Stopping the Mitsubishi PEFY fan

[jbreiden]

I'm a homeowner, and just had a Mitsubishi City Multi system installed. It is awesome except that the indoor air handler fan never stops. And that's a problem at night.

The house has four zones. One of them is for bedrooms and uses a PEFY ducted air handler. On a cold winter night the bedrooms receives warm air, then cold air, then warm air, then cold air, etc. Cold means 10C because the return is in a hallway that we don't heat at night and the ducts run through an unconditioned crawlspace. There is a remote temperature sensor in the master bedroom.

Our contractor talked to Mitsubishi and was told (1) The fan will continue to operate, for a period of time, after the temperature is reached. This is by design to provide better heat circulation to the conditioned area. (2) There is no configuration/settings to immediately stop the fan after the temperature is reached to the pre-set value. This is also true using the temperature sensor inside the PEFY unit.

I wonder if someone knows a super ultra crazy secret trust no-one James Bond-like trick to solve this problem.

PEFY-P18NMAU-E (ducted indoor air handler)
PUMY-P48NHMU (outdoor unit)
TC-24 (central controller)

[Thermatech]

Generally it would be good practice to place the indoor unit in the room or in the case of ducted indoor units the return air to the unit should be from the same room as the supply air.

Mitsubishi indoor units do not have an option for fan off at heating mode set temp.

There are 2 options
1/ fan slows to very low speed when at set point temp heating off. ( factory setting )
2/ fan stays at remote controler fan speed at set point temp heating off.

Thats the way Mitsubishi have made indoor units for the last 18 years that I have been working with City Multi systems.

The indoor fan is electronically speed controlled from the indoor circuit board so there is no way to hot wire the fan motor to stop.

[jbreiden]

Thanks for the quick answer. I guess I'll keep playing with the timer, so that the entire bedroom zone is turned off for hours at a time during the night. This lets temperatures coast down more slowly than when the system is pumping in cold air. It's a little awkward but not too bad. For the record, Daikin and Sanyo systems both have settings that allow that fan to be turned off. Although it is apparently incredibly hard to get hold of those settings.

[Startrek]

If you switch on dip switch sw1-7 and 8 on it will switch the fan off when it reaches set point however you will have to watch where you are sensing the return air temperature as you will have no air flow through the unit.

[jbreiden]

Thank you very much.

[hvacson]

1-1 will change temp sensing to thermostat. you will see a few degree offset but it will work better than seinsing in duct if fans off