Fans sticking in ice

[Chunk]

Hello

I am having a problem with some Rivacold freezer coldroom evaporators that regularly build up ice around the rim of the holes where the evap fans sit.

This is not isolated to just one unit and i am having problems on various sites.

I have fiddled around with defrost settings and this is not caused by doors being left open for long periods of time.

I have used one of my own sites as a test,i have two identical coldrooms that both have the same problem.On one of them i have fitted door switches to turn fans off when door is open and i have also installed heater tapes around the rims,but this has not helped at all.

We seem to be burning out a lot of motors and i cannot think of anything else that might help.

Has anyone else had experiance of this problem and found a way of dealing with it?Any help would be appreciated.

[fowlie]

are these the old style ones with the round blue baffles as we had probs with these due to long/hot defrosts causing moisture from roof to run down onto gaurds/fan blades and jam fans,it sometimes caused the capacitors to heat up and fail.hope this is of use

[US Iceman]

A couple of things to check out...

Is the defrost termination working? If the defrost is too long the coils may start to steam a little towards the end of the defrost cycle. The moisture tends to collect on anything colder than the dew point temperature of the moisture coming off of the coil.

The second thing I can think of off the top of my head is to verify the coil has dripped dry (after defrost) or if there is a post defrost cool down which allows the moisture droplets to refreeze onto the coil.

On a freezer unit the air velocity through the coil is high enough to pull moisture off of the coil, particularly after a defrost.

And, since this problem seems to be rampant in other locations it would seem to be a similar problem in all of them.

That's about the best advice I can give at this point without any more details.

Hope it helps.

[monkey spanners]

On a freezer room i installed with either (can't rememner which) Friga Bohn or LuVe evaps it came with metal heater loops that went round where the fans are mounted to stop this happening.
Do Rivacold offer these type of things as an option for your evaporators?
Fit some contactors and overloads to the evap fans, will work out cheaper than new motors.

On another site years ago a friend of mine drilled a 25mm hole in the bottom of the fan cowl to let any water drip out due to this problem.

Jon

[US Iceman]

...it came with metal heater loops that went round where the fans are mounted to stop this happening.


This sounds like a problem the factory couldn't solve so they used a belt and suspenders type of approach. I don't think I have ever seen heaters fitted to a fan cowling, so .... there must be an underlying issue with the design or operation.

I can't think of a reason why these should be required unless there is something specific to the coil arrangement which causes it.

[Chunk]

are these the old style ones with the round blue baffles as we had probs with these due to long/hot defrosts causing moisture from roof to run down onto gaurds/fan blades and jam fans,it sometimes caused the capacitors to heat up and fail.hope this is of use

Hi Fowlie

No these are brand new with the motor built in with a wire mesh cage.I am trying to find a picture to upload.

[Chunk]

This is not just a problem with one type of unit as we have various models.

The defrost settings i have used are as follows:

Fans off in defrost
Evap temp to end defrost 20*c
Drain down time 10 minutes
Suction temp to turn fans on -10*c
Defrost duration 20 minutes.

The rims are the only place that ice forms,i have no ice on front or inside unit and i have no water running down from the roof.

[fowlie]

is that the fixed blade type i think ive had this happen in a room,ice would form on the fan gaurd and jam the motor causing it to burn out.got round this buy moving the defrost probe to stop defrost cycle staying on to long and hot.but because of it being a tesco site i couldnt change operating parameters.

[Chunk]

The units are the RC and Rcm models as featured here

http://www.rivacold.com/prodotti.php?action=view&id=31&cid=3

Rivacold do not supply much apart from lots of replacement motors.

This is for a Sainsburys site and all parameters can be accessed.When they were first installed last year,the standard spec was to defrost for 30 minutes and terminate at 30*c evap temp but i have lowered everything due to heavy condensation of the ceilings.

This is happening on electric and sat gas defrosts.

[fowlie]

the only thing i would do would be to lower the drain down to 3min as it could be that the 10min is allowing the moisture to freeze on the gaurd.ive had the same prob and those fan motors arent cheap.

[chillin out]

What kind of ice is it?
White fluffy kind, white solid kind or clear solid?

Chillin:):)

[Chunk]

the only thing i would do would be to lower the drain down to 3min as it could be that the 10min is allowing the moisture to freeze on the gaurd.ive had the same prob and those fan motors arent cheap.

We installed these last march so they have been in about a year and i looked in my diary and i have replaced 7 of them so far.If i catch it quick enough and just knock the ice off with a screwdriver they are normally alright.(This is just one store,so god knows how many have been replaced in others)

These motors have an inbuilt thermal overload,but i have found if they jam up too many times they wont start again.

[Chunk]

What kind of ice is it?
White fluffy kind, white solid kind or clear solid?

Chillin:):)

White solid kind.

I just checked and they have a 5mm clearance between blade edge and rim,so it doesnt take a lot of ice to build up.

[Chunk]

the only thing i would do would be to lower the drain down to 3min as it could be that the 10min is allowing the moisture to freeze on the gaurd.ive had the same prob and those fan motors arent cheap.

If i lower the drain down we are back to the old problem of the drip tray icing up,this is why i raised it to 10 minutes.They were originally set to 2 minutes and the fans were jamming then too.

[fowlie]

dont know how you could get around this,could altering the space of the gaurd/fan from the evap maybe stop moisture getting blown onto the rim. by fitting some washers or even putting a small layer of silicone seal on rim to stop water from staying on rim.
we just get the ems ist to go round with a hammer

[Chunk]

dont know how you could get around this,could altering the space of the gaurd/fan from the evap maybe stop moisture getting blown onto the rim. by fitting some washers or even putting a small layer of silicone seal on rim to stop water from staying on rim.
we just get the ems ist to go round with a hammer

Moving the fan is not an option due size of the blades.I havent tried the silicon so i shall give that one a go in the morning.Thank you.

Sainsburys got rid of all their ist`s a long time ago,which is why we have to work harder now. ;-)

[chillin out]

Sainsburys got rid of all their ist`s a long time ago,which is why we have to work harder now. ;-)
I heard they are getting them back.

Chillin:):)

[Chunk]

I heard they are getting them back.

Chillin:):)

I do hope so,they are good for unblocking cabinet drains.They have put a few in some of the larger stores as a trial,but i dont know if it will be permanent.

[Grizzly]

We installed these last march so they have been in about a year and i looked in my diary and i have replaced 7 of them so far.If i catch it quick enough and just knock the ice off with a screwdriver they are normally alright.(This is just one store,so god knows how many have been replaced in others)

These motors have an inbuilt thermal overload,but i have found if they jam up too many times they wont start again.

Hi Chunk.
You say you fitted a peripheral heater around the rim and this did not work.
Was this powered up on defrost start-up?
What other motor overload safety is fitted.
Ie Do the motor contactors hve overloads fitted to them and if so what are the trip amp settings?
If not fitted could they be fitted?
The reason I say this is because, it is a common fault within Cold Stores. For a fan to stop with one of it's fan blades vertical.
So that during defrost / drain-down the resultant water runs down the blade.
Bridging the blade clearance between it and the cowl and then freezing.

The end result is a fan that cannot be reset and a safety cage trip up to the errant fan.
Where usually a sharp "tickle" with a hammer on the cowl at the point of contact, relaeses the fan.
Allowing a reset. The fans can be quite large sometimes (average size 30" woods type).

Is it standard practice for there to be only the internal thermister as the electrical safety?
Or are these panel like what seems everything else "supermarket" done to the tightest budget?

And finally

[Chunk]

Hi Chunk.
You say you fitted a peripheral heater around the rim and this did not work.
Was this powered up on defrost start-up?
What other motor overload safety is fitted.
Ie Do the motor contactors hve overloads fitted to them and if so what are the trip amp settings?
If not fitted could they be fitted?
The reason I say this is because, it is a common fault within Cold Stores. For a fan to stop with one of it's fan blades vertical.
So that during defrost / drain-down the resultant water runs down the blade.
Bridging the blade clearance between it and the cowl and then freezing.

The end result is a fan that cannot be reset and a safety cage trip up to the errant fan.
Where usually a sharp "tickle" with a hammer on the cowl at the point of contact, relaeses the fan.
Allowing a reset. The fans can be quite large sometimes (average size 30" woods type).

Is it standard practice for there to be only the internal thermister as the electrical safety?
Or are these panel like what seems everything else "supermarket" done to the tightest budget?

And finally

Hi Grizzly

I fitted the heater around the rim and it is wired to be on permanantly.
I have on control board controlling everything and it has a 5amp breaker built in for the fans and the fans have internal o/loads.The fans are powered directly from controller(no contactors).

I sat in the coldroom today and watched a complete defrost cycle.It all went well until it finished its drain down and the fans started.you could actually see water being sucked out of the evap and some of the water was settling on the rim,the fan as it was spinning,was keeping the water in place and then started to freeze.

These are newish coils,so the fins are not bent and shouldnt really have anywhere to trap water.10 minute drain down is long enough for it to drip.

I used Fowlie`s magic mastik trick to see if this helps,but i am sure this is a design fault due to the shape of the rims and the high power of the fan motors.

The defrost only lasted 16 minutes and i terminated it at 10*c evap temp.Left it at 10 minute drain down.They will work for about 4 days now until the ice is thick enough to stop the fan.

The weird thing is though,the ice forms on the side of the rims,not top or bottom.

[US Iceman]

It all went well until it finished its drain down and the fans started.you could actually see water being sucked out of the evap and some of the water was settling on the rim,the fan as it was spinning,was keeping the water in place and then started to freeze.




The second thing I can think of off the top of my head is to verify the coil has dripped dry (after defrost) or if there is a post defrost cool down which allows the moisture droplets to refreeze onto the coil.

On a freezer unit the air velocity through the coil is high enough to pull moisture off of the coil, particularly after a defrost.


The water is distributed around the fan nozzle by the air velocity, which is highest at the nozzle. After defrost if the coil is not allowed to drip for awhile and then refreeze the water gets pulled off of the coil by the face velocity (air velocity over the air entering side of the coil). Freezer coils almost always have a high face velocity while cooler coils have a lower face velocity since they are always wet.

You might try to find a Klixon thermostat set for a temperature slightly below 0°C to allow the coils to cool down and refreeze (liquid solenoid on, fans off) the water droplets before the fans start. Or a timer for a fan delay but this might require some trial and error adjustments.

[Chunk]

Hi US Iceman

Thats the problem i have,everything is controlled by temperature probes running off one controller.Air on,air off,evap in,evap out.

After the 10 minute drain down,the suction temperature has to reach -10*c before fans start,so in theory the coil should be freezing,but i am getting small droplets of water being sucked out.

There are no extra facilities to add things like Klixons and fan overloads due to the electronics.These electronics tell the unit what to do,and if anything deviates from what the controller says,then the store computor starts throwing out alarms.

In theory,all i have to play with are the parameters.If we could only get back to basic refrigeration and dump all the electronics,we might get somewhere.

[US Iceman]

Hi Chunk,



After the 10 minute drain down,the suction temperature has to reach -10*c before fans start,so in theory the coil should be freezing,but i am getting small droplets of water being sucked out.


Well I think we are getting down to the root cause of the problem anyway. -10°C should be cold enough for the coil to refreeze the water droplets back onto the coil. However, are the coils actually reaching this temperature before the 10 minutes has expired?

If the time duration elapses before the coil is cold enough, then this points to other issues such as...why doesn't the coil get cold enough to refreeze the water in 10 minutes?

If the water is not refreezing, then it will get sucked out into the air stream when the fans start, which is what your problem is. The heater band on the air nozzle is patch to an underlying problem.

[Chunk]

It drips for 10 minutes,then starts to refrigerate after this period until suction temp reaches -10 then the fans start.

As i said in one of my other posts,this isnt just happening on one or two of these units,it is a lot of them.

The older units that these new ones replaced,never had this problem,they use the existing electronics and the coldstore itself has never been modified.

I shall have a look into suction/fan start temperature settings to see if they can be lowered even more.

Thanks for your interest.

[Grizzly]

It drips for 10 minutes,then starts to refrigerate after this period until suction temp reaches -10 then the fans start.

As i said in one of my other posts,this isnt just happening on one or two of these units,it is a lot of them.

The older units that these new ones replaced,never had this problem,they use the existing electronics and the coldstore itself has never been modified.

I shall have a look into suction/fan start temperature settings to see if they can be lowered even more.

Thanks for your interest.

Sadly based on what you have said you can't even put a offset in the defrost temp probe,
Because it's suction tempcontrolled.
Is there any way you can increase the defrost temp (Electric or hot gas?) or duration to boil off more water prior to restart.
Or have I missed something?
Cheers Grizzly

[US Iceman]

These defrost issues can be a pain to analyze.:(

Something is causing this system to kick back into refrigeration with fans on before the coil is ready. Where is the suction temp probe located? If it reaches -10°C before the coil actually cools down the water could still be liquid.

I'm afraid an increase in defrost time would cause the coils to start steaming which pushes the water back into the atmosphere to again refreeze on the coil.

There has to be something wrong with the suct temp probe location or the settings on the controller. Is the timer adjustable for the drip and drain settings? I don't think the temperature needs to be lowered.

It seems to me it's either the probe location or the time values need to be increased either on the drip or drain times (which I would still like to see a factory sheet on).

[coolhibby1875]

hi guys i have this same problem also in sainsburys sites but only in radford sites all the ones with elm controlls seem to be fine

[NIKK38]

I get the same problem on units fitted with Carel and RDM controllers. I've removed the inner cowl and just left the grill/fan guard in place.

[Chunk]

I think i found it.

After defrost,when blower is on drain down,the pan heater is on.The controller then shuts off the pan heater and goes straight into injection mode to bring suction temperature down to -10.

I timed this action and wanted to see properly, if as Iceman says,the water left on the evap was not freezing and being sucked out.

From when pan heater goes off,to when suction/evap temp reaches -10 it took roughly 30 seconds until the fans cut in.

The water i could see coming out was not from evap coil,but from water in the drip tray.

The problem is then that,there is no offset in the controller to shut down pan heater earlier,it literally goes off and 30 seconds later the fans come back on,so there is still some water that didnt make it to the drain.

Just to make sure,i popped to another site and tried this out,and that one does exactly the same.

As Coolhibby says,this is only on Radford control units.

The other thing i found is that this problem seems to be worse on blowers fitted with txv`s.The other ones that seem to be a little happier are the ones fitted with electronic valves,and these take longer to reach the -10*c to bring fans back on.

I`m going to have a word with some-one at Radfords tomorrow.

[US Iceman]

So it would appear to be a controller issue rather than an actual evaporator problem...

Now for the big question.

Do all of the evaporators that have this problem use the same type of controller?

And, at those locations where the problem does not exist with the evaporators do they use a different controller?

[US Iceman]

Another idea for consideration...

If all of those problem locations are using the same controller management should be informed of the issue so that they have some feedback on the decisions made. Particulary the one to use that controller.

It's either a limitation of the controller or a problem with the definition of what the settings mean.

[US Iceman]

...when suction/evap temp reaches -10 it took roughly 30 seconds until the fans cut in.


Some part of the evaporator is reaching -10°C quickly and causing the fans to kick in. 30 seconds is not enough time for the water to refreeze.

Where is that sensor/probe located on the coil?

[Chunk]

So it would appear to be a controller issue rather than an actual evaporator problem...

Now for the big question.

Do all of the evaporators that have this problem use the same type of controller?

And, at those locations where the problem does not exist with the evaporators do they use a different controller?

It seems that yes they all have the same manufacturer,but i have a couple of different versions.On our recent refits they had upgrades to the newer controllers.

[Chunk]

Where is that sensor/probe located on the coil?

The temperature probe is sited about 3/4 of the way down the evaporator or about 2" before it goes out of the blower.

[Chunk]

Thinking about it,now these units have txv`s the only reason they have suction probes is to switch the fans back on as the controllers do not need to control the superheat anymore.

It has got to be a controller issue rather than refrigeration as i am sure a lot of people would have made a fuss before now.

I dont want to get a recall on these controllers as they are already changing a couple of thousand others due to them setting the shops alight.They probably wont listen to me anyway.

[US Iceman]

The temperature probe is sited about 3/4 of the way down the evaporator or about 2" before it goes out of the blower.


Are the probes installed on the return bends or the fins?

The fins will take longer to cool down than the evaporator tubes, and the bottom of the return bends will be colder than the top of the return bends.

If this probe is field installed rather than factory installed, you might be able to locate the probe on the top of the suction line coming out of the coil. You don;t want to sense liquid temperature, you want the gas temperature (heat transfer is slower through gas than liquid).

I guess what I'm saying right now is; there might be a way out of this (between modified controller settings and probe locations).

A cut sheet on the controller is what we need...

[coolhibby1875]

hi chuck i would site my suction probe about 3 inches back form the equalising this should hold your fans off a wee tad longer.
how are you getting on down there with parasense up here we took over 150 alarms from friday through to monday?

[Chunk]

I shall have a go at moving the probe.

I have enclosed a file on this controller.It does not give you any settings as you are supposed to make them up yourself.Nice.

[Chunk]

how are you getting on down there with parasense up here we took over 150 alarms from friday through to monday?

Hi

It s all nuisance alarms.We are lucky really that we have people in the office who dont really care and close 80% of calls without even looking.Cant wait for it to start snowing again.

[philfridge]

Hi have you tryed fitting the kdsl 40w heater tapes around the fan rim inside the guard and wired them in permanent ? Also I think the defrost termination could be lowered to say 10c maybe.

[US Iceman]

I`m going to have a word with some-one at Radfords tomorrow.


I think this is wise course of action at this point. I looked at that sheet you posted and it does not explain very much in the way of controller operation or capability.

[Chunk]

Controllers are fine,spoke to a couple of other people about it,and they are having the same problems and just give the fans a tap every few days.

I have moved the probes about and will monitor what happens,i dont think i`ll be getting anywhere fast with a solution.

Many thanks for your suggestions everyone."If" i find a solution i will let everyone know.

Stay cool.:cool:

[US Iceman]

Chunk, you might try disconnecting the fans manually during defrost. Then when the coil goes back into cooling, wait for 5 minutes or so and then reconnect the fans.

My guess is the fans won't pull off water then. If this works, then you have a pretty good idea the controller is not adjusted right, or something is causing it to turn the fans on prematurely.

[Chunk]

Chunk, you might try disconnecting the fans manually during defrost. Then when the coil goes back into cooling, wait for 5 minutes or so and then reconnect the fans.

My guess is the fans won't pull off water then. If this works, then you have a pretty good idea the controller is not adjusted right, or something is causing it to turn the fans on prematurely.

Hi

I went through controller with a "decent Radford engineer" and we both concluded that the controller is working fine and does what it is being told to do.

We moved the probe out of the blower and put it on the main suction going out of the coldstore and changed a few settings.This gave the coil more time to flood(nearly 4 minutes until fans came on)and i am going back to check operation on friday.

The other thing we found was,when these coldstores are comissioned,they are set up identically but each one behaves differently.So what i do to this one,may not be good for another.

[750 Valve]

chunk you mentioned the pan heater was on during the 10 min drain down, this is something that we pretty much never see here. Is it possible to cycle the pan heater off with the def heaters, it is pretty unlikely that the pan will get back down below zero degrees in the drip time (and if it does it won't have a chance to freeze massive amounts of water in it) from the room air temp being cold still. That way when the coil floods on fan delay there is no heat affecting the refreezing of droplets at the bottom of the coil. We normally run the pan heater along with the coil heaters and usually on the same circuit, we pretty much treat it just like a defrost heater.

Do the probes have a stainless bullet casing? Or are they more like a good old bare thermocouple? Without that casing they will react VERY quickly to temp deviations which may account for the very quick fan delay tat you are seeing.

Is there an option to start fans on time delay not temp (this is personally my preferred option)

Also considering the SST of the system would be somewhere in the -25C vacinity you can still lower the fan cut in setting a little and not floodback (assuming you have a rack/pack setup with a decent piperun) say to -15C which will allow a little more than 30 seconds fan delay.

Just another though too, is your coil out/fan delay sensor sitting close to the distributor and being affected by the chilled distributor - its a long shot but I've come across it before thats all - coil out probe had a distributor leg sitting about 4-5mm above it and the coild was affecting the coil out probe.

[Chunk]

Hi 750 Valve

The pan heater is on a seperate circuit and is controlled by drain down time only.It can be wired in with other heaters.If all else fails i might try it.

The probes are encased and i have insulated them(apart from air on/off)so they shouldnt be affected by other parts of the system.

The controller only starts the fans on temperature and has no facilities to change this.

I have dropped the fans start temp to -15*c on one blower,and on the other i have moved the suction probe out of the blower,about 12" on the main suction.

I pulled a sickie today(spending too much time in this poxy freezer),so am going back tomorrow to check if anything worked.

[IceMan08]

Hi

It s all nuisance alarms.We are lucky really that we have people in the office who dont really care and close 80% of calls without even looking.Cant wait for it to start snowing again.
Yeah Tims good like that :cool:
Although I must say im glad I got out before parasense is rolled out across all the sites-feel sorry for anyone on call, especially when its 3am, you drive an hour just to close a coldstore door that nightshift are working in!!!:)

[750 Valve]

Yeah Tims good like that :cool:
Although I must say im glad I got out before parasense is rolled out across all the sites-feel sorry for anyone on call, especially when its 3am, you drive an hour just to close a coldstore door that nightshift are working in!!!:)

nothing wrong with that mate, it$ all about taking the good with the bad and the ca$h that come$ with it... look at it a$ money for nothing, $mile and get your docket $igned

[Pykester1]

This is not just a problem with one type of unit as we have various models.

The defrost settings i have used are as follows:

Fans off in defrost
Evap temp to end defrost 20*c
Drain down time 10 minutes
Suction temp to turn fans on -10*c
Defrost duration 20 minutes.

The rims are the only place that ice forms,i have no ice on front or inside unit and i have no water running down from the roof.
Hello Chunk. In my experience, looking at your settins I would suggest 2 things. 1. Your def term may be too high, and 2. Your drain down time may be too long.
Defrost heaters will continue to produce heat and steam in the coil long after their power has been turned off. If you already have a high term temp and then you allow them to stay warm for another 10 minutes for drain down, you may be producing a lot of steam which will precipitate on any cold surface near the coil. This will then freeze and if it is on the fan cowl it will jam the blade. Try checking the position of the defrost term sensor and making sure the coil isn't getting too warm during defrost. I recommend 10/12 degrees. Then lower your drain down time to 2 minutes or even nothing at all. Remember you need the minimum amount of heat to clear the coil, then you need compressor back on. You may also want to reduce your fan delay time/temp.
Hope this helps.

[Chunk]

Hello peeps,i`ve been working hard so disappeared for a bit.haha.

I have been playing with the settings and found a happy medium which seems to have been working ok.

Basically i shortened defrost times,termination temps and drain down time,so defrost length 20 min,termination temp(evap temp)10*c and drain down 2 minutes.Also fan start temperature i changed to -15*c(this is for evaporators with heaters,the sat-gas evaps are set slightly different.)

I removed the heaters that i fitted around the rims as they were causing condensation on the front plate.

It just goes to show that just throwing these units in and not taking the time to set them up properly causes more work in the long run.

Thanks to everyone who replied,you`ve been a great help.

[US Iceman]

Hey Chunk,

Without going back through all of the posts I seem to remember you said the frost/ice was forming on the top of fan cowl (and maybe the bottom?)...

Usually when you see the ice forming like this it is because the steam off of the coil is warm and rises. So, it floats out of the coil in the path of least resistance, i.e., the front fan cowling.

That's usually an indication that the defrost is on too long.

I don't know what made think of this now, but since it's free advice it didn't cost you anything.:)

[Chunk]

Thanks USIceman

I think your first post said that the problem was probably the defrost was on too long.

its a common problem in most supermarkets,that when these coldstores are first commissioned they just set the coldstore temperature and defrost times and walk away(they do in mine).90% of the time we leave these problems or do a temporary fix,but i just wanted to try and work out a solution without spending money and it was something simple to do with setpoints.

Thanks again.

[Saudulla Waheed]

are these the old style ones with the round blue baffles as we had probs with these due to long/hot defrosts causing moisture from roof to run down onto gaurds/fan blades and jam fans,it sometimes caused the capacitors to heat up and fail.hope this is of use
no Idea buddy....

[nike123]

no Idea buddy....


Hi Saudulla! Welcome to RE!

I must say, interesting first post.:D
If you keep with this practice, you will very soon be one of top posters.:rolleyes: