Outback PSX-240 efficiency

Constantine Faller

Morning. Not finding anything elsewhere on the forums or on Outback's product materials. Does anyone have any information, even if field experience, on the efficiency rating of the PSX-240 transformer. Best I can tell the 1:1 windings are flipping the phase of the 110 input, then both are combined for the 240 output. My friend is wondering what the loss is so he can compare running mini-splits on 110 vs 220, as well as whether his Trace SW4024 can handle a 20,000 BTU 18 Amp 208/230V unit.

mike95490

Many transformers are in the 95% efficient range.  The mfg's data sheet is the only way to get closer without a lab full of equipment

Ralph Day

Not quantified, but I've been running a Mitsubishi minisplit with an autotransformer for 9 years with no problems.  There is the load of the transformer itself (6 watts on the Killa watt meter) and 20-45 watts when the system is idle.  I only turn the breaker on when heat or cooling is needed.

With utility or generator power available I have  a DPDT switch to select power from either source as required (battery or inverter supplied).

Constantine Faller

Ralph Day said:

Not quantified, but I've been running a Mitsubishi minisplit with an autotransformer for 9 years with no problems.  

Ralph, what size inverter, what size mini split?

Ralph Day

Outback 3648 inverter, 12,000 btu minisplit.  In AC mode the minisplit uses 350 - 550 watts, heating 800 - 1200 watts.  Helps with the heat, does all the AC comfortably.  Primary heat is wood (but don't tell the insurance company...supplemental to them)

Constantine Faller

Thanks Ralph. It sounds like you leave the transformer on for the heating or cooling season.
For those that are manually powering down their transformer more frequently when heating or cooling is not called for, do you pause for the transformer to come up to voltage, no matter how quick that is, and then manually connect the load? It seems like it might not be great if a mini-split is already connected in "on" mode as its line voltage is going from zero to 220; does the soft-start nature of the mini-split's pump lessen the need for concern?
If concern is valid, I would need this delay of the load on/off, as well as shutting on/off the transformer 110v input, to be controlled automatically.  If a contactor with a 220v relay were to be used on the load side, would the coil in the contactor mind the lesser voltage while the transformer powers up? 
Any suggestions on controlling the 110v transformer input, either how to do so or electrical reasons not to do it? Possibly the complexity isn't worth eliminating the parasitic idle power consumption.

mike95490

I'd leave it always ON, the startup inrush for the transformer can't be great for the inverter, unless you are sized just right

Ralph Day

I do manually start the transformer, when the hum is steady (3-4 seconds) I turn on the switch for the mini split (it's on top of the transformer box).  There's a breaker on the box and a heavy 3 foot cord.  I can run the mini off of utility outlet or renewable (house) outlet.  Best of both worlds.  There's also a pilot light on the transformer box.  When the mini is turned on it lights up.  I can see at a glance if the power to the mini is left on when it's not supposed to be.   Pilot light is an old 240v electric stove/oven indicator/status light.  Also one on my submersible well power feed.

Constantine Faller

mike95490 said:

I'd leave it always ON, the startup inrush for the transformer can't be great for the inverter

Mike, do you think the start-up draw is much different from the current and power draw of starting a submersible pump? I know our pump(not a soft-starting) draws down the house when it kicks in, frequently triggering the two battery backups in the offices. My air compressors used to do the same thing until I incorporated a vertically mounted gate-type check valve in the feed tube between the pump and the tank. Gravity and a light spring opens it. Greater air flow once the pump reaches full rpm closes it. I digress. If similar to a conventional HVAC system that cycles 3-5 times an hour, I can see that there would likely be no energy savings by shutting down the transformer between cycles, and possibly even greater energy consumption vs leaving it powered up; in addition to greater wear and tear.

Estragon

FWIW, if I don't start the transformer first, the submersible pump will trip its GFCI breaker.  If I wait until the "boing" start is done, ~2secs, the breaker is fine.  I don't know what's happening during the boing to make the breaker trip, but I assume whatever it is can't be helpful to connected loads.  

JRHill

Ralph Day said: (but don't tell the insurance company...supplemental to them)

I installed a ventless propane unit specifically for this purpose. The agent who came to take pictures just smiled cause it was obvious that the wood burner was our primary heat. What he was concerned about was the wood burner in my shop. But he took pictures where the chimney was out of view. All he said was to be careful with it.