Searle Evaporator Heaters

[Abe]

Im not sure if anyone has experience of Searle evaporator , heater giving problems.

I dont have the Model number , but its a biggish one, 3 fan motors.

When I connected the heaters , the circuit breaker tripped, So I disconnected the heaters and left in on a forced air defrost.

Customer adjusted stat to minus 5 c,m so I go today to a iced up coil.

Electrician was on site so I ask him to check integrity of heaters.

It showed 4 ohms on earth leakage test, which he said was fine.

I connect heaters direct to circuit breaker, not via contactor and leave them on for about an hour.

Pulling 18 amps in total.

After an hour I hook the electrics back into contactor. This time circuit breaker trips, and in so doing takes out a fuse from the main distribution board.

I check wires................Heater is now down to earth.

Too late.............Electician has left site by now.

Going back tomorrow................Why does it now show down to earth??

Im going back tomorrow, check the wires up in the evaporator itself.

How are these heaters connected, Ive connected them in parrallel. Might be three or four heaters embeddded within the evaporator.

Maybe one of them is faulty. I dont know. Can only check tommmorrow.

[Brian_UK]

Firstly, did the sparky test with a Meggar tester or a simple multimeter?

If it was a multimeter then the earth fault may not show up.

The heating elements are normally supported inside the sheath using a fibre of some sort. It is possible for the element to buckle and contact the outer sheath - ergo earth fault.

You also need to confirm that the electrical connections are all dry, sounds silly but when first powered up the terminals may have been dry, defrosting then encourages water to form - possibly around the terminals. The heat keeps them dryish, you then depower the heaters but the water keep dripping onto your terminals.

Yep, parrallel is good. Is there a problem with the contactor ?

[Abe]

Prob terminals got wet Brian.............

Ill check throughly tomorrow

Sparky tested with a megger

[chemi-cool]

Hi Abe,

I assume that the heaters are new, it is of a good practise to leave the heaters on for an hour or so so they will be completely dry.

Chemi

[fixit]

Have you cheked the contactor without the heaters connected, the heaters worked ok on the breaker.

[Abe]

Ok sorted out problem today. Evaporator was an old one, not new........

Had two heaters, one midway, one at bottom.

Bottom one definately down to earth, burnt out.........

Ive connected just one heater on at moment, adjusted the stat to cut off at 0 celcius.............
Timer set to initiate one 30 minute defrost every six hours

and hoping that the evaporator does not ice up

Heater pulling around 8 amps

[Brian_UK]

It's nice when you find the fault. It's not always nice having to fix it - but....

[frosty74]

i have had this problem myself before but to keep the coil defrosting on 1 heater until the other is replaced i repositioned the evap probe into the top of the evap coil. the heaters on the searls are usally good heaters anyway so if coldroom usally work ok on 1 heater also

[Derek]

Aiyub

Suspect you have a K series cooler probably a 360. If you give Searle a call they should have the go/no go resistance and power consumption data for the heaters depends how tech you want to get. Each element used to have a part number etched on it. Searle are usualy pretty helpful and thats not just cause they used to employ me. Serial number is a big help!

[Abe]

Next time Im on site Ill have a look

Thx

How easy is it to remove the heater, the bottom one.........I have no space to slide it out

[jan behnke]

have you checked to see if they were not 3PH heaters and you Have wired them up for 1PH, ie if you had 3 pairs at 3PH they would be rated at 110v and you left them on for over a hour they would glow in the dark

[Abe]

No they are single phase

[Derek]

Depend on the model and age but you can drop the drain tray and the four botton case fixings to give you some space and go in with a long (very) nose pair of pliers...

I accept no blame for any damage.....

[Jus Walker]

heaters on searle k 360 and large evaps like that give great difficulty in removeing heaters due to the weight of the coil which does bend ever so slightly in the middle. Sometimes is is best to drop the evap and lay upside down to remove the heaters. But if the faulty heaters have blown inside the coil it is nearly impossible to remove. might be wise to drop the evap to change the heaters if you dont have the room to change the heaters.

[willies boy]

you need at least the length of the element or you will break it on install(about 30inches)