Jet Engines in My Living Room

jimolson52

I have a new 2.5 ton ducted Mitsubishi H2I system of the SUZ- variety to replace an older Goodman ducted system.

I bought it because the new identical H2I system at my church did indeed work down to 5 degrees as advertised without the back up resistive heat kit. I know this because I flipped off the breaker to the heat kit as a test of the system's cold temp performance.

Regarding my new home system, I was accustomed to hearing refrigerant flow in the copper line set of my old Goodman system, especially when the changeover valve flipped. But this Mitsu system's refrigerant flow in the copper sounds like a jet turbine firing up for the first time.

And at today's 38 degrees OAT the refrigerant flow stops and starts continuously about 2 times per minute.

I guess I thought the Mitsu's variable speed compressor would find a happy mid-range RPM and remain there to maintain the thermostat's set point. But what it's doing is duty-cycling the compressor on and off between zero and full RPMs a couple of times per minute, though it's ramping it up and down slowly.

I think the variable speed inverter drive on the compressor is simply being used to soften the impact of turning the compressor on so frequently.

Is this system running as it should?

Thanks from Indianapolis.

GGross

How was the system sized?

Was this installed by a licensed pro or DIY?

pecmsg

how was the equipment sized?

how are the ducts sized?

if you can hear the airflow, that’s a sign of on undersized ducts

jimolson52

GGross, the system was sized by the license contractor that installed it. He's probably selling more Mitsu H2I systems in this region than any other contractor. His 2.5 ton estimate is the same as the original developer's when he built the 200 condos in this complex. All have 2.5T units.

The noise isn't from the blower or the ducts. It's from the refrigerant flow in the copper line set in the living room wall. In fact, the blower speed is amazingly low compared to the old tech system he ripped out.

The slow blower speed is what allows me to hear the refrigerant moving in the copper line set.

GGross

Are you able to trace back the lineset at all to be sure it isn't vibration noise? You can sometimes hear some noise from the linesets but what you describe seems excessive to me. I would say the installer should come back and observe this, I would wager something is off with the charge or something else is happening within the refrigerant system. there could also be some vibration that adds to the sound but if you hear it flowing through it can't be just vibration

jimolson52

Good advice, GGross.

I think what surprised me most was the unusual control strategy, not so much the noise the system emits. If this Mitsu unit played Hotel California at high volume it would still be quieter than the Goodman system he ripped out.

It's quite possible the Mitsu system will stop duty-cycling the compressor when the weather brings greater heating or cooling loads.

Otherwise I'm entirely pleased with my purchase and the contractor's performance.