mitsubishi electric a/c

[bellaman]

hi guys i have a problem with a mitsubishi electric a/c system in a store in a shopping centre i can get 40 degrees off coil on heating and on cooling i am only getting 20 there are 3 indoor cassettes and 1 outdoor unit and it has water heat exchanger i checked all the pressures and they are all ok i would be verry greatful for any help on this.

thanks

[Peter_1]

What were your pressures and even more important, your temperatures?
40 degrees, almost burning hot I should say.
Types of the units?
Heatpump, on/off, inverter,....

Too less information to help you

Water heat exchanger, where installed, how's this controlled, what temperatures of the water and is this a standard Mitsubsihi feature?

[Thermatech]

WR2 outdoor with BC distribution box & 3 large indoor units.

You have poor refrigerant flow through the indoor units resulting in poor off coil temp.
How long did you leave system heating ? If you only gave it a short heating test then the indoor coils can fill up with hot gas & produce good off coil temp for a few mins but then then hot gas condenses out to liquid if poor refrigerant flow through unit & off coil temp falls away. In this case you could suspect the indoor unit LEV valve locked shut.

If poor performance at all indoor units only in cooling mode then make sure system is not SOG & then see if there is any liquid to suction bypass at the BC box.

LEV 3 at the BC box is a prime suspect as it needs to be fully open when all units are in heat mode to allow full flow of liquid to flash off back into the suction & back to outdoor unit.
If it has failed & is locked wide open then when all indoor units are cooling you have liquid to suction bypass at the box & very poor or no liquid flow through the indoor units.
Outdoor units sees cold suction temp & ramps comp down to slow speed.

Make sure you have good water flow & temperature on the outdoor coil.

If you still have dificulty please give more detailed data.

[Peter_1]

WR2 outdoor with BC distribution box & 3 large indoor units.
.
I know the Mitsu's very well but he didn't say that he's using a WR2 unit. Why can't it be a WY Unit without BC controllers?

[Thermatech]

I know

I made a guess at PQRY WR2 system because engineer told us good heating performance but no cooling & acceptable pressures.
Classic BC box LEV 3 liquid to suction bypass symtoms.

Idealy more information needed to provide any help without guessing.

[Peter_1]

Idealy more information needed to provide any help without guessing.

That was what I was trying to say: most technicians don't look hard enough and haven't measured the needed values to diagnose properly any AC or Refr. system.

We need a lot more information before we can help.

The fact that they - without pointing specific to the original poster - don't give us the proper information learns us that they don't know excatly what to look for.

But thats why this forum and the www is so great and helpfully, you can learn in much bigger steps then we did without making the errors we made in the past.

[bellaman]

thanks for all the replys we will be going back soon and i will try and get more info