Correct way or not?

[Skilleg]

I need a bit of help. So I'm on a job site with another technician and he's working on a mini split Mitsubishi unit. He told me that he thinks it's a dirty coil. So I check the split and it's not a 20 degree split. He then sprays water into the outdoor coil and indoor coil with a spray bottle and the supply temp drops. He checked the split right after with the coils still wet. Was that the correct way to do that? Wouldn't the water still on the coil cause the supply to drop? Just out of curiosity.

[jayguy]

Unless the coil is MADE to be wet, then have to wait until it is dry before you can accurately determine most problems.

[timebuilder]

If it's a dirty coil, you clean it and then you let it dry.....and then you can evaluate performance from there, based upon the Mitsubishi test standards.

[Servicetech72]

I would let it dry , Mitsubishi tec support is pretty good, it never hurts to call with questions, God knows i do.

[Bombboy90]

Was it maintenance or service call? What exactly was the split you read? Were the filters and blower wheel clean? And the above posters are right, let it dry even if it’s the evap (yeah yeah I know it’s wet already but it’s not Niagara Falls) and recheck.

[Skilleg]

Was it maintenance or service call? What exactly was the split you read? Were the filters and blower wheel clean? And the above posters are right, let it dry even if it’s the evap (yeah yeah I know it’s wet already but it’s not Niagara Falls) and recheck.

This was a service call. The filters were clean and the blower wheel was slightly dirty but nothing that I believe would cause a problem. I normally allow the coils to dry. But I just started at this company and they wanted me to ride around with another technician for a while and kinda see how he goes about doing his job. I did nothing on the call but check the temperature split. I can't remember the exact reading but I recall getting like 66 f out of the supply. This is a server room by the way. I guess what I wanted to know or understand is that if I left water on the coils and checked the split wouldn't that cause the supply temp to drop and make it seem as if it's cooling better?. I've never checked a unit with wet coils. He saw it drop for a couple of seconds and called it good and then we left.

[Missouri Guy]

If the supply is cooler after wetting the evaporator.. then it's working as an evaporative cooler.
Mini splits generally have a larger split due to lower cfm of air per ton...so 66 supply is bad anyway. Unless it was pretty warm in the server room.
As a side note a wet coil reduces airflow a little making a slightly larger split
Anyway it sounds like the coil wasn't getting below the dew point of the air...when he wet the coil (evaporator)it was using evaporative cooling which increased the split

When he wet the outside coil the unit gained capacity as it was also evaporating water which made the dry bulb temperature simulate the wet bulb temperature of the outside air.