Hello,

I thought it was nice to see how others set up their shop and maybe we all could learn a good idea or two from it. So I thought I'd review my installation of a heat pump (mostly will be used for air con) and how well it works.

In the southwest here, it can get pretty unbearable in the summer. My better half suggested I put in air con to make working in the shop not such a miserable experience.

Being it's a regular outdoor metal building, it was never intended for an HVAC system so there is no air handler, which made the decision to use a European style mini-split system as it includes the interior air handler. The cheapest 2 ton unit (1 ton = 12,000 BTUs) I could find was this:

This is meant for a finished interior wall, so I had to make some brackets to accommodate the interior unit.

The outdoor unit I elected to hold off the ground and the required distance away from the exterior wall. So I made a heavy duty bracket that will hold it up and off the wall.

After finish welding and painting and installation.

Although I still need to move the gutter....

This is the interior brace on the other side of the wall to spread the load/weight of the outside unit and bracket.

Because it is a heat pump, and can heat instead of cool, the outside unit has a condensate drain on it as well. So if mounting on the ground, you need enough room for the water to run out.

As far as tools you'll need besides the usual construction tools are these HVAC tools.

The middle brass adapter is a R410a to R12/R22/R502 adapter and of course you'll need a gauge set (checking vacuum only), so any R12/R22/R502 gauge set will do and a vacuum pump. The outside unit comes precharged with the exact amount of refrigerant and oil for the included line set and interior unit, but after you connect the lines you need to draw those components down to a vacuum and check for leaks before opening the Rotolok valves on the outside unit.

As a side note as the unit is precharged, you best not alter the line set length in anyway, otherwise you'll have to calculate the new required charge with R410a rated equipment. In my opinion, it's a hassle and not worth it, just find a place to route the extra line if needed.

I ran my extra line up across, down and over.

The only part left after the refrigerant lines are run, connected, evacuated and charged is the interior unit condensate line and the electrical.

After that, test it, button it up and enjoy it.

My shop is 1200 sq feet with an ~13ft pitched ceiling. This little thing keeps that place 80˚F or cooler when outside temps are mid to high 90's.

A couple of things worth mentioning. This unit uses all 3 phase motors (both fan motors and compressor) it has onboard VFD's (variable frequency drives) that convert the incoming single phase (or phase to phase) 220 VAC to DC then recreate the 3 phase power from that. As a result, they were able to incorporate a really slow start sequence on the fan motors and compressor and the inrush current is practically naught. 3 Phase motors are much more efficient at converting electrical energy into mechanical work and as a result draws much less current at full load (~ 9 amps @ 220VAC) than our house central air con (R22 unit 2-1/2 ton, single phase compressor).

Another really neat feature this has, is the colder you set it, the faster it spins the compressor and as a result with a large differential in set point temp and room temperature, it will jet out meat locker freezing cold air. Actually with a Tee shirt on, it's too bloody cold to stand in front off. Set the temp closer to actual room temp and it slows down the compressor and it will jet out cool air.

In summary, for the money, it's a great buy, now how long with the cheap, non brand "Air Con" hold up? Who knows, but for the past few weeks, it's been working great. And I should mention, it's so whisper quiet you could use this in a library. And installation on a finished wall may be actually easier than having to make brackets for the inside.

ADDITIONAL NOTES :

A little more about 3 phase motors and starting current. The reason the starting (inrush) current is so low on this particular heat pump unit is because of its VFD design. If you were to take those 3 phase motors and directly switch them to a 230VAC (60 Hz) standard 3 phase line, they would have a considerable in rush current from a standstill position similar to any other single phase motor. The reason for that is you can think of the induction motor as a simple transformer; the fixed windings are the primary and the rotor is the secondary. When the rotor is at a standstill, it can not offer back back emf and therefore acts like a short. Hence the high starting current.

When I was waiting for the paint to dry on the bracket for the outside unit I became a little bored and with my insatiable curiosity of how things work, especially electronically. (Used to be an electrical engineer by trade) I tore apart the outside unit. Imagine my surprise when I found a massive control module with quite a bit of intelligence. This VFD also has sizeable (externally mounted) switchable reactors (transformer with just a primary winding) to help wave shape and control the voltage to the newly created 3 phase power from DC.

As a result when it starts the fan and compressor motor, it starts them off at 0 Hz at low voltage and slowly steps them through the phases gradually increasing the speed and the peak voltage. Once a certain angular velocity is reached it switches in full voltage, hence the really low starting current.

Concerning vibration/noise from mounting the outside unit directly to the wall. The only time it's noticeable is when it starts slowly spinning up. The compressor on the slow start ramping speeds hits a resonant vibration and you can hear that, but it only lasts for a couple of seconds. When I installed our house central air con. I put the outside condensing unit on those extra body mounts included in the 3rd gen galaxie body mount kit and fastened the whole thing down to large concrete paver blocks so there's no danger of line flex/breakage.

The next body mount kit I buy, I'm going to use the extras for mounts for this outside unit on the bracket. Actually I use those extra body mounts for quite a few things, such as the propane furnace in the shop (suspended from ceiling) and the 2 hp exhaust blower for the make shift paint booth.

The reason why elected to suspend this outside unit off the ground, is one, when monsoon season comes, that whole area puddles up pretty badly, and also sometimes we get hit with a good snow fall and the wind piles it up right there.

I know working out of a car port can be really hot in the summers. We have an enclosed all metal car port (30' x 31') and it's an oven in the summer. Building a garage and insulating it will be a nice change for you. What size is your footprint you have to work with?

As a side note, yesterday there was a power cut that last lasted a few hours, so as an experiment I dug out the crappy old 5000 watt 10 hp generator. You know the ones that are so cheap they are insanely loud (2 pole alternator needs 3600 RPM's for 60 Hz).

Anyway, I could never start our house central air con unit on this generator, the inrush current is too great it just pops the breakers on the generator and the engine sounds like it's having a coronary.

So I turned this "Air Con" unit on and the generator didn't let out the slightest change in RPM. A minute later and I had cold air.

Cheers.

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