4500 sq.ft house requires what size panel?

[jimj]

May be a dumb and simple question to most, but I am obviously not an electrician. I bought this home without doing all of my homework. It was a spec. home, so did not have the prebuild time to make necessary adjustments and upgrades. So what size panel do I have.... 150 amp. Yup that is it. Compliments of Saussy-Burbank, eh ya.. premium builder my butt. Thank God I have 400 amp service to the house. I would like to add another 100amp, or 150amp, or 200amp, sub panel in a walk out unfinished basement. The current panel is in the garage and there is plenty of locations within 15 ft. of the current panel to a future sub panel in walkout basement.
Is this an easy install? Any idea of what I should expect to pay for labor and materials? I have heard anything from $500 to $2000. Suggest any specific questions I shoud,ask of the contractors?
Thanks for any and all help.
Jim
SC

 

[jwelectric]

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

Well brother Jim if I only install those items mandated by the NEC your house only needs 55 amps.

But 230 mandates that I install no less than a 100 amp service. Based on this with no more information than you have given I would say the electrician gave you one hell of a good job.

 

[benaround]

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

jimj,

You should contact some local EC for this type of info.

frank

 

[allenwayne]

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

Thank God I have 400 amp service to the house

Yup you said it right obviosly you are not an electrician.

 

[charlie tuna]

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

with your posted comments--you better keep quite and let the contractor ask the questions and also give you the answers!!!

 

[petersonra]

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

why do you think you have a 400A service if you have only a 150A panel?

I think that you need professional assistance in determining your actual needs here since you don't seem real clear as to what you have or what you need.

I can't imagine a 4500 SF house with only a 150A panel. The A/C alone is probably a big chunk of that already.

[ August 02, 2005, 09:34 AM: Message edited by: petersonra ]

 

[volt101]

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

I just put a 1200 amp service in a 36,000 sq ft home and "got away with it." Using this as a base and some simple math.
36000 / 4500 = 8 times
1200 / 8 = 150 amps.

Yep, must be the right size! Yep sounds simple..

Jim

 

[charlie b]

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

Come on, boys and girls. Let's be nice.

Originally posted by jimj: So what size panel do I have.... 150 amp. Yup that is it. . . . Suggest any specific questions I should ask of the contractors?

I don't know why you think a 150 amp panel is not adequate. But one thing you could ask for is a "service load calculation." That is the process that jwelectric alluded to, when he concluded that the NEC minimum load is 55 amps. Tell the contractor what you have, in terms of electrical equipment (range, water heater, washer, dryer, dishwasher, garbage disposal, air conditioner, heaters, etc.). Don't bother with any small plug-in appliance. The contractor should be able to calculate your "minimum required panel size" in five minutes.

Thank God I have 400 amp service to the house.

I can't even guess what makes you say that. The service to the house is provided by the utility, based upon their own rules of what size transformer and what size wires you need. As a rule, the size of the service will not be higher than the size of the main panel. So another question to ask the contractor is what size of service you do have. They can tell by looking at the meter and at the incoming wires.

I would like to add another 100amp, or 150amp, or 200amp, sub panel in a walk out unfinished basement. . . . Is this an easy install? Any idea of what I should expect to pay for labor and materials?

It can be done. Whether it is hard or easy will depend on too many things for us to list here. You really would have to invite a contractor over to have a look. You could even invite several to put in a bid. Only then will you get a reasonable answer. If you are uncertain of what questions to ask, or how to describe your desires in clear enough terms to allow the contractors to bid the job on an equal basis, you might consider hiring an engineer to write up a bid specification. This is usually overkill for a residential project, but it may give you greater confidence that you will get what you want and need.

 

[haskindm]

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

Jim,
To assume that a 150-amp panel is not adequate for your house is as wrong as some of the comments that you received here. Article 220 in the National Electric Code will determine the minimum service size required for a given installation. This will be determined by the square footage of the living space (which excludes garages and open porches) and the equipment that is installed. Most contractors try to size the service for some future expansion, but that is not required. If your calculated load is 149-amps, you could install a 150-amp panel and comply with the code. Also keep in mind that your 150-amp panel consists of two 150-amp phases. If your loads were all line to neutral (120-volt loads) you could get 300-amps out of a 150-amp panel without overloading. Nothing is a simple as it seems. Find someone to help you do a load calculation and you may find out that your service is more than adequate for your present needs. You may have to upgrade if you add significant loads in the future. I don't know what you mean when you say you have a 400-amp service available. Usually the power company will do a further de-rating of the load and run even smaller conductors to the house than the electrician runs from the meter to the service panel.
Don't jump to conclusions, a friendly discussion with the electrician that wired your house (not the general contractor who told the electrician "wire it to code" which really means don't do anything that is not required) may provide you with some answers and peace of mind.

 

[rick hart]

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

Man, you guys are a rough crowd or what?!?!?!

Charlie is right in suggesting we cut the home owner some slack. He's LOOKING for information here and not likely to PROVIDE any expetise to the forum later.

A question I have for the HO is- if he hasn't taken off like a scalded dog already- is:
What are any problems you are experiencing that make you believe your 150A service is undersized?

4500 sqft is a large house but even with all electric heat, I have seen 200A services provide adequate power to an all electric residence that size. To add the additional capacity costs a lot of money just for the equipment alone and it may never be needed as much as say.....granite counter tops...for the same base selling price.

 

[sceepe]

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

Assuming you have a heat pump HVAC system(s) with electric strip heat. The 240V / 1 phase load is approx 26 amps / ton

Assuming you live in the south, and assuming you have a house with normal insulation and normal glazing etc. You need approx 1 ton / 650 sqr ft. So thats about 7 tons of heat pumps for 4500 sqr ft.

Thats about 180amps at 240V 1 phase for the HVAC. Doesn't sound like 150 amps is enough. I would estimate that HVAC is about 70% of your load so I would want 260 amps capacity. Next size up panel is 400 amps. That should give you plenty of room to grow when the 4500 sqr ft gets too full.

However if you have gas / oil heat then your hvac load (and your elec service needs) will be a lot lower.

Bottom line is that without making a whole bunch of approximations and W.A.G.s (As I did above) No one can tell you what size panel you should have. If you can afford a 4500 sqr ft house you should be able to afford an engineer or good contractor to tell you if what you want to do can be done with a 150A panel. Hell if your not tripping breakers when the A/C starts up you may not even have a problem....

 

[jwelectric]

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

4500 @ 3 watts per sq.ft = 13500,
two small appliance and a laundry circuits = 4500
nothing else was given so this is all I have to work with.
13500 plus 4500 =18000 less 10,000 = 8000 times 40% = 3200 add the 10000 back and we have 13200 divided by 240 volts and

I see 55 amps.

230.79 (C) and I have a 100 amp panel. If there is more there I need to know what it is to do any better.

I could have 57kva of electric baseboard heat with thermostats and still come in with a 150 amp panel

 

[sceepe]

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

I see 55 amps.

And I see the absolute minimum required by code if you don't have any HVAC.

I could have 57kva of electric baseboard heat with thermostats and still come in with a 150 amp panel

WOW. lets see 57000/240 = 237 amps. You used 55 amps for lighting and small appliances, and your 150 amp main is good for 80% of 150 = 120 Amps. So you've got 120-55 = 65 amps left.

Well if you assume 65/237 =27% diversity you can make it work. Lets just hope that we don't get more than 27% of those baseboard heaters running at one time.... Nah, that'll never happen.

Who are we kidding? Everyone on this forum knows that a house this size usually has 200 - 400 Amp panel (at least when all appliances / HVAC are electric).

 

[jwelectric]

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

220.82 (C) (6) 40 percent of the nameplate rating(s) of electric space heating if four or more separately controlled units.

57,000 x 40% = 22800 divided by 240 = 95 amps plus the 55 = 150

the reason homes have 200 and larger services is because electricians don?t do calculations.

 

[rick hart]

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

Who are we kidding? Everyone on this forum knows that a house this size usually has 200 - 400 Amp panel (at least when all appliances / HVAC are electric).

Assuming 120/240 single phase? 120/208 not only lowers your kW but also raises your service capacity. I have installed quite a few 3 phase services on houses this size and yes- 200A is typically what goes in but, I won't get into the Optional Calculation Method.........

There is a reason that the inspector signed off on a 150A service and that reason may be that it is adequate and code compliant. The devil is in the details....which we don't have.

 

[jwelectric]

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

Just for the fun of it!

4500 square feet of living space with a 12kw range, dryer, 4.5 kw water heater, 1,2kw dishwasher, 1,2 kw microwave, .75kw disposal, 1.5kw whirlpool tub.

All this adds up to 44,150 va and do the minus 10 times 40% thing and we are left with 23,660 or 98 amps.

I went to page 718 of the NEC to pick the heat and AC for their 2000 sq. ft. house and doubled what they showed; this gave me 30kw heat and about 12 kw heat pump.

This will give me a total of 31,500 va for the heat and AC.

Add 31,500 to 23,660 = 55160 or 229.8 amps.

This would be about in line with a house in my area of that size.

I could get by with a 150 amp panel if it had gas heat and water heater.

 

[growler]

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

sceepe, you are absolutely right. This man needs a four hundred Amp. service. I think that it will cost a bit more than the 2K that he has in mind. He may even figure out why the builder was so cheap. But the first rule of business is " the customer is always right " ( if they have money to spend ). If he called me, I would not put a lot of effort into talking him out of spending his money. If he asked for a load calculation and advice, well, that's a different thing. I try to figure present and future loads. People now have some strange hobbies ( I have hooked up welders, kiln's , antique printing equipment , circuits for up to 30 pin ball games and probably pot growing equipment, he had a green house too). It takes a little effort to figure out what the real power requirements will be. The 150 or 200Amp may be just fine. I don't do a load calculation without a site visit because I have never had anyone tell me the whole truth ( they leave things out ).

 

[haskindm]

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% (so that the circuits would not be loaded to more than 80%). A 150-amp panel is suitable for 150-amps of non-continuous load. By the way, anything that is controlled by a thermostat is, by definition, a non-continuous load. This would include electric heat.

 

[rick hart]

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

I have a sort of personal experience with this sort of situation.

I used to live in a 4500 sqft house, all electric, 6 and a 2 ton AC and a 200A service built in the late 80's in North Texas. In the period of time I lived in the house the main never tripped. True, this is not a 150A service like the original post but still, no problem with electric heat.

I have to admit that I personally thought it was a little lightweight but I don't think looking back, that there was any danger. And I obviously did not think it was worth the expense to correct a problem that did not exist. But I also have to admit, I never put a pencil to it as far as a service calculation goes.

 

[jwelectric]

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

As I stated earlier most people don?t do load calculations and the main reason they don?t is because they don?t know how, just install a 200 amp panel and let it go. I have seen 900 sq, ft. apartments with 200 amp panels, and single wide mobile homes with a 200 amp service. I always ask myself if a true electrician installed this or was it a 200 amp and let it go type of installation

When confronted about the oversized panel their answer is, ?what if they want to add something later?? My answer to this is, ?I will charge them to upgrade their service to accommodate their load. What would you do if you were asked to add a load to a panel that was too small??

Most electricians use this ?future additions? to excuse their incompetence to do a load calculation. This has been the mentality for many years now. Just stick a 200 amp in there and let her go and if it is a big house stick a 320 continuous up and let her go..

This is evidenced by the following statement:

WOW. lets see 57000/240 = 237 amps. You used 55 amps for lighting and small appliances, and your 150 amp main is good for 80% of 150 = 120 Amps. So you've got 120-55 = 65 amps left.

Well if you assume 65/237 =27% diversity you can make it work. Lets just hope that we don't get more than 27% of those baseboard heaters running at one time.... Nah, that'll never happen.

220.82 0f the ?05 and 220.30 of the ?02 cycle of the NEC clearly states in part (C) under (6) that 40% of the total electric heat is to be used if there is more than four thermostats. A house this big would have at least five thermostats wouldn?t you think? And yes we are talking about baseboard heat.

This thought of sticking an oversized panel in is one reason electricians are starving today. The trade has become installing for the future and losing that work later on. I believe in giving the customer what they pay for and not one ounce more. Why would I set up a job for someone else in the future? Am I doing him a favor or am I stopping him from making more money?

The 150 amp panel in the original post must have complied with the code or it would not have passed. Now the home owner wants to install more equipment which will call for a service upgrade. He has come here to see how many ?ELECTRICIANS? will agree that the original service was installed to small and the ?ELECTRICIANS? of this forum are agreeing that the original service was installed to small although it passed.

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. This just doesn?t seem to make good business sense to me. If he was going to need it he should have paid for it at the start not talking us into derating a fellow electrician?s work.

I see this in unfinished basements. After the home owner moves in they want to finish the basement and most of the time with out permits. The electrician makes this possible by installing an oversized panel and knocks himself out of work. He gave work away for free.