Mitsubishi concealed SEZ-KA35VA not cooling when door is shut closed.

[madmax80]

Hi,

We have a power multi system at home. For one of the bedrooms, 12 square meters, we use a SEZ-KA35VA bulkhead, which is located in the corridor's ceiling facing to the room just above the room's door . Above the room door we have a linear diffuser grille used for distributing from its upper part and return air from the bottom part. the blades have a 15 degrees diversion facing downwards.

1. When the door is shut, it seems like the air conditioner stops cooling.
2. It starts to make a foul smell
3. The door is pushed towards the doorpost
4. I'm thinking the pressure in the room is raising.
5. When standing just next to the door from the inside of the room, I can feel the wind on my head.

Generally, it seems like the indoor unit doesnt circulate the air well.
Any ideas what can be causing this? The grille was increased and is huge now.. so I dont think that is the issue.

[Brian_UK]

Sounds like a return air problem.

You say the the lower section of the grille is for the return air, can you check that air is, in fact, moving through the grille?

[madmax80]

Thanks Brian.

If I put a toilet paper close to the lower area of the grille you can see it sticks to grille, so I assume the air is moving towards the unit. Does that sound right?

Any chance it's something with the unit itself?
I'm lost.

[niceman]

The grille you held the paper up to has a removeable, washable filter behind it, you should see 2 lugs on one side of that grille which if you slide to the centre of grille will let the grille fall to you, usually hinged on side opposite the lugs.It is advisable to clean filters regularly. Would advise you to do this with the fan off for your safety.

[madmax80]

Thanks niceman.
The grille doesnt have a filter. the unit itself has a filter and it is totally clean. The unit's air inlet btw is from the bottom not the back if that helps.

[Gary]

If I understand you correctly, the supply is in the room while the return is in the corridor. Is that correct? And when you close the door between, the room is pressurized? Kinda like blowing into a bottle, the air has nowhere to go so it stops moving.

[madmax80]

Thanks Gary.
No, both supply and return air are inside the room and are on the same grille. the grille was split so that its upper part is used for supply and it's lower part is used for return air.

I'm trying to think whether something is clogged or the fans are not spinning fast enough. can that explain things?

[madmax80]

As soon as I open the service door in the corridor, and leave the room's door open, it works amazing. I can fill that the air is thrown strong forward, whereas when the door is shut, the air just falls close to the door. So the unit is OK, but something in the airflow isn't. I have attached images of the grille.
20160718_101914_resized.jpg20160718_101929_resized.jpg

[Brian_UK]

I would therefore suggest that the return air path from the grille back to the unit is blocked off.

Can you see the grille from the access panel? If not then there is the problem.

[madmax80]

Yeah, I can see the grille from the access panel, it's not blocked. but the blades have some sort of deflection, by design.

[Brian_UK]

The plot thickens.......

[madmax80]

what do you mean?

[Brian_UK]

what do you mean?

We're running out of easy answers.

The fact that the air flow stops shows that there is a problem with the return air path but sadly we can't see from here.

[redroge]

There must be a return air grille in the ceiling space !

[niceman]

You say you can see " blades" between the access panel and the grille, this must be dampers which if partially closed will affect air flow, try opening the blades ie increasing the gap between blades and this should increase your air flow. Best of luck.

[madmax80]

Thanks. The blades are fixed, no dampers, i cant change it. 20160719_101340.jpg

[Gary]

The return is pulling air from somewhere other than the room (corridor, ceiling, etc.). You will need to figure out where and how.

[madmax80]

Thanks Gary. I verified it and sealed everything it doesnt pull air from outside the room. It doesnt pull air from the room either. further more, when the access panel is shut, the unit barely works - i.e lacks return air.

[redroge]

Can you take a photo of the indoor unit there does,nt seem to be any ductwork between the unit and grille

[madmax80]

There's no ductwork between the unit and the grille for the return air. there's one for the supply.

[Brian_UK]

One thing to check, you said that the air filter is totally clean. I would expect some dirt to have been on the filter element.

Is there any air moving through the filter?
What difference is there with the filter airflow when the room door is open or closed?

[still learning]

So if it blows out thru the large linier grille. At the top and sucks. Back in thru the bottom.
In the ceiling void the cool air. Could sucked. Back into. The. Unit and stop cooling what I could see of you photo from the hatch , which I take is under the unit shows a drain as well.which. My bring smells back in via. Your return air path.
It's quite hard to see what's going on from your photos.
One of the problems of using a. Ceiling void as a open. Expance to pull return air, is. IMHO .
A problem as you get whatever's in the void .
I have a a ducted in my bedroom roofspace and supply blows in via duct work.
And the return air is pulled thru duct work. To a filter box. With a small hatch to access the filter to clean it .

[rnine]

It seems that an easy fix would be to fit a vent of some description in the bedroom door. This would equalise any pressure differential issues at minimal cost, and you still retain your privacy with a closed door.

[madmax80]

Thanks guys.
Experiment I did this morning which seems to solve the issue. Untitled.jpg put a carton between the supply and the return air. everything now works. it seems like it was sucking everything it was throwing.
The grille blades today are all facing down.
So it seems like I need a new grille where the blades for the supply are facing straight whereas the blades for the return air should face down.

[Good^Man]

Glad you have sorted it, but:

"As soon as I open the service door in the corridor, and leave the room's door open, it works amazing."

That is the odd thing.

When you crack the door open is there a flow of air out of the room through the crack, or air entering the room through the crack?

Sounds like some of the air enters the room via the grille and the rest from the corridor,
OR some of the extracted air gets back via the grille and the rest via the corridor.

Might be worth a close look in the bulkhead to see what is going on with the airflow.

Has it always had this problem since new or is it a new installation?
Filter clean?