Wiring an electric heater

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Old 02-17-11, 07:06 AM
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Wiring an electric heater

I have a heater that I want to connect to an existing 220v cable. The cable runs to an outlet but I will take the line out of the outlet and hard wire it to the heater. The heater has three connections: black, red and green(ground). The cable has four wires: red, black, bare copper (ground) and white. I asume the white wire will now hav no use and can be capped off. Is that right? Thanks so much.
 
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Old 02-17-11, 07:11 AM
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The guys on here are going to want to know more.....

What size is the wire in the cable ?

What amp breaker is on it ?

What are the spec's on the heater?

And they are going to tell you that it is 240 volts, and not 220 volts.
 
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Old 02-17-11, 07:20 AM
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Thanks,
The wire is 10 gauge.
The breaker is a 240 breaker, 30 amps
Correction duly noted.
John
 
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Old 02-17-11, 08:45 AM
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Yes, you would cap the white wire at both ends. However, there is one critical item missing here....how big is the heater? How many watts??
 
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Old 02-17-11, 09:21 AM
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Does this help:
Electric Unit Heater, Power Rating 5.6/7.5 KW, Heater Voltage 240/208 Volts, BtuH 25.6/19.1, Air Rise @ Outlet Degrees 37 Degrees Fahrenheit, Air Flow 650 CFM, Horizontal Air Throw 18 Feet, Maximum Current Rating 31.3/27.0 Amps, Phase Single/Three, Depth 8 1/2 Inches, Width 19 Inches, Maximum Mounting Horizontal Height 9 Inches, Height 21 3/4 Inches.
Set up for single phase.
 
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Old 02-17-11, 09:32 AM
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The wire is 10 gauge.
The breaker is a 240 breaker, 30 amps {heater speccs} ...240/208 Volts...Maximum Current Rating 31.3/27.0 Amps
The heater exceeds the capacity of your wiring and can not be used on it. You need #8 on a 40a breaker.
 
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Old 02-17-11, 09:46 AM
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That is a big heater....sounds like a large unit heater to me. They are almost always combination 1-3 phase and 7.5 is a popular size.....but yes that is too big for that wire and breaker. A 5KW would be OK, but that 7.5 will need updated wiring as ray mentioned.
 
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Old 02-17-11, 10:45 AM
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Thanks guys! It is a wall heater made by Dayton. The thing that confuses me is that the wattage is shown as 5.6/7.5. I am not sure what the range means. Could it be that single phase uses 5.6 and three phase uses 7.5? That probably does not even make sense but, before I rip out the wiring and change the breaker I want to make sure I understand. I appreciate your help.
 
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Old 02-17-11, 11:22 AM
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Big wall heater! I have seen some that actually looked like a furnace but were a large wall mounted unit, with options to heat room nearby. Anyway the difference in the heat rating is based on the VOLTAGE. At 240volts you would get 7500 watts. Ar 208V you get 5600. Most 3phase is 208V, all residential would be 230-240 volts single phase. Pull a new line of 8 guage and use a 40 amp breaker and you will be fine.
 
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Old 02-17-11, 12:05 PM
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That heater can be used in a 208V commercial three phase building or a 240V residential house. If connected to 208V, the output is 5.6kW (27A) or if connected to 240V the output is 7.5kW (31.3A). In either case however you would need to install a minimum of #8 copper wire for the hot conductors and use a 40A breaker or fuse. The ground wire can be #10.
 
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Old 02-17-11, 12:16 PM
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Thanks to all of you. You saved me a lot of time and $$$. I am going to pull a new #8 wire and install a 40 amp breaker. The last time i opened a panel was to put in a 120 line and as I recall I bought the wrong breaker (it would not fit in the box). The panel is squareD. Is there anything else I need to know when I buy the breaker other than the amperage?
 
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Old 02-17-11, 12:45 PM
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SqD makes two different panels, QO and Homeline. The panel cover should tell you what to use. Other than that I can't thing of anything else.
 
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Old 02-17-11, 12:52 PM
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Originally Posted by johndupuis View Post
You saved me a lot of time and $$$. I am going to pull a new #8 wire and install a 40 amp breaker.
By the way you only need 2 conductor (with ground) #8 for this heater rather than the more expensive #8/3g. As long as this is in a normal finished residential location the Romex NM-B cable should be okay, but if it's in an exposed area you may need some conduit or wall covering to protect the cable.
 
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Old 02-18-11, 02:30 PM
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I just wanted to let you guys know that I ran the new wire, installed the circuit breaker and hooked up the heater. It works like a charm! Of course, the weather soared up to 76 today; but I know it will get cold again. Thanks again.
John
 
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Old 02-18-11, 04:50 PM
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Good job. Thanks for letting us know how it worked out.
 
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