Frozen Evaporator Motors

[Brian_UK]

Went to our local ice-cream manufacturer today to check the cold stores, one at -27°C the other at -24°C.

On the whole not too bad, they had lost a controller due to recent power fluctuations but soon fixed.

The problem they have is with the evaporator fan motors freezing up during defrost, the bearings dry (frozen grease?) and the motors lock up.

Does anyone have any knowledge of using heaters to protect the motors and also the fan blades from sticking to the fan cowl.

[subzero*psia]

Can you tell us any more? You say the motor won't start, but also mention the fan blades are sticking to the cowl? How are the blades sticking... there should be no frost on the cowl.

How often and for what length of time is there a defrost cycle?

Do the defrost heaters completely clear the coil before returning to the cooling mode?

This is ice cream... do they manufacture it or buy it and at what temperature does the ice cream come into the cold space?

-24°C and -27°C is really not all that cold for ice cream... it works if the ice cream comes in "brick hard". I would be looking for a temperature of -29°C to -32°C. But again... receiving temperature may be a concern and not the holding temperature... just thinking. Most times I have seen fans freeze up on ice cream cabinets it was due to high latent heat load...

[Derek]

Last time I went though this the problem was traced to the condensate drain line (no effective P trap). Warm air ingress was frosting up the coils around the fan and placing huge load on them. The end result was a pile of bent fans and broken motors. Difficult to find as the evidence disappeared quickly.

A typical customer to blame but never said sorry or paid for the pile of damaged parts ISTR.

Who's evap is it?

[subzero*psia]

Another problem is missing insulation or seal-gum around suction or liquid lines entering the cabinet. If the unit is a walkin, another common problem is worn door sweeps.

[Andy]

Hi, welcome to the world of industrial refrig. Most cold stores suffer from the afore mentioned problem, it is due to moisture in the air sucked into the store by open doors. Usual icecream stores have propeller type high air flow fans fitted with pheriphial heating initiated during defrost and terminated after the drain down period. I am at the moment pricing a dehumidification and refrigeration project for a coldstore loading bay, the idea being to remove the moisture before it sticks to the evaporators. Also I may be wrong but you temperature see very low, with most stores I work in running at -25c return air, this low temperature will lead to even more moisture being sucked in. As for the grease unless they are very small fan motors the grease freezing will not be a factor.
I spent 3 hours today just removing ice from cooler in a icecream store, the door had been broken and moiture had been sucked right through the evaporator building up in the area behind the fans tripping them out, so you are not on your own.
Regards. Andy.

[750 Valve]

I'm with Andy, sounds like door constantly open. As a short term fix you could extend dripping/drain time to allow droplets to clear off fans or as Andy suggested raise storage temp to approx -25C to reduce quantity of moisture sucked into room.

[subzero*psia]

Have you solved the problem yet? Do tell us as we have a several possible solutions posted on here and we are all waiting to see how you solved it.

[Brian_UK]

Sorry Dean, no I haven't solved this one yet but the suggestions all hold good.

The main door seal wasn't making because the door slides had come loose

They do have a drainage problem aswell....there are two ice mountains below one of the evaporators which the guy tends to clear out by driving his fork-lift truck at them

Also they lost one or the compressors a few days ago which I think was due to an oil separator problem along with old age.

They keep promising to shut down the cold store for maintenance, firstly Oct the Feb then Oh I don't know. These ex-farmers are a breed on their own !

[Andy]

Hi, Brian, having fun? Loads of coldstores seem to be owned by ex-farmers, I can think of one or two and yes they are mostly a law unto themselves. With regards to emptying the colstore for maintenance, we don't the customers just don't like it, anyway most of the stores I work in have anything from 5000 ton up product in them, it would not be possible to empty them. We work away with suits on (deep freeze) mostly our coolers are de-iced, after clearing the drains by hot wash power washers with the nozzle removed. As for access we us either platforms or reach trucks with safety cages.
It's all hard work and none too warm, but mostly the stores I work in are under contract, so you make certain the ice does not build as it is you clearing it. As for freeze ups due to door, seen by the snow trail, we charge for them, it soon teaches the client to keep the door shut and in working order.
Regards. Andy.

[Brian_UK]

Originally posted by Andy
Hi, Brian, having fun?

Yes and no Andy...

I can't think exactly what our service period is off hand; it's either twice or three times a year so keeping a decent track of what's happening is difficult.

Going back some months when the client was at the Goodwood Festival of Speed we had several overnight callouts because his -27°C coldstore wasn't holding temperature.

Go inside - one evap with 3 fans running, the other with only 1 fan running; both evaps fed from the same compressor (R404a).

All sorts of fun spent there ! Ended up on Sunday night stripping out one fan from the good unit to put in the other one along with defrosting, de-icing fans and motors - oh the list goes on....

Clients comment - Oh yeah, we've only had one fan running for a while. Kept meaning to get it fixed etc etc

Jeez, just the sort of thing you need isn't it ? I know we all get and it keeps coming in buckets full

[herefishy]

The EVAPS wouldn't happen to be Russell brand, would they?

I had constant bearing failure on Russell OEM motors. The box said "permanently sealed bearings". But when I took a bad bearing to the bearing store, Mr. Bearing told me tht the bearins in the motor were "shielded", not "sealed.

[JONAH]

hi brian,
ive spent many an afternoon clearing ice from stuck evap fans,doesnt your blowers have periheral heaters on them to help prevent edge of blade sticking to cowling an then triping out fan motors?extending drain down i find makes matters worse due to residual heat/steam rising and adhering to cold surfaces ,cowling,tips of blades etc from defrost heaters even when terminated after DEF.

[Simon Butler]

Used to get the problem of ice holding fan onto fan blades a lot with a certain large frozen food chains coldstores, trouble was the KS range of searle evaps produce steam when defrosting due to only having two defrost heaters which therefore have to get very hot. Actually got Searle to recognise the problem and they supplied peripheral heaters to be retrofitted to the blowers.

(Still don't fit them as standard though)

Simon.

p.s. something we tried before getting the heaters was smearing the cowlings with vaseline or grease to make the water bead and stop it sticking!

[Brian_UK]

Thanks Simon.

Yes they were Searle but the problem is no longer mine now as I have left that firm and area.

I must admit that I like the sound of the vaseline though, simple but effective - always the best !

[Dan]

Brian. I enjoy all your posts, but you have a signature that states that you you are presently not employed. Do you also have a business card that says the same?

[Brian_UK]

LOL Dan.

Yes, now that my house move is over I am now having to seriously look for work again but I think I will pass on the business card idea.