After much discussion the time came to properly heat and cool the workshop. I’ve spent the last couple of years researching the options and concluded that the best solution was a mini split heat pump.
Mini splits are known for air conditioning. They also serve as heat pumps, down to ~30 degrees. There are models of mini splits that function as effective heat pumps down to 0 degrees – some even work as low as -15 degrees! These special mini splits are known as hyper heat, which was the name Mitsubishi applied to their pioneering low temperature units a number of years ago.
So we asked for a quote from Northboro Oil. We’ve been doing business with them for over 30 years, always receiving excellent service. We had them install our central AC 12 years ago, and our only complaint there is that we didn’t do it 25 years ago!
Paul came out, checked the workshop, and listened to what we wanted. We received a quote which was, as expected, expensive. My research showed that the vast majority of problems with mini splits were installation related. Our experience with Northboro Oil is that they do good work and don’t cut corners, which is what we wanted.
The quote was for a Fujitsu Halcyon AOUG15LZAH outdoor unit and ASUG15LZAH indoor unit. This is rated to heat down to -15 outdoor temperature, which should be fine since our area very rarely goes below 0 and is usually 10-30 degrees in the winter. Fujitsu is one of the top three makers of mini splits, so the quality and longevity of this unit should be good.
At 15,000 BTU cooling this unit is smaller than I expected – I had been looking at either an 18,000 or a 24,000 BTU unit. Actual heat calculations showed a cooling requirement of 8,000 BTU based on the design and insulation of the workshop. The biggest concern was whether or not the 15,000 BTU unit could ramp down enough for effective de-humidification. Not the outcome I expected!
There were some concerns about heating capacity, as this unit looked marginal. This was based on keeping an indoor temperature of 70 degrees on a 2 degree day. My needs are closer to an indoor temp of 60 on a 10 degree day, which produces an answer of “OK, its fine then.” The old electric heater is still hanging from the ceiling as backup/booster; it might as well stay there until I need 220V service in that corner of the workshop.
I called them on Monday to accept the quote and see about scheduling installation. The date was set for two weeks out. This was a pleasant surprise – I had been hoping for a month and wouldn’t have been surprised at 2-3 months. Things were looking good!
The next morning I got an 8:00am call from Northboro Oil: “A job we had scheduled for today isn’t ready. Can we install your mini split starting at 9:00am today?”
Umm, yes?
The crew showed up at 9:00 am and had most of the work done by 5:00pm. They came back Wednesday morning and had all of the mechanical work finished by noon. This included leak test by pressurizing the system to 400 psi with nitrogen and waiting an hour to see if the pressure dropped. This was followed by a vacuum pump to remove all air and moisture from the lines and then waiting another hour to see if the system held vacuum. Both of these were successful, so the valves on the indoor and outdoor units were opened allowing the Freon to flow through the system. Well, it is actually R410A, not Freon, but you get the idea. The only thing standing in the way of cool air was electrical power!
The electrician came by in the afternoon to scope out the electrical work.
The electricians showed up at 9:00am Thursday and left by 9:45. This included time spent discussing the Imperial and the workshop…
I had done all of the rough wiring for the AC before insulation and sheetrock. This included the 220V AC Disconnect and the required 120V service outlet on the outside back wall of the shop. All the electricians had to do was run a waterproof whip from the AC Disconnect to the mini split, swap out the 30 amp breaker for a 20 amp breaker, and connect the 4 wire control cable between the indoor and outdoor units of the mini split. The electricians were quite happy with me, saying “you did all the hard work for us!”
I thought about doing the electrical myself, but ultimately decided to have them do it. If there are any problems they own the whole thing and there aren’t any questions.
Of course we are now having mild weather, with temperatures in the mid 70’s, making it difficult to really try out the AC. The inside temperature of the workshop is 75 and the Imperial, fresh from a 70 mile run, is parked inside with the 413 radiating heat. The thermostat is turned down to 68 and the temperature is dropping.
Both the indoor and outdoor units are virtually silent – to the point that I can’t tell if they are running unless I walk up to them. I think I’m going to like this setup!
Update:
Day 2 of a heatwave. 95 degrees outside, 71 degrees inside. I can live with this!
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