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Community and Q&A

Fujitsu Heat Pump Incompatibility

sfs134 | Posted in Energy Efficiency and Durability on

My HVAC installer recommended a Fujitsu heat pump air handler (AMUG30LMAS) for my new construction house in upstate NY.  We were going to hook up an ERV to the air handler’s return with a Fantech controller so that I had more control over when the ERV operates; the Fantech controller would automatically start the air handler fan if it was off when the ERV was operating.

Turns out the new Fujitsu units are incompatible with all 3rd party systems, and there’s no way to do what I wanted.  The only option they’re giving me is that the ERV will run whenever the air handler is on.  My concern is under ventilation during times when the air handler isn’t running frequently (I’d have to manually turn the fan on myself every time), or over ventilation (energy penalty) when the air handler is running a lot.  I’m disappointed with this situation; any recommendation or perspectives?

This is the second issue after we found out the zoning system they were going to use wouldn’t work with the Fujitsu unit either.  Because of that, I had to go from one 4-ton unit servicing both floors, to two 2.5-ton units, one for each floor (couldn’t get the 2-ton units unfortunately).  I didn’t mind this too much, because I had wanted two separate systems in the first place.  But now with the ERV issue, I’m regretting going with Fujitsu.

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  1. gozags | | #1

    Last bullet point here seems to show that it will interface.. you are really just looking for 'blower only' function right? ERV is on, move air around (w/o heat/cool)?

    Not sure on the Fujitsu side, but if it was Alexa (or other) integrated and you couldn't tie these together otherwise, you could hit the Fantech ERV manually for 30 mins or whatever and do, 'Alexa, run the HVAC blower for 30 mins.'

    Maybe more than you want to deal with - but if something is 'connected', someone has made a way to tie it to other gear..

    1. sfs134 | | #3

      They told me the Fujitsu external interface didn't relate to thermostats, so I'm not sure what they mean by that bullet point. I guess the main problem is that the Fujitsu unit uses a different voltage than everything else, so they can't tie the systems together like they normally do.

  2. Expert Member
    Akos | | #2

    These fully modulating units tend to run the fan 24/7, the speed of the fan is ramped up and down to match the cooling and heating need. The only thing you might want is to add in a paddle flow switch into the main duct to turn off the ERV in case the heat pump is turned off.

    The other option is to grab a UTY-TTRX thermostat interface module for it. This make the unit look like a standard 2 stage heat pump and gives you a G signal to drive the fan directly.

    The Fujitsu thermostat module is actually pretty good if you configure the DIP switches properly. Each stage is essentially the same as having the remote set for the DIP switch configured heating and cooling temperature. Provided this is all adjust and the thermostat is set right, you get pretty close to fully modulating performance out of it.

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