that bid on the over specked commercial jobs, low man gets the job.
Residential has become a dog eat dog world. A few contractors have a builder that they do work for all the time but this is dying out fast.

 

[sceepe]

Re: 4500 sq.ft house requires what size panel?

Please do the math. I have a 3-ton unit at home and it draws 9 amps @240V. You may be thinking about the start-up in-rush, or maybe a bank of toasters in the air handler.

I did the math before making the statement. MCA on a 3 ton trane air handler #TWE031E13B with 10 KW strip heat is 50Amps at 240 1 phase. Coupled with a 3 ton trane condensing unit with an MCA of 21Amps at 240 1 phase. Thats 71amps / 3 tons = 24 amps / ton. Do the same for all splits from 1 to 5 tons you'll find they average about 26 amps / ton. Again, thats for splits with strip heat (AKA a bank of toasters).

Using your logic a window airconditioner could never be plugged in.

I would not recommend plugging in a 3 ton window unit with strip heaters.

 

[stud696981]

Re: 4500 sq.ft house requires what size panel?

I have to agree with jwelectric. A lot of people don't realize that when it comes to residential work, the GC wants the CHEAPEST possible price for the job. This in turn means wire to plans and NEC....bare bones, no extras!

Now if the house is a custom built job, the HO can tell the GC want they want and pay extra for additional stuff. In the real world, most custom jobs I have been on the HO only pays for the minimum job when it comes to electrical. They are more conserned about carpeting, kitchen cabinets, etc.

 

[jwelectric]

Re: 4500 sq.ft house requires what size panel?

Originally posted by sceepe:
I did the math before making the statement. MCA on a 3 ton trane air handler #TWE031E13B with 10 KW strip heat is 50Amps at 240 1 phase. Coupled with a 3 ton trane condensing unit with an MCA of 21Amps at 240 1 phase. Thats 71amps / 3 tons = 24 amps / ton. Do the same for all splits from 1 to 5 tons you'll find they average about 26 amps / ton. Again, thats for splits with strip heat (AKA a bank of toasters).

220.82 (C) Heating and Air-Conditioning Load. The largest of the following six selections (load in kVA) shall be included:
(4) 100 percent of the nameplate rating(s) of the heat pump compressor and 65 percent of the supplemental electric heating for central electric space heating systems. If the heat pump compressor is prevented from operating at the same time as the supplementary heat, it does not need to be added to the supplementary heat for the total central space heating load.

Here is a prime example of some one not knowing how to do a load calculation. I have posted twice in this thread how to calculate the air handler and heat pump compressor and you still do it wrong.

Using your numbers that are high for a heat pump (must be an 8 seer) from way back

24 amps times 240 volts = 5760 va
10,000 times 65% = 6500 plus the 5760 for the heat pump = 12,260 divided by 240 volts = 51 amps
51 amps is what would be used for the demand on the service for 10kw heat with a 3 ton Trane not the 71 amps you came up with.

To pad a service at the rate of 40% is just unheard of in the residential trade. Yes we all know that most PEs do this but I have never figured out why.


edited to get my quote codes right

[ August 03, 2005, 05:32 PM: Message edited by: jwelectric ]

 

[jimwalker]

Re: 4500 sq.ft house requires what size panel?

It costs very little more for 200 amp back to back and makes a great selling tool for you to the GC and the GC to the customer.When that customer sees your sticker on his panel and wants to add a pool or hot tub he will call you.Do you want to tell him his 3 month old home cant support it ?

 

[benaround]

Re: 4500 sq.ft house requires what size panel?

Charlie,

Good thing you didn't tell him to ask the EC!

frank

 

[allenwayne]

Re: 4500 sq.ft house requires what size panel?

Thank God I have 400 amp service to the house

Did anyone see this part of the post ??????
How do you have a 150 panel and a 400 amp service .
but what is the main size 400 or 150 or 200 .....

 

[sceepe]

Re: 4500 sq.ft house requires what size panel?

One last quote and I will give up.

If the heat pump compressor is prevented from operating at the same time as the supplementary heat, it does not need to be added to the supplementary heat for the total central space heating load.

When unit goes into defrost both the heat strips and the compressor are running at the same time. Heat pumps used in cold weather frequently ice up and must go into defrost. If unit does not have strip heat it puts out cold air during the defrost cycle. In my opinion, this means the compressor is not prevented from operating at the same time as the supplemental heat so you must add the loads.

as for the rest of this thread, I need to admit I am out of my comfort zone. I don't due residential work and I have no doubt it is as cut throat as you guys say it is. If owner / GC doesn't care about the value added in having a panel with extra capacity and your are not going to get paid for it then I agree why do it. I don't give away my services why should you.

 

[jwelectric]

Re: 4500 sq.ft house requires what size panel?

Originally posted by jimwalker:
It costs very little more for 200 amp back to back and makes a great selling tool for you to the GC and the GC to the customer.When that customer sees your sticker on his panel and wants to add a pool or hot tub he will call you.Do you want to tell him his 3 month old home cant support it ?

I am sure that the average home owner knows about load calculations. I have said many times those statements like this are why electricians can?t make money.

I would be proud to tell the home owner three months later that he will need a service upgrade in order to add a pool or hot tub. If he decides to get some one else to install it then I helped my fellow electrician make a living.

Should he decide to let me do the work I would offer a discount on my price and explain to him how smart I am about the code unlike those who avoid doing a calculation. I tell him that if the electrician was too lazy or not smart enough to do the calculation wonder what else is done wrong with his home.

I like pulling out my code book and doing a calculation for their water heater and then showing the home owner how dumb the electrician was that installed a 30 amp breaker when the load calls for a 25 amp breaker. This always gets them thinking.

 

[haskindm]

Re: 4500 sq.ft house requires what size panel?

Where do you buy the 25-amp wire to put on that 25-amp breaker? Overcurrent devices are installed primarily to protect CONDUCTORS, so since we need to install a 30-amp conductor, why not install a 30-amp breaker? Especially since they are the same price and more readily available.

 

[jwelectric]

Re: 4500 sq.ft house requires what size panel?

Originally posted by haskindm:
Where do you buy the 25-amp wire to put on that 25-amp breaker? Overcurrent devices are installed primarily to protect CONDUCTORS, so since we need to install a 30-amp conductor, why not install a 30-amp breaker? Especially since they are the same price and more readily available.

I need some help understanding you statement here.

What you are saying is that if I install a #6 NM conductor for a water heater I can use a 50 amp breaker.

I don?t think so! I think that if I read the code I will find that a 25 amp breaker is what is called for.

-2005 422.13 Storage-Type Water Heaters.
A fixed storage-type water heater that has a capacity of 450 L (120 gal) or less shall be considered a continuous load.

-2002 422.13 Storage-Type Water Heaters.
A branch circuit supplying a fixed storage-type water heater that has a capacity of 450 L (120 gal) or less shall have a rating not less than 125 percent of the nameplate rating of the water heater.

4500 times 125% = 5625, 5625 divided by 240 = 23.4

-240.4 (B) Devices Rated 800 Amperes or Less. The next higher standard overcurrent device rating --------- shall be permitted to be used,

Increase to a 25 amp breaker.

422.10 clearly tells us that we are to use the marked rating of the appliance to size the circuit that feeds the appliance.

-422.10 (A) Individual Circuits. The rating of an individual branch circuit shall not be less than the marked rating of the appliance

Where the thirty amp breaker comes into play comes from 422.11 (E). It is the thinking that it is a #10 stick a 30amp on it and be done that degrades our trade.

 

[charlie b]

Re: 4500 sq.ft house requires what size panel?

Well, this discussion has gone on for a while, with some interesting points being made. But the homeowner who started this ball rolling has yet to let us know if we are being of any help, or if he has made a decision on what to do with his service.

Shall we call this one done, and close the thread?

 

[jwelectric]

Re: 4500 sq.ft house requires what size panel?

my vote is yes

 

[haskindm]

Re: 4500 sq.ft house requires what size panel?

In the case of a water heater, the overcurrent device is installed to protect the CONDUCTORS not the appliance. See 422.11A tells us that the overcurrent protection must comply with 240.4. 240.4 deals with the protection of conductors. IF a maximum protective device ampacity is marked on the appliance then we need to protect the appliance with an overcurrent device that does not exceed that rating. I have never seen a water heater that said "Maximum Overcurrent device 25-amps". Since there is no restriction such as that, then we need only protect the conductor. 422.13 simply instructs that the water heater is treated as a continuous load. This means that we will need a conductor with an amapcity of at least 23-amps, instead of the 19-amps that we would normally figure for a 4500-watt load. Since we both agree that a minimum #10 conductor is to be installed, and 240.4(D) instructs us to protect #10 CU conductors at 30-amps, there is no reason to install a 25-amp breaker on this circuit. Remember that 422.11 is that article that deals with overcurrent protection for appliances, not 422.13.

 

[charlie b]

Re: 4500 sq.ft house requires what size panel?

Originally posted by haskindm: . . . 240.4(D) instructs us to protect #10 CU conductors at 30-amps, there is no reason to install a 25-amp breaker on this circuit.

Not quite. 240.4(D) instructs us to protect #10 CU conductors with nothing higher than 30 amps. A 25 amp would suffice for this application, and a 30 amp would also meet code.

First Person: "I contend that the grass is green."
Second Person: "No you are wrong. Clearly, the sky is blue."

It is time to end this one. The OP appears to have no more interest.