Immersion heater amperage ( Higher than nameplate )

[Davebones]

We have a new production room with different immersion tanks . These tanks have ( 21KW , 3 phase , 480v , rated 25.3 amps ) over the side heaters installed . Each heater is on a Eaton FAZ-D30/3 breaker being fed with #10 wire . Each of these breakers ( 6 total ) are very hot . Amperage shows they are drawing 29 to 30 amps each leg . The designer of these control panels is saying check the connections and voltage coming in . We checked the connections all good . The incoming voltage is ( 280,281,283 to ground / 482,488,488 phase to phase ) . Distance from control panel to tanks is only about 40 ft . I feel these need to be on 40 amp circuits even thou the nameplate says they draw 25.3 amps as they're drawing 29 to 30 amps . Any other thoughts on this ?

 

[petersonra]

We have a new production room with different immersion tanks . These tanks have ( 21KW , 3 phase , 480v , rated 25.3 amps ) over the side heaters installed . Each heater is on a Eaton FAZ-D30/3 breaker being fed with #10 wire . Each of these breakers ( 6 total ) are very hot . Amperage shows they are drawing 29 to 30 amps each leg . The designer of these control panels is saying check the connections and voltage coming in . We checked the connections all good . The incoming voltage is ( 280,281,283 to ground / 482,488,488 phase to phase ) . Distance from control panel to tanks is only about 40 ft . I feel these need to be on 40 amp circuits even thou the nameplate says they draw 25.3 amps as they're drawing 29 to 30 amps . Any other thoughts on this ?

Immersion heaters are often plus or minus 10 to 20% of what the name plate says. You may have gotten lucky and got some that put out a little more heat than expected based on the name plate. If it bothers you put a different breaker in and run bigger wire.

If you can touch the breakers without being scalded they probably aren't as hot as you think they are.

I doubt that the condition of the connections could cause extra current to flow in the circuit.

 

[infinity]

Do immersion heaters require a 125% factor for conductor sizing? If so the #10 AWG is too small.

 

[LarryFine]

The incoming voltage is ( 280,281,283 to ground / 482,488,488 phase to phase ) .

Those voltages are a tad above nominal, which could explain the high currents.

 

[petersonra]

425.1 Scope. This article covers fixed industrial process heating
employing electric resistance or electrode heating technology.
For the purpose of this article, heating equipment shall
include boilers, electrode boilers, duct heaters, strip heaters,
immersion heaters

425.3 Branch Circuits.
(B) Branch-Circuit Sizing. Fixed industrial process heating
equipment and motors shall be considered continuous loads.

425.6 Listed Equipment. Fixed industrial process heating
equipment shall be listed.

425.8 General.
(A) Location. Fixed industrial process heating equipment
shall be located with respect to building construction and other
equipment so as to permit access to the equipment. Sufficient
clearance shall be maintained to permit replacement of
controls and heating elements and for adjusting and cleaning
of controls and other parts requiring such attention.
(B) Working Space. Working space about electrical enclosures
for fixed industrial process heating equipment that require
examination, adjustment, servicing, or maintenance while
energized shall be accessible, and the work space for personnel
shall comply with 110.26 and 110.34, based upon the utilization
voltage to ground.

 

[Davebones]

Immersion heaters are often plus or minus 10 to 20% of what the name plate says. You may have gotten lucky and got some that put out a little more heat than expected based on the name plate. If it bothers you put a different breaker in and run bigger wire.

If you can touch the breakers without being scalded they probably aren't as hot as you think they are.

I doubt that the condition of the connections could cause extra current to flow in the circuit.

Didn't realize these heaters can be that much plus or minus compared to the nameplate . Thanks for the info . The company that built the controller cabinet is supposed to coming by today to look at this issue . Be interesting to hear what they say ..

 

[petersonra]

Since the code requires UL listing, this is what UL508a says about immersion heaters.

28.3.8 For industrial process heating employing electric resistance or electrode heating technology
including boilers, electrode boilers, duct heaters, strip heaters, immersion heaters, process air heaters, or
other fixed electric equipment used for industrial process heating the field wiring shall have an ampacity of
100 percent of the full-load current rating of the load involved.

I am not sure why UL 508a says 100% while the code says it is to be considered a continuous load which would make it 125%.

31.6.3 Branch circuit protection for industrial process heating employing electric resistance or electrode
heating technology including boilers, electrode boilers, duct heaters, strip heaters, immersion heaters,
process air heaters, or other fixed electric equipment used for industrial process heating shall be sized
based on the ampacity of the field wiring conductors supplying this equipment.

Both of these requirements are kind of odd for UL508a since they generally do not care about anything outside of the control panel.

66.4 Field wiring – power circuits
66.4.1 Field wiring terminals for supply connections shall be sized based upon the sum of:
a) 125 percent of all heater loads;

66.5.4 Power circuit conductors that carry current for a motor or heater load shall be sized for an
ampacity not less than 125 percent of the full-load current.

 

[infinity]

Since this is considered a continuous load the minimum conductor size would be #8 and minimum OCPD size would be 35 amps.

 

[paulengr]

We have a new production room with different immersion tanks . These tanks have ( 21KW , 3 phase , 480v , rated 25.3 amps ) over the side heaters installed . Each heater is on a Eaton FAZ-D30/3 breaker being fed with #10 wire . Each of these breakers ( 6 total ) are very hot . Amperage shows they are drawing 29 to 30 amps each leg . The designer of these control panels is saying check the connections and voltage coming in . We checked the connections all good . The incoming voltage is ( 280,281,283 to ground / 482,488,488 phase to phase ) . Distance from control panel to tanks is only about 40 ft . I feel these need to be on 40 amp circuits even thou the nameplate says they draw 25.3 amps as they're drawing 29 to 30 amps . Any other thoughts on this ?

Bad heater coil(s). Since you have series/parallel circuits and resistance is affected by temperature it’s hard to tell but amps alone.These are resistors. Ohm them out to find the bad one(s). Look at the name plate for each coil. Often you will only know nameplate amps and Volta but that’s OK. Volts divided by amps is ohms.

Often heater coils don’t “fail”. The coils warp out of shape until they touch.

Breakers should get hot. The overload trip function is thermal…it works by generating heat. There is a small bimetallic strip. When it gets hot it bends. When it bends far enough it triggers the trip latch. Look at a UL time current curve. It will tell how long it takes to trip.