Quote:
Originally Posted by timun
In Calgary's climate the requisite heating capacity is significantly more than cooling, so it's not uncommon that either 1) the cooling capacity is grossly oversized and you get short-cycling as you described, or
2) you quite deliberately undersize the heating capacity and leave the deficit for a "back-up" gas-fired or electric (resistive) furnace. Option 2) isn't so bad really, as you need the additional heat source for peak conditions anyway, but it means deliberately less use of the heating cycle and not taking advantage of outdoor conditions where the heat pump's COP could be significantly better than the thermal efficiency of your furnace. |
Quote:
Originally Posted by Street Pharmacist
This is a interesting wrinkle I wasn't aware of. I wonder if there could be a way fix this from a technological standpoint? Like maybe reduce the cooling intensity to avoid the short cycling?
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It's really not an issue at all. Almost everywhere with any kind of real heating/cooling needs has a mismatch between heating and cooling loads. You just size the equipment for whichever is more appropriate; generally that's heating for heating-dominated climates and cooling for cooling-dominated climates.
Short cycling can be an issue, but it's more of a problem with modulating equipment. My main heat pump can output between 3K-26K BTUs in heating or cooling mode, so if the cooling needs are less than 3K, then it'll kick on and off pretty regularly which isn't great for units that are designed to run 24 hours a day. But by the time it gets warm enough inside to warrant turning it on, the cooling needs are at least that high.
And with non-modulating central heat pumps, they're not designed to run all the time (except at the design temperature) so they can easily handle turning on and off a few times per hour which is basically what happens during smaller indoor/outdoor temperature deltas. And if it turns into a real issue, it's trivial to get a thermostat that can have minimum cycle on/off times set on it.