load capacity

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Old 04-13-09, 09:33 AM
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load capacity

In considering the idea of installing some 240v baseboard heaters in an added-on section of the house, my first consideration is whether the current supply box is going to be adequate and can carry the added load. I realize this of course might depend on many factors and variations, but what might be one or two of the most basic things an electrician would be checking for to determine if the supply box would be fine or need an "upgrade?"
 
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Old 04-13-09, 09:49 AM
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An electrician would do a "demand load calculation". There are brief versions of this and long versions of this. If you search Google or look at any of several electrical how-to books you can find a procedure for doing it.

The biggest factors are square footage of the house, size of the electrical service (usually 60A, 100A, 150A or 200A), and major electrical appliances such as the range, hot water, central heating/cooling, spa, etc. If you post back with some of these details, we can help you with it.
 
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Old 04-13-09, 10:07 AM
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Originally Posted by ibpooks View Post
An electrician would do a "demand load calculation". There are brief versions of this and long versions of this. If you search Google or look at any of several electrical how-to books you can find a procedure for doing it. The biggest factors are square footage of the house, size of the electrical service (usually 60A, 100A, 150A or 200A), and major electrical appliances such as the range, hot water, central heating/cooling, spa, etc. If you post back with some of these details, we can help you with it.
Thanks, I'll be doing some Googling then, and probably post back with more details/questions. One question for now is how I might find out on my own the size of the electrical service I have now?
 
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Old 04-13-09, 11:57 AM
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Okay I Googled for info about how to tell what size electrical service I may have. I came up with this page among others: Global HR News: Home Electrical Service Size

So far I've come to the conclusion, after reading the info cited above, is that there'd be too much possibility of getting it wrong if I were to try to figure it out by myself. Looks like for me no choice other than having a qualified electrician ($$$) come look at it.
 
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Old 04-13-09, 12:05 PM
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No, finding your existing size isn't that hard...

Look at your main panel, and find the label that states its rating, and look at your main breaker(s). Thats a pretty good indication of what you have, assuming it was originally installed properly. Inspections on main panels are normally pretty thorough.

The website you posted was more about determining the REQUIRED service.
 
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Old 04-13-09, 12:26 PM
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If you have breakers, the amperage value is usually stamped on or near the main breaker handle.

If you have fuses the service is probably 60A or 100A and a physical description of the panel could lead us to the right answer.
 
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Old 04-13-09, 01:19 PM
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Here's a couple of pictures that might help to provide a physical description. I noticed the main breaker seems to have no indication what size it is (although the round yellow sticker says 22,000 AIR), and on the panel label sticker on the panel door the "mains rating" space is blank with no info stamped or amps otherwise indicated.

http://i207.photobucket.com/albums/b...1/IMG_1070.jpg
http://i207.photobucket.com/albums/b...1/IMG_1071.jpg
 
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Old 04-13-09, 01:32 PM
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Can't quite make it out, but looks like the main breaker is 100?

Do you have electric appliances? I see the breakers for them, but my house was wired/plumbed for both gas and electric.
 
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Old 04-13-09, 01:41 PM
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Originally Posted by Gunguy45 View Post
Can't quite make it out, but looks like the main breaker is 100? Do you have electric appliances? I see the breakers for them, but my house was wired/plumbed for both gas and electric.
It doesnt say anything on the main breaker that I can see. Only thing there is the round yellow sticker, nothing else around the main breaker labeled. Yes got electric appliances and no gas. Have electric water heater, kitchen stove, clothes washer/dryer, refrigerator. (Existing heat source is oil-fired Toyostove)
 
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Old 04-13-09, 01:46 PM
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Originally Posted by Gunguy45 View Post
The website you posted was more about determining the REQUIRED service.
Gunguy it seems to me the web page I posted talks rather extensively about how to determine the size of the existing service, moreso than determining the required service. Also, on something like this I think I need to be sure without assumptions on whether it was ever installed properly, inspected thoroughly, or any other "pretty good indications" otherwise. The last four or five paragraphs of the web page there seem to indicate there can be quite a margin for error on the part of an inexperienced person trying to figure it out for himself, even with step-by-step instructions to do so. Nothings ever simple, always complicated
 
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Old 04-13-09, 01:46 PM
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Embossed into the plastic on the end of the handle? Not all breakers have nice white letters....
 
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Old 04-13-09, 01:55 PM
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Originally Posted by Gunguy45 View Post
Embossed into the plastic on the end of the handle? Not all breakers have nice white letters....
Okay okay. 100A is embossed into the plastic on the end of the handle, in black letters hard for me to see!

So I'll suppose based on that we'll just automatically assume it's a 100A service? Thanks....
 
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Old 04-13-09, 01:56 PM
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True about the site...I didn't read all the way through. Other than the actual service conductor size though...everything else is pretty easy to determine. Meter, conduit, panel and main breaker can all be measured/looked at. The Pro's can probably tell you about the panel just from looking at it.

You can also look at the age of the house to help determine if an upgrade was probably done. Example...A house from the 50's with 200 amp service has probably been upgraded sometime in the past. You can also go to the permitting office and look for any permits that were pulled (pretty sure of this anyway) indicating whether electrical was ever upgraded or added to.
 
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Old 04-13-09, 02:13 PM
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So let's assume for the sake of assumption that it turns out to be a 100A electrical service. With the electrical appliances I mentioned plus a few other typical electrical devices of course like toaster, lighting, computer, tv, etc. in small house, will this electrical service probably not be able to handle maybe three additional 240v baseboard heating units, one two-footer, one three-footer, and one four-footer? Or still too hard to say? My guess is that the service would have to be upgraded. How much does that cost and how involved is that (when an electrician does it, of course)? He's coming out later $$$ today. Any guesses what he'll say in regard to whether it would need an upgrade? C'mon, guess. It'll be fun.
 
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Old 04-13-09, 02:21 PM
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I really doubt you'd need a service upgrade for it to function...but it sure wouldn't hurt.

You have room, I think..(could be wrong..no Pro) for a couple of 240 breakers. Though some panels they can only be installed in certain spots...as I said, no Pro. The breakers would protect those circuits.

Might need to be aware to not run all burners and oven on the range while drying clothes at the same time.

If you need a service upgrade, I'd guess $1500 for that (though I don't know where you are, higher in a Metro area). Running the 240 circuits for the heaters and installing them..all parts included..maybe $1000? Completely WAG.....

Good Luck!
 
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Old 04-13-09, 02:38 PM
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Originally Posted by Gunguy45 View Post
I really doubt you'd need a service upgrade. Completely WAG.....
Okay, we'll see. Glad to hear you think so far there's a good chance I may not need to upgrade.

Yeah if it isn't already, it will likely be completely WAG like you said.
Tell me though, I must know, what is WAG?
 
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Old 04-13-09, 02:40 PM
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It's definitely a 100A service. I think you're just fine to add a few baseboard heaters. If we were talking a spa, I'd say upgrade, but the heaters are no problem.

What is a problem however is that 50A double-pole breaker in the slots labeled dryer. That breaker should be 30A if it serves the dryer, or correctly labeled if it serves something else. The water heater should also be a 30A (which I think it is) but can't quite read the breaker handle.
 
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Old 04-13-09, 02:52 PM
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Originally Posted by ibpooks View Post
What is a problem however is that 50A double-pole breaker in the slots labeled dryer. That breaker should be 30A if it serves the dryer, or correctly labeled if it serves something else. The water heater should also be a 30A (which I think it is) but can't quite read the breaker handle.
There are two 50A double-pole breakers, the one on the top right is for the range, the one below it serves the dryer. The water heater one is a 30A.

How come the dryer breaker should be 30A? Thanks.
 
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Old 04-13-09, 04:01 PM
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I guess no one as ever seen a dryer that draws/requires 50A breaker. Most are 30. You'd need to check your nameplate.

btw WAG is Wild A$$ed Guess
 
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Old 04-13-09, 04:35 PM
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Originally Posted by Gunguy45 View Post
I guess no one as ever seen a dryer that draws/requires 50A breaker.
Now, is that an EG (educated guess), or is that a WAG too?
 
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Old 04-13-09, 04:43 PM
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That was an EG by Gunguy45. A problem with a 50a breaker for the dryer is if it is wired with #10 as is standard for dryers. If you have a #10 on a 50a breaker that is a fire hazard.
 
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Old 04-13-09, 04:53 PM
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Originally Posted by ray2047 View Post
That was an EG by Gunguy45. A problem with a 50a breaker for the dryer is if it is wired with #10 as is standard for dryers. If you have a #10 on a 50a breaker that is a fire hazard.
Thank you ray for that info. I'd better make sure to get that problem corrected then. And thanks Gunguy and ibpooks for all the input here too.
 
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Old 04-13-09, 05:23 PM
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Most of my edumacation was from just trying it to see if it worked... Oh and to all the great experts on here.
 
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