Hello,

we had a geothermal heat pump installed during the summer, and we are now starting to use it for heating.  To me it seems that it runs very often and for a long time.  It is not cold here yet (just about 0C outdoors), so I am wondering how it will keep up when winter starts.  Right now it is coming on about every 15 minutes, and running for about 5 minutes at a time.  The setpoint is at 20C.

The unit is a Waterfurnace Legend 5 ton, horizonatal configuration.  It looks like it is working right, the air Delta-T is 25.5F.  I haven't checked the water side yet. 

Are these cycle times normal?

Thanks,
Ord

It is hard for us to verify cycle times, but I can tell you two things.
1) systems in my area may run in first stage more than 60% of the hour at 0*C. with multistage equipment systems can run 100% of the hour at just a few less degrees though in first stage not second or third. Much of this has to do with installer's design philosopy and geographic location. Your use of C vs F suggests you are North of me and therefore likely subject to colder winter weather, so while your description of your heat pumps behavior might suggest it was oversized in my area it may be just right in yours.
2) If your installer gave you a comprehensive op cost calculation with bin report, it will show you exactly how much of the hour system should run at a given temp.
Good Luck,
Joe

Sounds about right. I assume you are in Canada, given your metric settings, Which also means that you are likely heating dominated. The Legend series is a single stage heatpump, so what your are describing is that the heatpump is running at about 1/3 capacity, which seems to be OK giving 0 degrees outside. You can likely adjust your thermostat to run longer cycles if you wish. 2-3 cycles per hour in the shoulder season sounds reasonable. The lesser the better, but I have not found a good definition of "shortcycling".

Thanks Joe.

I am located in Eastern Ontario, Canada. In January we can expect the average temperature to be about -10C, with average lows of about -15.

I did not get a detailed report from the installer, so have no idea how much of the time they intended it to run. The only real details they gave was that it was intended to provide about 90% of the heating on the heat pump, and the auxiliary heater would provide the last 10% on the coldest days.

Thanks also Docjenser.

The only thing I could find in the owner and installation manuals about cycle times was a note that there was a short cycle protection which keep the compressor on for a minimum of 2 minutes, and off for 5. Now that you point it out, running at about 1/3 of it's capacity does make sense for this time of year.

Might want to bump the Cycles Per Hour (CPH) down to 2 or so if the thermostat has that feature. Then it might run for 10 minutes every 30 and be more efficient. That would be easier on the unit as well. The downside is that house temperature swings more widely with decreased CPH