Freezing back to comp (mitsu elec)

[expat]

Hi everyone,
I picked-up a maintenance contract on four mitsubishi electric units a few months back. Did the usual: visual inspection, leak test, wiring in good condition, condensate evacuation, clean filters,... etc.

Day before yesterday I get the call. Two units are not cooling properly. Of coarse, when I get there everything is OK except on one indoor unit I found the air on 26°c and air off 6°c. Outside I found icing on the return pipe.

Back inside I had a look, as best I could, with a torch at the fan blades that, were visible, and saw them to be encrusted with dust.

Both indoor units had to come apart to remove the fan turbines which were both very heavily soiled. Now they took some time to clean and when they went back in all was as should be: LP came back up so no more icing and room temps came down nicely.

These things only run in summer so how did they get so clogged up. I thought the filters were there to stop this or perhaps they are but maybe the last people who had the maintenance contract weren't cleaning them.

Does anyone have an idea of a product we could spray these blades with (once they are clean) that would stop dust getting an initial hold, like polish or wax or something.

It's just a thought as It was rather a time consuming job.

[charlie]

Have a look to the zep industries web site (there is one for France too) the product you are looking for is the "Foaming Coil Cleaner".

[Gary]

Hi everyone,
I picked-up a maintenance contract on four mitsubishi electric units a few months back. Did the usual: visual inspection, leak test, wiring in good condition, condensate evacuation, clean filters,... etc.

Day before yesterday I get the call. Two units are not cooling properly. Of coarse, when I get there everything is OK except on one indoor unit I found the air on 26°c and air off 6°c. Outside I found icing on the return pipe.


You might want to consider adding 'air on/air off temps' to your "usual" inspection procedure.

[The Viking]

Have a look to the zep industries web site (there is one for France too) the product you are looking for is the "Foaming Coil Cleaner".

Isn't this the cleaner that's really corrosive and need to be well rinsed after use? Also if we are talking about the same cleaner then it's for condensors only.

[expat]

Gary you are of course right as you would be (after all you did write the book) and I would have to add that I didn't immediately notice this problem several months ago when doing the inspection because I acted like a complete novice and started by hooking up the gages instead of using common sense and the other five senses.

I've often read with interest your posts where you stated the importance of air flow and I could not believe that it would make such a difference with only a minor restriction. I mean I could feel air flowing on fan full speed but it felt more like low speed.

I still find it surprising that so much muck was able to get through those tiny spaces between the fins of the evaporator and adhere to the fan.

Oh Viking, I don't think Charlie gets my point here as I'm looking for a preventative cure but hey if anyone can think of an easier way of cleaning them rather than completely dismantling I'm all ears.

Good to hear from you all.

[paul_h]

Keep the filters clean and it won't be a problem. I've seen three year old units with clogged up fans and drains because they don't keep the filters clean.
I've seen 8 year old units with perfect fans and never have a drain blockage because they keep the filters clean.
If the filters get restricive all the dust and dirt just bypasses them through small gaps and ends up in the drain and on the fan.

[charlie]

Viking,

You are right I haven't read carefully the message, my fault.

From what I know the product is specific for split and fan coils (so indoor coils) and defnitively isn't aggressive for the aluminium fins.

[fridge doctor]

Recently had a call to a unit in a small computer server room, just a 9000btu wallsplit unit but more than capable since all surrounding areas were well covered with cassettes. Several guys had been in and said everything OK. So this is a challenge right ?
Temperature check revealed that the air off was reading the same (more or less) as the air on ! Pull the system apart to reveal heavily encrusted airwheel fan blade. Filters were clean and building only 4 years old, but previous engineers had obviously cleaned filters but ignored main problem. Cleaned all grunge from fan, washed coil and airways and air off temp dropped by 12 deg. Amazing... So simple but VERY IMPORTANT.

[Brian_UK]

<->I still find it surprising that so much muck was able to get through those tiny spaces between the fins of the evaporator and adhere to the fan.<->.Unless I'm mistaken the air passes through the filter then the fan blows it out through the coil.;)

As has been said above, a clean filter is the most important part of the system. This assumes before the filter is removed for cleaning that the fan has been turned off.

The number of times I have seen blocked filter pulled out of a unit with the fan running is scary.

In a normally running unit some of the dust will pass through or around the filter. Providing there is some condensate being produced then, with luck, the dust will run off into the drain tray and get pumped away.

If the dust is allowed to get too heavy then whenever the unit stops producing moisture (off period) but the dust is still being drawn in and will start to collect on the outlet of the coil.

This little collection of dried dirt will slowly buildup like a small dam on the fins and as the airflow reduces then more dust can settle out.

If the units are heat pumps then a quick run in heat mode and the use of your nose can indicate potential blockage problems.

If it smells rank then there is muck on the coil which is getting cooked with the higher temperatures.

[Makeit go Right]

I've seen a 6-month old 5kW system with caked up fan scroll. The filter did its best, then the dirt got around the filter, filled the coil and caked onto the fan impellor blades. The convenience store manager liked to leave the front door open and the speeding traffic outside created lots of dust, which found its way into the open store and was then drawn into the unit.

The manager, who insisted on doing his own filter cleaning with just an annual service from us, was shown how to clean the filters and told to check every 2 weeks. But he had done nothing until the unit duty dropped off. Then he opened the front and hoovered the filters in situ, and then called us to complain about poor performance of the unit (under warranty).

The fan impellors were rotating nicely but they were so clogged that the curved blades were just like round rods, with no affect on moving the air through the unit.

The filters were clean in the middle (where he had hoovered) and completely choc-a-block at the edges. "Exibit-A." Well, the unit needed major surgery to clean it up properly, and the manager paid the repair bill.

I called in 3 weeks later and checked that he was cleaning it correctly - he was.

Six-month intevals and even 3-month intevals are sometimes not frequent enough, like in the above example. So, if you have an open door or otherwise dirty environment, be sure to show the customer how to clean the filters and tell him/her to clean frequently until the correct frequency is evident. That way s/he cannot say "Well I didn't know they needed cleaning so often."

[monkey spanners]

Might be mold or fungus growing on the fan. can appear in no time.
I'd wash a dirty fan etc with Condenside by Advanced engineering or Envirocoil by the same company.
Used to look after a night club and coil cleaner was the only way to get the sticky mess off the filters. After a few callouts to blocked filters the barman took to puting the filters in the glass washer:eek:
"no i don't want a drink thank you"

Jon

[expat]

paul_h

Keep the filters clean and it won't be a problem

Thats pretty much what I thought, thanks mate

fridge doctor

So simple but VERY IMPORTANT

You're right, the obvious is often right there staring us in the face!

Brian_UK

Unless I'm mistaken the air passes through the filter then the fan blows it out through the coil.;)

I'm not sure I follow..., I feel the air is drawn through the filter, then through the coil and then out into the room.
The rest of your reply has some interesting points I hadn't thought of.
Thanks Brian.

monkey spanners

Might be mold or fungus growing on the fan

Now you're just being scary.
The grunge was pitch black with, in places white fringes, like mould formation.
This was in an analytical laboratorie!
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I think I've caught Ebola:eek:

[expat]

Quote Black Adder:

"I would shake your hand, but I fear it might fall off."

[paul_h]

If its a mould like substance I would flush the hell out of the drainpan with bleach and hot water, and check the drain outlet to make sure it's clear and flowing freely.

[Brian_UK]

Brian_UK

Unless I'm mistaken the air passes through the filter then the fan blows it out through the coil.;)

I'm not sure I follow..., I feel the air is drawn through the filter, then through the coil and then out into the room.
Sorry Expat, I was thinking of cassette units but you perhaps have void units or similar.

I'll go sit in the corner for a while:)