Thursday, February 15, 2024

The conundrum of heat pumps - my experience

I had a heat pump installed just about a year ago now. Always keen to reduce my carbon footprint - I'm the guy on the block with the electric car, the PV solar panels, and the hot water solar panel - a heat pump seemed like no-brainer. Indeed, I was surprised I had waited so long to do it.

Anyway, after doing my due diligence, including a lot of research on different models, costs and savings, YouTube videos, you name it, I went with a Carrier model installed by Reliance, a large enough company with apparently plenty of heat pump experience. 

The Reliance sales guy seemed pretty clued-in about heat pumps, and he answered most of my remaining questions. I happily agreed to the energy audit before and after installation in order to quality for the $5,000 federal grant towards the S16,000 cost (for a heat pump and a compatible gas back-up furnace). The installation went well (in a snowstorm!), and everything seemed to be going swimmingly.

And not only "seemed", but really was: the heat pump worked well from early March onwards. Our electricity bill went up, but the gas bill went down significantly, all as expected. I switched the heat pump off in spring, as we have always switched off our heating as soon as it's warm enough. 

The Ecobee digital smart thermostat was brilliant, and we could enter in vacation settings, check temperatures in different rooms, etc, etc. Very cool.

In summer, we rarely need air conditioning, living by the lake as we do, but we did use it on a few particularly hot days (or nights, mainly), and the heat pump worked fine. A bit slower to cool than our old gas-powered air conditioner, maybe, but it got there eventually, and we felt suitably virtuous.

So, why am I telling you all this? Well, partly to share the news (no longer news) that heat pumps are a good option, even here in frigid Canada. But partly because, after less than a year, things started going wrong. 

At first it was just a minor problem of excess condensation leaking onto the driveway during the heat pump's regular defrost cycle. Not a big deal, but I got Reliance's service guys in as it was all covered under the warranty anyway. 

Nobody really seemed to be able to fix a small problem like this. Most of the guys that came out knew little or nothing about heat pumps, which didn't help. Some of them tinkered with this and that, and probably made everything worse.

Anyway, after a while - we're in late December now - the whole heat pump iced up, and by early January it stopped working completely. We still had back-up gas heating, so it wasn't a major inconvenience, just an annoyance. 

I was now insisting to Reliance that they send someone who actually understood heat pumps, and eventually they did send a heat pump "specialist". Of course, the first day, he couldn't stay long enough to do anything useful. Then, we were away for a few days. Then, he caught COVID. It was mid-February - today, actually - before he could spend any time on it. He re-wired the control panel (somebody, one of the repair guys I assume, had clearly botched it), and re-set some stuff on the thermostat.

But the final thing - and the point of this interminable blog entry - is that he re-set the threshold temperature setting at which the auxiliary furnace takes over from the heat pump from -12°C (which is where I had set it) to +9°C (which is where he said that the manufacturer, Carrier, recommended it). 

So, that would mean that the heat pump would not be used whenever the outside temperature dipped below +9°C, which, in Toronto, means all of the winter as well as early spring and late fall. In fact, just about the only times I would actually be able to make use of it would be maybe April and October/November! The payback period just went up many-fold.

After all, the unit was supposed to be usable at -20°C, even -30°C. I re-checked the interwebs and, yes, there were a whole load of articles saying that heat pumps did indeed work to -10°F (about -20°C) and below. Lots and lots of articles saying don't believe what the manufacturers recommend, they do indeed work at ultra-low temperatures. There is this thing called the "balance point", where inefficient heat pump performance at low temperatures balances out the extra costs (and carbon enissions) of using auxiliary power, but even that is a very low (if slightly nebulous and elusive) figure.

Anyway, I tried to contact Carrier directly to find out where that +9°C threshold came from. I couldn't get through on the phone, despite trying during regular office hours. The email contact form kept telling me I hadn't completed the Captcha correctly when there wasn't actually a Captcha to complete. I did finally get through on the online chat system, where a young lady assured me that of course I could use it at lower than +9°C, I should just play it by trial and error.

So, now I just don't know. Did I break it by insisting on using at at too low a temperature? Did the Reliance repair guys break it with their tinkering? Who should I believe? Luckily, I am pretty well sold on the technology, otherwise I might well be trading it in right now. But I have to admit that my confidence is a bit shaken. And if I can't be confident about heat pumps, then what chance does a much less-committed environmentalist stand? It's a conundrum.


After the heat pump was finally repaired by someone who seemed to understand what he was doing (re-wiring the control panel, for example, after a previous repair guy had messed it up), I set the Aux Heat Max Outdoor Temp to +2°C and Compressor Min Outdoor Temp to -1.1°C. The heat pump did come on when the outside temp was -1°C. Promising. Over the next few days, it seemed to be working fine - heat pump when the temperature was over -1.1°C and gas furnace when it was below.

From here, I guess I will experiment with reducing the threshold degree by degree, while keeping an eye on the frost buildup on the heat pump compressor, and whether it seems to be having problems attaining the target heat. So far, so good. It shouldn't have to be this hard, but it is what it is, as they say.

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