Midea Headaches

[TrickyRikki]

Afternoon all,

Has anyone got any ideas on this issue, I was called to a multisplit midea unit the other day with reports of the units not working in heat and constantly in defrost.

The office was at 18 in the morning and they set the unit to 23, when I arrived (late afternoon) the room was only at 19.

No faults and no errors on indoor or outdoor, run unit in forced cooling and the pressures were
L-7bar and H-10bar cooling fine, when switching to heating both pressures at 30bar, my initial thought was 4 port valve not sliding over properly, I tested the temps on the valve and going by the temps recorded the valve seems to of fully changed over.
Tested the 4 port valve with a magnet and it seems to work but I'm concerned with the equal high pressures when on heat.

Technical were stumped too.

[seanf]

What refrigerant?
Where are you taking the pressure readings from?
What type of expansion device(s) does it have? For cooling mode and for heating mode. Sorry never looked at Midea stuff before.

Its not just a restriction on the expansion device (strainer/check valve if there) used for the heating mode? That could give you HP at the access valves on the shut off valves where you pipe up the outdoor unit. And give too low a temp at the condenser, assuming its defrosting based on a thermistor reading.

[TrickyRikki]

What refrigerant?
Where are you taking the pressure readings from?
What type of expansion device(s) does it have? For cooling mode and for heating mode. Sorry never looked at Midea stuff before.

Its not just a restriction on the expansion device (strainer/check valve if there) used for the heating mode? That could give you HP at the access valves on the shut off valves where you pipe up the outdoor unit. And give too low a temp at the condenser, assuming its defrosting based on a thermistor reading.

Sorry, I was in a rush yesterday posting this.

Gas is 410a.
Unfortunately the only place I can gauge up is the shut off valves where the pipe is connected.
It has an EEV inside the condenser for cooling, heating not too sure, I'm not too familiar with the unit either.

[Peter_1]

Coolin and 7 bar LP and 10 bar HP and that's OK ? No, this isn't ..

[TrickyRikki]

Coolin and 7 bar LP and 10 bar HP and that's OK ? No, this isn't ..

Never said it was okay. I said it was cooling fine, it's the 30bar equal pressures that concerned me more

[seanf]

Sorry, I was in a rush yesterday posting this.

Gas is 410a.
Unfortunately the only place I can gauge up is the shut off valves where the pipe is connected.
It has an EEV inside the condenser for cooling, heating not too sure, I'm not too familiar with the unit either.

Maybe theres more than one restriction.
Do Midea units give you a pressure transducer reading you could use for the suction?
I guess just look for the point where its frosting up. See if Technical can send you a P&ID.

[TrickyRikki]

Maybe theres more than one restriction.
Do Midea units give you a pressure transducer reading you could use for the suction?
I guess just look for the point where its frosting up. See if Technical can send you a P&ID.

There is a small led tube display (the 2 8's that light up) after looking in the technical manual it does state you can read the values but when I tried to swap what it was showing me it wouldn't, I spoke with technical and they was meant to be getting back to me on how to do it but as of yet no response.

I will be back in that area next week so will go look for frosting ect

[martinw58]

10 bar head pressure is very low for 410a have you checked the gas charge