Heat pump running continuously

I have a good man 2.5 ton heat pump system this will be my second winter with it. Some background info, it does not have any aux heat coils, and I only use this to heat during spring and fall when temperatures are mild. I've never had a heat pump before nor have I ever lived in a house with one so this is completely new to me. I'm used to a traditional system running until temps are met then shutting down. Last year it seemed like my heat pump ran all the time at night, even when temperatures seemed mild. This year I seem to be having the same results. The other night it fell into the mid 30s, and I had the thermostat set at 72 all night. I'm pretty positive it ran all night long, and when I woke up the temp was 71 on the thermostat. Last night was much more mild, with lows in the 40s. I had it set back to 67 for the night, I know at 10pm it was not running. However I woke up some time in the middle of the night and it was running, as well as when I woke up at 5 this morning.

I know its pretty common for them to have long runs times, but from my understanding I don't feel like it should be running continuously through the night when it's fairly mild out. During the day I don't think it runs much, if at all. When I get home from work it usually is not running. During the summer, even on hot days in cool mode, it doesn't run all that often, and when it does the run times aren't all that long.

Does this seem normal?

 

One of the more common causes I see causing this is a bad thermostat though it is possible for a relay in the heat pump to stick in the on position. Turn off power to the heat pump by flipping the breaker. Remove the thermostat and make sure no wires are touching each other and turn the power back on to the unit. Does it turn back on and run continuously?

 

I actually just replaced the thermostat with a brand new honeywell. I don't think the problem is the relay, the unit does shut off, but the run times just seem very long. I can't say for a fact the unit runs all night, but I can only assume it does. A lot of time it reaches set temperature, but keeps running for a while, then does shut off, i've seen that happen during the day.

Like I said, I know heat pumps are mainly designed to maintain temperatures, but it just seems like it runs excessively for it being mild out. This morning once temperatures reached the desired temperature it did shut off, and hasn't come back on since (its very mild out today.)

 

That's the way a heat pump works...... slow and steady.

When the heat pump was installed was it designed as a primary heat source ?
In other words..... was it designed to completely heat the house ?

Running the heat pump in heat mode with a furnace available is only beneficial if the cost of the electricity to heat is less expensive then the cost of gas.

 

The heat pump was installed strictly as a supplement heat source, I don't have any electric coils installed in it, so it strictly runs off the heat pump only. My main heat source is an oil fired boiler, which oil is very expensive, and I actually don't even use it anymore. I use a coal stove throughout the cold months that's tied into my ductwork as my main source of heat. The heat pump is only used in thr milder months where it would be too warm to run my coal stove, so the load on the heat pump isn't all that expensive.

From my understanding heat pumps are highly efficient and are one of the cheapest forms of heat, is this not true?

​​​​​​Makes me feel better atleast knowing that is how they are supposed to operate.

 

Yes.... your understanding of them is correct.
And just like a central A/C.....if the refrigerant is low.... the efficiency suffers.

 

Should I have the refrigerant level checked? The air coming out of the vents in warm, and the supply line on the line set is hot to the touch when running.

The unit was sized for cooling my house, that was the reason for install, with the intention of using it to heat under mild conditions. I'll use it until temperatures starting dropping below freezing.