Baseboard - 208v - temp range

So I’m inspecting this condo… It’s got electric baseboard heat… I turn them all on and get my thermal camera out. 158*, 160*, 225*! What?
While surveying I see this decal. “Warning! 208v heater, Do not connect to a 240v suply”… Now, after some research, I see that’s a reference to a 3-phase power supply and a better system.
Q? - What am I looking for in the panel to confirm proper configuration?
Q? - What’s" too hot" for an electric baseboard heater.? Fins or cover/shield? 225* at the core sounds hot to me…

Q? - I’m seeing 8-12" clearance recommendations, say for drapes, from baseboard heater units. Sound right?

We all know to call out electrical outlets above Baseboards, right…?

Thanks. Bill o


What is the voltage at the panel . I expect it is 120/240 .
So yes the heaters are designed for 208 volts and will fun hot and their life will be shortened and likely burn our soon .
Yes they are way too hot .
Yes drapes well above and no out lets above the heater .
Turned on my heaters and they are 140°F now

Without knowing the voltage connected to the unit you have nothing to go on.

As Roy said, what is the panel voltage?

Perhaps it is 3-phase 120/208.

225 at the core doesn’t mean much.

What are the surface temps?

You need more info.

Thanks for your input…
The panel appeared to be a 120/240 service…One Neut with two 120s
Yes I agree, it’s the baseboards cover/shield that one would be concerned with for potential overheating…The 220* baseboards cover was way up there, so of course I touched it to see how it felt… HOT! but, no burned fingers…
I spent a bit of time trying to find out what the CPSB (Consumer Product Safety Board) & NFPA (National Fire Protection Assn) might say about it , and found a couple studies on it, including UL1042.
I didn’t get what I’d hoped for but learned some…
Combustable temp range of “Cheese Coth” (Cotton) is 360*
By overheating baseboard heaters with cloth, it’s not the cloth that
Overheats and enflames, it’s the wiring connected to the heater that
Melts it’s shield and somehow ignites. (Heaters are destroyed in fire and
Specifics there are limited) No kidding…
Internal coil temps seem to be in the 160* range.
Commercial baseboards allow for a different standard.
Thermal control (Thermal shut offs) were tested by CPSB in 1983
Implimented thereafter. UL 1042. Last updated in 1995.
So a modern baseboard heater (+1983) will have ID lableing (UL Data Plate)
And an integrated thermal shut-off.
Clearances from combustibles are 8” above and probably 8” in front.
(Comments there ranged from 3” to 3’…)
I believe 3” is to allow proper convection and 3’ is to allow warm air to circulate…
Since 8” is the Clearance from combustibles…I like that… (for safety)
Lifespans of baseboard heaters vary quite a bit, but manufacturers say 18 yrs is an avg… Water temp recommendations are safe for children at or below 120*. Children do burn easier…A problem inherent with hot water from the tap is that the temp starts off cool then gets hot.
Third degree burns occur to skin at 130*-140. Of course, the longer one is in contact, the more serious the burn.
The inspection…I called for further evaluation by an HVAC Pro. “Beyond the Scope” and hopefully I’ll learn something there…
If not I’ll continue to call out baseboard covers/shields over 160* for sure…
Bill O

I would measure the voltage between the two hot lugs at the panel if its a single phase panel, or all 3 lugs if its a 3 phase panel. If you get around 208 volts your ok. Anything over 215 volts means its not a 120/208 volt 3 phase utility supply to the building.

208 volt heaters are created for buildings with a 3 phase 120/208Y services. A 240 volt heater will produce much less heat when connected to a 208 volt supply. A 4000 watt 240 volt heater will only run at about 3000 watts at 208 volts, a 25% reduction. To solve this problem manufacturers offer 208 volt rated heaters. However, not all 208 volt heaters can handle 240 volts, since at 240 volts a 4000 watt 208 volt rated heater will produce 5,325 watts. Some cant handle the excessive heat hence the sticker.

If curious about the voltages on the sticker and where you find them:

240 volts usually comes from the typical 120/240 single phase service found in most homes and some apartments. Less likely is a delta high leg service that gives both 120/208 and 240 volts. (other services can give 240 such as 240/480 split phase; 138/240Y; 240 ungrounded delta ext, ext but those apply to industrial environments and not worth worrying about)

208 volts comes from 3 phase 120/208Y services. Its the norm in commercial, a lot of apartments and houses in cities. Often individual apartment units and houses only get 2 legs and a single phase panel but the 2 hots read 208 instead of 240. 120 volts is still found hot to neutral.

277 volts comes from 277/480Y services. Very common in larger commercial, industrial and high rise buildings. 277 volts runs commercial lighting, heaters; while 480 volts runs motors and elevators. 480 volts is also stepped down to 120/240 or 120/208 via transformer for outlets and everything else you would normally find running on 120 volts. Not something most HIs will encounter in residential settings.

Long reply but hope it helps. :slight_smile:

Thanks Martin,
After reading your comments I googled up 3-phase power and got more than I asked for on Wikipedia… After a couple reads, I’ve begun to understand it…

Searching: "Check voltage on 3-phase panel-youtube " (Jones Heating and Air) gave a hands-on voltage check video.

Bill O

Bill O