Hey guys, customer has a 5000w heater on 240v, she draws 21.5 Amps, long story short it's never had a thermostat on it, so now I'm in charge of getting one put on it. I'm not sure that I feel comfortable with using one of my standard electric heat thermostats because they're rated for 22 amps. Has anyone ever used/seen a 30 amp line voltage thermostat? I'm really coming up empty handed finding one. I'm thinking it might take a contactor and thermostat to make this work.
30 amp thermostat
- Thread starter User Name
- Start date
- Status
hbiss
EC, Westchester, New York NEC: 2014
- Location
- Hawthorne, New York NEC: 2014
- Occupation
- EC
I think you will be fine with the thermostat alone.
-Hal
-Hal
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
I personally prefer the contactor method. Allows for line- or low-voltage control options.
I believe you can get a dry-contact Relay-in-a-Box with a 30a rating, so no transformer.
I believe you can get a dry-contact Relay-in-a-Box with a 30a rating, so no transformer.
James L
Senior Member
- Location
- Kansas Cty, Mo, USA
- Occupation
- Electrician
I'm curious what kind of 5000w heater it is.
Thermostat is not effective on infrared patio heaters, which is what comes to mind with that wattage.
I would use contactor with 120v coil. That way you leave yourself the option to swap to a timer later (if it's in fact a patio heater)
Thermostat is not effective on infrared patio heaters, which is what comes to mind with that wattage.
I would use contactor with 120v coil. That way you leave yourself the option to swap to a timer later (if it's in fact a patio heater)
texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
I would not use a direct line voltage thermostat for this. And using a standard contactor has issues, particularly pull in noise in many applications is very objectionable. Use a Honeywell/Aube relay made for this purpose. They are potted and noiseless and last for ever.
See here: https://www.supplyhouse.com/Honeywell-Home-RC840T-240-240v-Relay-w-Built-In-24V-Transformer
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
This honeywell T-stat says it is good for 5280 watts. It also has a positive off.
drcampbell
Senior Member
- Location
- The Motor City, Michigan USA
- Occupation
- Registered Professional Engineer
When a device is rated and listed for 22 amps, passing an actual 22 amps through it is fine because that rating already includes a margin of safety and a margin for error. There's no need to select a 30-amp device to add an additional margin.
texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
I should have added that another reason to use an Aube relay is it opens up a whole lot of possibilities for the stat you use. Invariably it seems that when ever I have installed a line voltage stat the call eventually comes that they want a stat with modern features.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
It could even allow wireless or phone control.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Then they should have purchased a unit with on board controls and a wireless remote
Some think have temp sensor in the remote and you use that to control your setpoint. At least I have seen that with fireplace remote controllers.
That relay does look kinda handy, it is only rated for 22 amps as well, so I'm not sure I would be gaining anything that would help with giving me some wiggle room on the amperage. But if you guys think I'm ok to use a 22 amp stat on a 21.5 amp load I'd probably stick a regular line voltage thermostat in like I was going to do.
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
The King and Qmark heaters that are 3kw that and larger I have installed have internal relays with 24 vac control transformer.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
I wired a 7500 watt unit heater yesterday. Some off brand name sold at big box store. It had electronic controls on the face of it, wireless remote, and the contacts for heat elements are permanent relays on a PCB, and look like they possibly wouldn't have as heavy of contacts as what is in typical bimetal 22 amp wall thermostat. Don't know how easy this would be to find replacement parts for when it fails or how much it would cost. 22 amp wall thermostats are relatively inexpensive and easy to get at least.
- Status