OVER HEATING EMT

Status
Not open for further replies.
E

EPDUKES13

Member
Location
EL PASO, TX
Heater-
15kw, 3 phase, 208 v, #6 cable, 50 amp breaker, in 3/4" EMT, 180' run to panel?
There are 4 similar suspended unit heaters, one of them has a breaker at 110 degrees and the EMT at 95 degrees, l tighten all connections at unit, disconnect and breaker panel!:?


What next?
 
EPDUKES13 said:
Heater-
15kw, 3 phase, 208 v, #6 cable, 50 amp breaker, in 3/4" EMT, 180' run to panel?
There are 4 similar suspended unit heaters, one of them has a breaker at 110 degrees and the EMT at 95 degrees, l tighten all connections at unit, disconnect and breaker panel!:?


What next?
Click to expand...

Did you take amperage and voltage readings?
 
Sounds like inductive heating. Are you sure you have the phases grouped correctly? You may have a BBC running down the conduit. Instead of ABC phases
 
EPDUKES13 said:
Heater-
15kw, 3 phase, 208 v, #6 cable, 50 amp breaker, in 3/4" EMT, 180' run to panel?
There are 4 similar suspended unit heaters, one of them has a breaker at 110 degrees and the EMT at 95 degrees, l tighten all connections at unit, disconnect and breaker panel!:?


What next?
Click to expand...
Have you compared the four heater nameplate actual ratings? You know, the nameplate voltage, current and kW ratings?
 
Welcome. As others have mentioned, amperage and voltage readings would be prudent. What are the temperature readings of the other conduits and breakers, and what is ambient? How and where these temperatures measured? A 15kw 208V heater should pull ~40A on each phase, and AB, BC, and AC should all be roughly the same; any significant deviation would indicate to me a blown heating element or burnt conductor.

The breaker could be warmer than others for a variety of reasons, as could the conduit. Me, I'd check the current, voltage, breaker connection to the bussbars, adjacent breaker temps, and the conduit in multiple spots, as well as the conduit fill of the warm conduit. 3/4" EMT is only good for 4 #6 wires, so if someone ran another circuit beside the heater, it's most likely overfilled.
 
iwire said:
That seems unlikely to me.
Click to expand...

Me too, if for some reason there were 2 conductors of the same phase and 1 of the others, the heater would not work correctly; one element would have 0V across it, and unless the fan was single phase it wouldnt work at all. Nevertheless, it should be a simple visual check, tho voltage readings would reveal it as well.
 
EPDUKES13 said:
Heater-
15kw, 3 phase, 208 v, #6 cable, 50 amp breaker, in 3/4" EMT, 180' run to panel?
There are 4 similar suspended unit heaters, one of them has a breaker at 110 degrees and the EMT at 95 degrees, l tighten all connections at unit, disconnect and breaker panel!:?


What next?
Click to expand...

Voltage reading; 209.7, 209.9 & 210.2
amp; 42.1, 42.8 & 42.7
All four heaters are exactly the same- 15kw, 208 volts, 3 phase
ambient is 75 degrees, the other heaters are about 90-95 degrees on the EMT and breakers are the same temperature.
 
EPDUKES13 said:
Heater-
15kw, 3 phase, 208 v, #6 cable, 50 amp breaker, in 3/4" EMT, 180' run to panel?
There are 4 similar suspended unit heaters, one of them has a breaker at 110 degrees and the EMT at 95 degrees, l tighten all connections at unit, disconnect and breaker panel!:?


What next?
Click to expand...
Does the warmer one run more often then the others? Temps you mentioned are not really that high IMO if there is a lot of run time. Conductors do produce heat when carrying current, you get into a place with a lot of fairly continuous loads and your temps are normal or even on the low side.
 
Internal breaker problem

Internal breaker problem

We are talking f degs correct. The 95 deg pipe is nothing, my heat tunnels run the same way or more in 3/4". The breaker temperature is either bad stab connection in back or bad breaker if it is reading differant from the others.
 
EPDUKES13 said:
Voltage reading; 209.7, 209.9 & 210.2
amp; 42.1, 42.8 & 42.7
All four heaters are exactly the same- 15kw, 208 volts, 3 phase
ambient is 75 degrees, the other heaters are about 90-95 degrees on the EMT and breakers are the same temperature.
Click to expand...

Then there is likely no problem. The odds of 4 separate heaters and 4 different circuit breakers all having simultaneous overheating issues is virtually zero. 180' of #6 with a 42A load (x3) will dissipate roughly 360W of heat thru I2R losses. That's going to warm up the conduit a bit. If the heaters run for a long time, 42A will also cause a small temperature rise on the breaker. 20*F over ambient is not a cause for concern imo.

Your voltage and amp readings tell me there are no problems with the heater elements or a burnt phase conductor. Running several heavily loaded breakers next to each other in the panel can cause some higher temperature reading.

Are any of the heaters blowing heat on or near the conduit? That could be the cause of the warmer temperatures.
 
Status
Not open for further replies.
Top