Evaporator fans going on overload

[AndyHX]

Hey guys, i have an 6 fan evaporator coil in a freezer room and there are 2 fans that are drawing almost twice the current that they are rated for and going out on internal overload. I replaced 1 as i thought it was faulty but the new fan draws the same current.
The evaporator has no divisions between fans and evaporator so i got one made up and this has reduced the amps drawn by effecting the air flow.
The question is i am not quite sure what the division has done , has it slowed the fan down by directing more air through the coil ?? If a fan is drawing to much current is it over speeding ??
thanks for any thoughts on this
Andy

[AndyHX]

The evaporator has no divisions between fans and evaporator

I meant no divisions between each of the fans along the front of coil.

[nike123]

Hey guys, i have an 6 fan evaporator coil in a freezer room and there are 2 fans that are drawing almost twice the current that they are rated for and going out on internal overload. I replaced 1 as i thought it was faulty but the new fan draws the same current.
The evaporator has no divisions between fans and evaporator so i got one made up and this has reduced the amps drawn by effecting the air flow.
The question is i am not quite sure what the division has done , has it slowed the fan down by directing more air through the coil ?? If a fan is drawing to much current is it over speeding ??
thanks for any thoughts on this
Andy

Are there single or three phase?
Did you checked voltage and voltage balance (if 3 phase) on each fan?

[cadwaladr]

sounds like a wiring problem to me ,how are the motors fed their power,check the terminals,i presume the motors are identical in every way?

[chemi-cool]

What you have to do is disconnect all of them and check them one by one.

Sorry its more work but the way you describe the fans connection I don't see any other way.

[AndyHX]

The fans are single phase and the one i was having trouble with is now drawing correct amps due to the aluminuim division i have rivited in between the fans and back to the face of coil.
But how has this worked is what i want to know??? the air flow has changed and reduced the amps??

[monkey spanners]

Are they spinning the correct way?

Are the fan blades the correct pitch?

[Brian_UK]

Any fan motor is designed to handle a certain airflow rate at the rated amperage.

Allowing the fan to handle more air will increase the amperage into overload conditions.

You would find the same effect if you had an enclosed fan, in an AHU eg, and opened the fan access door.

What you have achieved in fitting the divider is providing the fan/motor with the correct resistance (duct) for the fan blades.

I was going to suggest that the wrong blade had been fitted but the fact that you have brought the fan back onto it's curve cancelled that.

[old gas bottle]

all sounds a bit odd what size are theese fans,blade and running current ? all the capacitors o/k ?if they have a multi core wiring supply for various voltages and reversal,is all that o/k. bit more info matey please.

[AndyHX]

Brian Uk , thank you for the explaination , it makes sense now. I just got some more info today about the coil and the manufacture messed up design and the fins are to closely spaced , not sure if that is part of problem or a seperate issue.

Old gas bottle
fans are single phase 350mm diameter , rated at 0.8 amp and were drawing 1.2 amp until i put division in and now drawing 0.8 so it looks all ok

[cu2chat]

Fin spaceing should have no impact on amprage of motors fitted to a cooler by manufacturer check min max limits of cooler to chamber walls or go over your wiring again