the Walnut Diary

Lifetime DIY fan decides to attach heat pump to oil furnace in 1837 stone farm house.

I first got the idea to do this when the government announced a three-year-window on the carbon surtax on heating fuel for rural Canadian home owners, on the assumption that within that interval owners would install heat pumps and reduce carbon emissions.  After some thought I located a local heating guy and asked him to stop by to see if such an idea were feasible.

I left a voice mail but received no response.  I mentioned this to Les, my retired electrician friend.  He knew the guy and liked him after he had improved the performance of his heat pump.  Les offered to get after Joe and arrange for him to call me.  At length the call came through and Joe arrived in a minivan to look at the prospective job site. 

I didn’t expect much, not after a trusted gas fitter from an earlier house discovered that he had to drill five feet through the stone wall in order to run the line for the new “commercial” range.  I had deliberately steered him away from what I thought was the thick part of the wall, the additional three-foot ledge to support the kitchen hearth. 

When I replaced the doors and windows in the house, though, I narrowed the wide Georgian door in the basement to a more standard size, leaving room in the casing for a sturdy wooden cavity from floor to header, faced with a 1” pine board on the outside and a 2” plank on the inside, with loose fibreglass insulation between.  It had worked well for vents for the central vacuum, the main floor bathroom vent, and miscellaneous data cables over the years.  Joe looked at the panel and decided that it would work fine for the hoses and 220 volt feed.  The control box would screw right onto a bare spot in the middle of the panel.

From that point, Joe made a lot of sense.  The 1” flexible copper pipe is pretty versatile, and we planned how it could snake around the various obstructions attached to the heavy timbers in the basement until it got to the furnace.  The return pipe is made of easily-worked 3/8 copper pipe.

I asked for a quote.  It was reasonable, so I sent him a deposit and waited.  Les had a look in my basement and found a pair of heavy stove cables running along the timbers which were no longer in use.  He suggested I combine the lengths and move the existing dryer cable to an unused 40 amp breaker in the panel (They changed the specifications), vacating a 30 amp for the heat pump.  The shut-off switch I bought at Rona struck me as dangerously shoddy in construction, but Les assured me that that’s how they all are, and it would be fine.

I picked up a trailer load of gravel at the quarry and positioned a quarter of it under the rear deck of the house for a base for the outdoor unit.  One of my favourite toys is a 17 hp Bolens diesel 4wd tractor with remote hydraulic feed.  Years ago I bought it a matching dump trailer with folding sides.  The whole unit will back through a 48” door with a load of firewood, so I decided to put a quarter-yard of gravel on it and back it up the slope to the nine-foot deck and a good point to dump the load so that all rake work would be downhill.  

But first I had to get the gravel out of my 4X8 utility trailer.  I removed my truck from the area, leaving the loaded trailer sitting on its fold-down wheel.  Those safety chains must be strong, eh?  I clipped the large carabiners at the end of each chain to the hook on the loader of my TAFE tractor, removed the trailer’s tailgate, and lifted.  It worked fine, leaving a pile of gravel on the driveway.  Then it was a simple matter to load up the little trailer for the reverse trip up the slope to the job site.  There was just enough room under the deck to dump the gravel.  Hydraulics are great!

Joe arrived the day after Labour Day.  He opened the van door.  The outdoor unit’s box looked huge.  I asked how much it weighed.  “I don’t know.  I loaded it by myself o.k.”  I mentally ran through my toys for handling heavy objects until Joe dropped a heavy hand cart onto the driveway.  He and a silent assistant headed down the hill beside the garage, manhandling that cart, and moved it into position below the house.  Then came the stand.  I was pleased to see that it’s sturdily made of powder coated square tube, and can be adjusted during assembly. 

The intended site seemed ok for grade, but Joe asked if I had a concrete slab, so off I went with the loader to free one from a mat of weeds.  This was the hardest work of the project for me, but I eventually drove the tractor up to the site with two slabs in the bucket.  One plopped down on my stone-ringed pad and required very little levelling.

From there on I decided that it was up to me to stay out of the way and not mess up Joe’s job.

This was not particularly easy for me.  Les pulled rank (as a former tradesman) and got the coveted pipe-unwinding job.  He actually got to stand on the pipe at one point.  I managed to hold the big copper coil when Les had to help bend pipe, but that was the most responsibility I managed to earn.

It turned out the indoor unit needed the space over the burner in the oil furnace currently occupied by my much-calcified humidifier.  Out it came. That triangular tube-thing was rather fascinating.  I took a lot of pictures of it before it disappeared behind a sheet of thin steel on the side of the furnace.  Joe precisely marked and cut holes for wires, two tubes, and a drain.

Things went very well until it came time to pump all air from the welded pipe and in-furnace unit.  It wouldn’t maintain a vacuum.  Joe suspected his pump after he had easily found and corrected a leak In one weld.  (I call it a weld because he uses a small oxy-acetylene torch and silver solder.  I wondered why there was no flux.  He said it’s in the wire.)

The following morning Joe was back with another pump and the system vacuumed out easily.  Then Joe released the coolant and oil which are stored in the outside unit.  Then he installed the thermostat.  Earlier I had run the eight-wire cable down to the furnace by attaching it to the old thermostat wire.

The unit works as promised.  It cools and it heats.  Joe, Les, and my wife made it clear that I was not to use any of my burnt-fingers experimental techniques on this device, especially the Internet accessible thermostat controls.  Les further forbade me from hooking the 220 circuit into the generator panel, because “Your generator’s power isn’t refined enough for this expensive unit.  In a power outage, just run the furnace.” 

O.K.  I had recently burned out a new angle grinder by not bothering to adjust the hertz level of the power for a quick job cutting off some rebar a long way from my meter.