citi multi defrost issue

[tomp]

Having a problem with my citi multi. when the temperature gets colder (below 25) the unit defrosts quite frequently (every25-35 minutes) and the defrosts are quite long (7-18 minutes) my issue is any of the 4 indoor units that are calling for heat it runs:(the fans on low after shutting off briefly regardless of the coil temperature and I am getting 45 degree air temperature coming from the units which cools the room down about 10 degrees during defrost. Obviously I am getting many complaints from guests, I don't think the system was designed to do this but the local and regional reps have no solutions for me can anyone help?

[stufus]

Hi Tomp
First up You can change the defrost start/stop temp on the outdoor board , see attached manual pg44.
SW3-3 and SW3-4
You can also change the defrost prohibit time SW2-8
And the indoor fan can be taken back to ultra low SW1-7 off(indoor board)

https://rapidshare.com/files/2601380314/sh_city_multi_y_r2.pdf

Cheers
Stu

[tomp]

Thanks for the reply, I assume from your response the fans on the indoor units cannot be stopped from blowing the cold air (ultra low is the best we can do) is that correct?

[Zeppers75]

Thanks for the reply, I assume from your response the fans on the indoor units cannot be stopped from blowing the cold air (ultra low is the best we can do) is that correct?

This is correct, fans can only be set to off during thermostat off.

[stufus]

Sorry Tomp been away for a few days , as Zeppers said fan only off during thermo off.
Cheers
Stu

[soleowner]

It is possible to turn off the IDU fan during heat mode if thermally off. See your Mitsubishi Tech Support agent for details on your particular IDU model. But...

SW 3-1 OFF, SW1-7 ON, SW1-8 ON = Fan Stop in Heat Mode

If experiencing low heat or extended defrost, I would double check the application and expected Btu's of the system via Design Tool.

Another check would be the charge. Use Maintenance Tool for verify pressures and temperatures are within range for the given ambient temperature.