Exceed digital thermostat wattage

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Old 01-30-08, 10:10 PM
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Exceed digital thermostat wattage

I've installed a programmable Honeywell thermostat (model RLV430A). On the manual it says it is rated at 3500W @ 240V. Right now I've got two baseboard heaters wired into this thermostat. One is at 1500W, the other at 2000W.

I'm thinking about replacing the 2000W baseboard heater since it is more than 20 years old. But the new ones they have at the local Home Depot (made by Cadet) for the same length (96"), are 2500W. This means if I were to change it, the wattage going to my thermostat would be at 4000W, 500W above what it is rated at. I'm not electrician. Could someone tell me if this is not advisable?
 
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Old 01-31-08, 12:47 PM
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It is not advisable. Exceeding the rated wattage will cause the thermostat to operate above its design temperature which could lead to premature failure or even melting components and so forth.

By increasing the wattage you could also overload the supply circuit which creates an unsafe situation. If the circuit is 20A, it should supply no more than 3850W of heaters; if the circuit is 30A, it should supply no more than 5760W of heaters. One heating circuit could supply a number of rooms, so look carefully.
 
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Old 01-31-08, 04:17 PM
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the biggest question is what is the voltage rating of the heaters? being a purely resisitve load this plays a big role in power. so if your using a lets say i.e. a 2000 watt rated heater rated at 300v, but you are applying 240 just because the heater says 2000w your wattage is not the same.
Originally Posted by nathanofseattle View Post
I've installed a programmable Honeywell thermostat (model RLV430A). On the manual it says it is rated at 3500W @ 240V. Right now I've got two baseboard heaters wired into this thermostat. One is at 1500W, the other at 2000W.

I'm thinking about replacing the 2000W baseboard heater since it is more than 20 years old. But the new ones they have at the local Home Depot (made by Cadet) for the same length (96"), are 2500W. This means if I were to change it, the wattage going to my thermostat would be at 4000W, 500W above what it is rated at. I'm not electrician. Could someone tell me if this is not advisable?
 
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Old 01-31-08, 04:31 PM
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Heater is 2000W @ 240V. Thermostat is rated up to 3500W @ 240V. The new heater that I could get is 2500W @ 240V + the existing one that is also going into the thermostat, 1500W @ 240V. This brings the load through the thermostat at 4000W @ 240V. I'm not electrician so I hope I'm making sense.
 
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Old 01-31-08, 06:39 PM
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thank you for clarifying that for me. some equipment is dual rated or maybe over or under rated. if it was a dual rated i.e. 120, 240 equipment you could use the lower voltage or if it was rated at a higher voltage it would be fine.thats why i asked. in your case its not.
Originally Posted by nathanofseattle View Post
Heater is 2000W @ 240V. Thermostat is rated up to 3500W @ 240V. The new heater that I could get is 2500W @ 240V + the existing one that is also going into the thermostat, 1500W @ 240V. This brings the load through the thermostat at 4000W @ 240V. I'm not electrician so I hope I'm making sense.
 
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Old 02-01-08, 12:38 PM
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Ok I now have one 1500W 240V and one 2000W 240V heater being controlled by my thermostat (RLV430A). Its rating is at 3500W @ 240V. I tried it last night and it heats up just fine. The thermostat does feel warm to touch but not hot. You can put your hand on it and be ok. Is this setup safe?
 
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Old 02-01-08, 12:55 PM
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Originally Posted by nathanofseattle View Post
Is this setup safe?
Depends on your definition of safe. Since you violated the manufacturer labeling by exceeding the rated current, it is not safe according to National Electric Code, Underwriters Labs or the product manufacturer.

Moreover, did you read my previous post about the load on the circuit? If this is a 20A circuit, you have exceeded the rating of the wiring in the walls also.
 
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Old 02-01-08, 01:01 PM
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How did I exceed the manufacturer's labeling by exceeding the rated current? I said in my last post that I'm using two baseboard heaters: 1500W and 2000W both at 240V. The thermostat is rated to 3500W 240V.

I'm guessing the circuit is 30A. On the circuit breaker it says 30 on the switch. Would that mean its 30A?
 
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Old 02-01-08, 01:15 PM
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That would

Your thermostat is gonna die alot quicker but theres nothing really unsafe going on ... Stupid yes but unsafe no
 
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Old 02-01-08, 01:31 PM
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It was my understanding that you had already replaced the 2000W with a 2500W heater. It is okay as it is currently installed with the 2kW heater.
 
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Old 02-01-08, 01:36 PM
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Thanks for your help. I'm basically running at the manufacturer's rated maximums for the wattage, 3500W.
 
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