4000 watt htr.

[jes25]

I am going to hook up a 4000 watt 240v heater. FLA is 16.7A. I plan to use #10 cop. on a 30A brkr. I will not have a disconnect seperate from the marked on/off on htr. The unit is T-stat controlled. I have not done to many of these, does anyone see a possible problem?.....Thanks

 

[George Stolz]

Re: 4000 watt htr.

Check the "Max. Overcurrent Protection" of the unit. It's probably 20 amps, and if the heater has a problem, you could be liable for having a 30 amp OCPD instead of a 20.

The heater has a disconnect already installed? Cool.

But that's all I see.

Edited to nip a stupid comment in the bud.

[ January 05, 2005, 09:06 AM: Message edited by: georgestolz ]

 

[guesseral]

Re: 4000 watt htr.

Make sure the heater dis/therm is 2 pole. In order to be used as the disconnecting means it must break both legs and say OFF. Sometimes a single pole therm is used and only breake one leg.

 

[charlie b]

Re: 4000 watt htr.

An on/off switch on the heater itself would not qualify as the disconnecting means required by 424.19, unless you also meet one of the requirements in 424.19(C)(1) through (4).

A thermostat would not qualify as a disconnecting means, unless there is a way to disable both legs (guesseral has pointed out), and unless it disables both legs on a permanent basis. See 424.20. There must be an ?off? position as part of the thermostat.

 

[guesseral]

Re: 4000 watt htr.

Thanks Charlie. Ran into this before and learned the hard way! But off needs to be physically marked on the thermostat. Simply turning the thermostat down to the lowest position does not meet code because the automatic operation of the device still exists!!!

 

[jes25]

Re: 4000 watt htr.

Thanks guys the heater has a switch seperate from the t-stat, breaks both legs. It says nothing about the max OCPD. It does call for #10AWG. I figured a 20A OCPD would not be ok as 16.7 is more than 80% of a 20A. Any code references in regards to sizing circuits such as this is appreciated.

 

[kiloamp7]

Re: 4000 watt htr.

Chances are that 424.3 contains the main rules for this branch ckt.
A 20A branch ckt. would probably be okay, but since you are using #10 wire anyway, why not just use a 25A OCPD.

 

[lady sparks lover]

Re: 4000 watt htr.

Originally posted by jes25:
Thanks guys the heater has a switch seperate from the t-stat, breaks both legs. It says nothing about the max OCPD. It does call for #10AWG. I figured a 20A OCPD would not be ok as 16.7 is more than 80% of a 20A. Any code references in regards to sizing circuits such as this is appreciated.

Does the heater have a motor? For a motor the OCPD would be 2.5 times the FLA, right? I would think think a 40A CB would do the trick, but hey I might be wrong.

[ January 07, 2005, 09:54 AM: Message edited by: lady sparks lover ]

 

[kiloamp7]

Re: 4000 watt htr.

If this 4000W heater is a common "unit heater" then chances are that the fan motor is a very, very small part of the total load.
The resistance heating element(s) are the vast majority of the load.

 

[leggo]

Re: 4000 watt htr.

Is the heater for baseboard heat? I found a four wire Thermostat that has a digital readout and has a definite "off" position.
Leggo,
Ortonville, MI