Small (30A/240) service ok?

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Old 09-09-08, 10:17 PM
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Small (30A/240) service ok?

The house/cottage is so small/old, the electrician took one look at it and said not to bother upgrading the service - but this after years of hearing all about how illegal/ immoral/insafe/ insane it was! Naturally i have a different view of it. Anyway, he recommended new panel only to replace the old fusebox. Loadwise there's the usual furnace, fridge, sump pump, and a 1200watt water heater, assortment of lights, TV, stereo, & computer. Stove is gas. One person occupancy (usually). No space for laundry or dishwasher or anything other than a few little things like hair dryer, kettle.

How much does someone really need? What would a bachelor apartment, mobile home or other comparable use? Another way to go at it is to wonder what can reasonably be added - window a/c, spot heater, dehumidifier, etc. ? What i'm looking for here is not a load calc which i guess i can do, but just examples or ideas you know about to reassure me (or not).

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Old 09-09-08, 10:46 PM
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When you say 30A you are talking about the box itself. Do you have any idea the capacity of the service coming in? For 30A it could be #10 but that seems awfully small. How long is the service run to the street or transformer? Do you currently have issues with dimming of lights with loading, like turning on a hair dryer on high?

The cost of a new panel is minimal. I would put a 100A in BUT the service entrance has to be able to handle it and that is where you get into more money. You could need a new meter box, etc. Is it still the old meter from 60 years ago? Also depending on how long the run is on your property, you may be responsible for some of that also. Usually the utility is only responsible for the run to your house or the first pole on your property.

Where is your little cabin located?
 
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Old 09-09-08, 11:23 PM
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I personally would not risk adding "anything" to these few circuits. Certainly not a window A/C. It is ideal to not exceed 80% of the maximum capacity of the circuit/service. In your case that would be 24 amps total. (if indeed you have a 30 amp service that is). Your main breaker may not be tripping, but wires and C/B ers can get dangerously warm and over time "poof" and you have a fire. If you access to an ampmeter you could see how close you come to 30 amps when normal loads are in use.
 
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Old 09-10-08, 05:49 AM
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The smallest service the NEC will allow to be installed for a house is 100 amps.
 
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Old 09-10-08, 08:34 AM
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It sounds like 30A service is a bit undersized for the named loads, but if you're not tripping breakers or blowing fuses you're not overloading it.

To refine pcboss' statement a little further, the minimum service for a dwelling is 100A. Recreational cabins and so forth may not necessarily meet the definition of a dwelling. Mobile homes count as dwellings, most apartments count as dwellings.

A single unit, providing complete and independent living facilities for one or more persons, including permanent provisions for living, sleeping, cooking, and sanitation.

This interpretation would be up to your local building department or power company policies.
 
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Old 09-10-08, 03:35 PM
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THanks all.

Can I assume a furnace is 8A, fridge 5A, dozen lights/tv/computer 10A, which added to 12A water heater is 35A total??
Plugging in one electric heater or one a/c takes it up to 45 to 50A which is within the 60A that this "30A" service actually provides if i understand correctly. Its a bit tight -but doable?

I don't know what size wire the service line is but its not far to the street - about 30ft.

This would be considered a permanant dwelling.

Not sure what a service entrance is but the electrician said he would move the meter to install the panel.

thanks for any further thoughts
 
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Old 09-11-08, 07:44 AM
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Originally Posted by canbyte View Post
Can I assume a furnace is 8A, fridge 5A, dozen lights/tv/computer 10A, which added to 12A water heater is 35A total??
Those are reasonable numbers for one person occupancy. It's certainly not an official load calculation by the schedule.

Plugging in one electric heater or one a/c takes it up to 45 to 50A which is within the 60A that this "30A" service actually provides if i understand correctly. Its a bit tight -but doable?
You usually count the larger of the A/C or heat, but not both as they do not run at the same time. The thing you cannot guarantee is that the loads are balanced across both legs of the service, so you could trip the main with only 35A if it was all on one side.

This would be considered a permanant dwelling.
Then any new service would have to be 100A minimum. It's unclear if replacing the main panel is considered enough of a change to mandate a full upgrade. In my area, moving the meter is a large enough change to require compliance with new service requirements.

Not sure what a service entrance is but the electrician said he would move the meter to install the panel.
Service entrance generally means all of the wires and equipment which connect your house to the power company. "Service drop" is the wire from the pole to the house, weatherhead, conduit mast/riser, meter base, down to the main breaker and/or panel is the service entrance.
 
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