Condensor and evaporator fans

[ktmtragic]

I am quoting a job for a refrigiration company and I would normally use a seperate contactor and overload for each 3 phase fan motor (4 on each unit). They have said one contactor for each evaporator/condensor is sufficient. What are your thoughts?
ktmtragic

[nike123]

If fans having internal thermal protection (which they usually do) than it is OK.

[Magoo]

Use one contactor for each evap, and downstream of contactor use individual MCB's for individual protection. Saves a truck load of money on individual contactors and overload protection

[Magoo]

added,
if you use a lockable MCB, there is no need for individual local fan isolators at the evaporator or condenser. A huge saving in switches and labour installing.

[nando]

for the condensor it is better to use separate contactors, this you can put on and off with a pressostat; to control the condensortemperature

[mbc]

I think it is better you use one contactor for each Evap. And also one for condenser and all fan should have separate manual over load current for each fans. And also it is better you control condenser pressure by putting pressure switch on it

[lavurk]

Better to use separate contactor and overload relay for each Evaporator/Condenser.This will give safe protection and easy maintenance

[Terron]

I agree with Nando, It's better to be able to control each fans cut on and cut off pressure to maintain a constant and steady head pressure. I would give the customer an option and let them choose.

[NoNickName]

There is no definitive answer. One contactor and MCB per fan gives you more selectivity, one contactor and MCB per evaporator/condenser gives you lower cost.

[fridge-spark]

If it was me I would connect the evap fans on 1 contractor / overload and the condenser fan in a pairs or on there own contractor / overload for closer control. I would also wire the control circuit for the compressor(s) via the n/c of the overload to stop flood back if the evap fans fail. HP switch will look after the head pressure.

[chilliwilly]

added,
if you use a lockable MCB, there is no need for individual local fan isolators at the evaporator or condenser. A huge saving in switches and labour installing.

Good suggestion, but the isolator has to be local to the machine it isolates. You would have to use one of them transparent membranes to protect the mcb that split and perish away, or one of those hinged enclosures that always break off.

Overall it would be less hassle for better a PPM, just to install local isolators fed by one contactor and O/L for each condensor unit. Unless of course the fans are larger than 370 watts, in which case a seperate O/L for each fan.