Upgrade from 100amp to 200amp


Old 06-25-02, 05:13 PM
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Location: Michigan
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Exclamation Upgrade from 100amp to 200amp

This is a rather detailed question so be patient with me. I am getting ready to upgrade my service from 100amp to 200amp. The main reason is I am adding a central air conditioner and I have no more room in my box for a double breaker. Now, I am assuming that I have to upgrade to add the air conditioner. I am not sure what the total load on the house is. I have a 100amp main breaker, a 15 and a 30amp double, and a variety (qty of 16) of 15 and 20 amp singles.

First of all, does this sound normal? Secondly, is there a chance I can double up a couple of my smaller circuits (i.e. bedrooms, laundry room, etc.) into one to make space for a double in my box? I have an electric dryer, a gas range, a gas water heater, and an electric well pump. These are my main appliances.

How would I go about finding out what my total current load on the house is and also does anyone know what kind of amperage a 2 ton (10 SEER) Janitrol air conditioning unit would pull?

Any help would be greatly appreciated!!

Thank you so much!!
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Old 06-25-02, 05:47 PM
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There are two pretty-good ways to free up space in your panel, but the way you suggested is not one of them:[list=1][*]Replace some of your 15 and 20 amp single-pole breakers with tandem or twin breakers. Just make sure you don't move part of a multiwire circuit.[*]Install a subpanel.[/list=1]To determine if you really need the 200-amp service, you need to do a "demand load" calculation. Almost any good electrician can do it for you, or you can look here for Wg's explanation of how to do it.
Old 06-25-02, 05:48 PM
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You do not nesasarily have to upgrade to a 200A service to accomodate an A/C installation, but you might. You need to perform a demand calculation for your house. If it shows a load in excess of 100A, then you will need to upgrade. If less than 100A, then you would need either a sub panel to accomodate additional circuit breaker positions, or research whether your existing panel can use the 1/2 height (space saver) cirucit breakers and make space that way. Below is two links to calculations for residential demand.
Old 06-25-02, 08:02 PM
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Your 2 ton Seer 10 a/c unit will approx. 15 amps. Plan on a 20 amp circuit. The Manufactuers spec sheet will have listed the full load amps and the minium circuit ampacity.
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