Mini-split Achilles heel

[Jackfre]

In a previous post I spoke of how my line set had been cut on my Fujitsu 12 RLS system. I have had this unit installed for 3-4 yrs and it has worked very well. I regularly clean the filters and vacuum the face of the coil. Performance has fallen off over the past year or so. Since the unit is inop. I pulled the evaporator off the wall and was shocked at how dirty the whole unit was. The back of the coil was packed, as well as the face. The fans curved blades were dirty and there was a ridge of dirt at the lip of each blade. I ended up dropping the fan assembly out of the unit as it would be about impossible to effectively clean it otherwise. I bought a sprayer and some NuCalgon green coil cleaner. At this point the evap is clean as can be, but in pieces. In order to clean these in place you will need some heavy plastic sheeting draining into at least a 5 gallon pail. I have 3 more evap in the house and will be cleaning those soon.

If you have followed any of my posts you know that I am a major fan of mini-splits. This doesn't change my opinion. It just changes my service schedule. I called Fujitsu Tech and they said they recommend this cleaning twice a year. Do not overlook this. Once they are packed like this one was I don't think it could be cleaned adequately in place.

 

[CWO4GUNNER]

It is amazing how inside the house these things including CPU fans, ceiling fans, stove duct and bathroom fans and there associated screen's can get so inundated with stuck on oil impregnated dust grim. Personally I use Honeywell air filter to help, nevertheless I still use my ceiling fan as a guide. When the ceiling fan blades edges get a head of dust I know it's time to clean them. Wonder if ddevising a filter screen for those evapes would work?

 

[pseudorealityx]

Yup. No way to properly filter air with a mini-split wall mount. They just don't have the static to deal with a real filter.

 

[bullnerd]

Is there any way to build a pre-filter for one of these?

I have been reading as much as possible about MS's and this seems to be a concern, especially since I'll be doing wood working pretty close to where I planned to mount the inside unit.

Uni-filter, the off road/atv/motorcycle filter company makes some really good filter material in sheets, could a simple cover be made with a replaceable, washable pre-filter in place?

I've never seen a MS in person so hard for me to design something.

 

[CWO4GUNNER]

Perhaps using cassettes with a SS hi-flow screen like they do on window AC would at least help if they could be hidden or a custom soffit made. I suppose with the wall mounted type there in no place to hide a screen without it showing. But its another thing on my list I will have to solve in preparation for my whole house mini-split install. After all there really are no problems, only solutions.

 

[rlitman]

Is there any way to build a pre-filter for one of these?

I wouldn't. If it doesn't come with a washable filter, don't buy it.
Adding anything would reduce airflow, and cause issues.

Every one I've seen has a washable filter, and collects no more dirt than a window A/C. Probably a little less, since the intake is way up by the ceiling (which has less "big" dirt in the air such as floating hairs).

I clean my interior unit at least once a year. Foaming self-rinsing coil cleaner is what you need, after vacuuming anything that has collected on the surface of the coil. Turn the unit ON, and use the fan to **** the foam into the coil.
Then finish up by cleaning the vanes with a baby wipe.

If you cool more than I do (I do not use it all the time), then cleaning twice a year is a good idea. Keep up with the cleaning, and it doesn't get that bad.

 

[bullnerd]

Perhaps using cassettes with a SS hi-flow screen like they do on window AC would at least help if they could be hidden or a custom soffit made. I suppose with the wall mounted type there in no place to hide a screen without it showing. But its another thing on my list I will have to solve in preparation for my whole house mini-split install. After all there really are no problems, only solutions.

I wouldn't really care what it looks like, as long as it works and protects the guts.

I wouldn't. If it doesn't come with a washable filter, don't buy it.
Adding anything would reduce airflow, and cause issues.

Every one I've seen has a washable filter, and collects no more dirt than a window A/C. Probably a little less, since the intake is way up by the ceiling (which has less "big" dirt in the air such as floating hairs).

I clean my interior unit at least once a year. Foaming self-rinsing coil cleaner is what you need, after vacuuming anything that has collected on the surface of the coil. Turn the unit ON, and use the fan to **** the foam into the coil.
Then finish up by cleaning the vanes with a baby wipe.

If you cool more than I do (I do not use it all the time), then cleaning twice a year is a good idea. Keep up with the cleaning, and it doesn't get that bad.

The Uni material is supposed to not reduce airflow by much. It sounds like it is a bigger problem then you make it seem? Is there other openings where the dirt/dust gets in? Like the OP is talking about.

 

[rlitman]

He didn't describe any other openings where dirt would get in. Just the fact that the inside was packed with dirt.

Having dirt accumulate on the fan blades is not surprising, but also probably not an actual problem. Dirt packing up on the coil in a way that obstructs airflow is a problem.

The washable filters that come with most of these units restrict airflow about as much as a window screen. They're really not made to handle more than that, and I would expect not only to cause mechanical issues due to reduced airflow, but also potentially a higher collection of dirt, due to reduced velocities.

Good cleaners break up what holds the dirt together, and lets it self-wash out in the condensate. Oh, and toss a mint in the pan when you're done cleaning (you don't want algae clogging the drain).

 

[bullnerd]

He didn't describe any other openings where dirt would get in. Just the fact that the inside was packed with dirt.

Having dirt accumulate on the fan blades is not surprising, but also probably not an actual problem. Dirt packing up on the coil in a way that obstructs airflow is a problem.

The washable filters that come with most of these units restrict airflow about as much as a window screen. They're really not made to handle more than that, and I would expect not only to cause mechanical issues due to reduced airflow, but also potentially a higher collection of dirt, due to reduced velocities.

Good cleaners break up what holds the dirt together, and lets it self-wash out in the condensate. Oh, and toss a mint in the pan when you're done cleaning (you don't want algae clogging the drain).

Sounds livable.

 

[Jackfre]

Pre-filters will not work. As Pseudo said the units are designed with a very low static pressure capability to keep them quiet. Any additional resistance to flow will only reduce performance. In a wood shop I'd run an ambient filter. I ran a JDS 200 filter box in my wood shop and it was a big help. Make sure you understand how to break the unit down before it is on the wall. Every system has a personality. You will get to know yours, but I think you will end up cleaning it up frequently.

NuCalgon makes a mini-split evap cleaning kit, which is basically a large paint size spray can of coil cleaner. I bought a pressure sprayer and a gallon of the same cleaner for mine, but I will have to do my other 3...and damn it, probably friends too, Oh and the daughters. Hmmm, anyone I'm missing?

 

[bullnerd]

Sounds good. Definitely an air filter and a dust collector.

I was just nervous periodic cleaning/maintenance wasn't enough.

Thanks for the info.