Geothermal, Aux Heat, and Desuperheater

So this AM after my normal morning shower, dressing routine, I almost always go and check the thermostat before going downstairs.  I do this because the programmable T-stat lowers the temp automatically at 7am when we're typically done the getting ready routine.  If I'm early, then I like to manually lower the temp to save some energy.  I had also noticed recently that Stage 2 was running a lot...but I had chalked that up to the cold temperatures outside.

Well, today when I checked the t-stat, I saw the aux heat was on.  REALLY?!?  WTF?!?  (Note:  The Aux heat is 5 kW in each unit).  Yes...it was cold this AM (20F), but there should be no reason the Geothermal can't handle it.  It's not like the system is seeing the 20F.  So I quickly lowered the temp to turn off the aux heat and ran downstairs...to find the same thing.  The f*#$ aux heat was on!  So that's 10 kW of extra electrical demand.  Checking my TED 5000 confirmed the aux heat was on for roughly 40 minutes.  That's an extra 6.7 kWh added to my bill.  And yes...it appears it was on yesterday too.

Extremely pissed off, I went online to see if the thermostat was setup incorrect.  I'll tell you what...the instructions on thermostats when it comes to these settings is damn near non-existent.  I gave up and went to the T-stat settings (each one) and turned the Back-Heat to "Economy Mode", and turned the "Heat Control Mode" to "Less Aggressive".  While there, I did the same for the "Cooling Control Mode".  This was kind of arbitrary at the time. 

I did some further searching later in the AM.  I ended up in the GeoExchange forum finding that most thermostats aren't made for geothermal systems.  So their default settings are NOT appropriate.  Looking at my settings, the Stage 1 is set to run at 3 cycles per hour (CPH), Stage 2 is 3 CPH, and the Aux heat is 9 CPH.  From reading the forums, most people have set the Stage 1/2 to either 1 or 2 CPH which apparently increases efficiency (i.e. allows each Stage to run longer).  It's slightly confusing because the lower the number, the better apparently.  The definition is:

"cycle rate is the ideal number of times a heating system will run, in an hour, to maintain temperature within one degree. For instance, gas or oil forced air systems have a recommended cycle rate of 6. With a cycle rate of 6, the heating system, at a 50% load, will cycle 6 times per hour. This breaks down to about 5 minutes on and 5 minutes off. Again, the actual on and off time of the heating system will vary as the load on the heating system varies."
So a setting of 3 is 10 minutes on/10 minutes off.  And if this is correct, then a setting of 2 is 15 minutes on/off and finally a setting of 1 is 30 minutes on/off.  Going with a longer run time allows for more air movement and a more "steady-state" operation. 

I found a good explanation of CPH below:

"CPH, is the digital equivalent to the old heat anticipators that actually heated the thermostat.

In Honeywell thermostats its just an algorithm based on previous on and off times, to attempt to maintain an X amount of temp differential/deadband/droop, by increasing or decreasing the on and off times. And is only accurate when the homes heat loss or gain is at 50% of the equipments heating/cooling capacity. The size of the equipment will determine when the thermostat can maintain its set CPH. And as the outdoor temp varies, the actual CPH will also vary, and the duration of the on and the off time will change accordingly with one increasing and the other decreasing.

A thermostat set for 3 CPH, will have a continuous run time when the outdoor temps and indoor set temp are at design conditions, and the heating or cooling equipment is sized for those design conditions. If the outdoor temp rises 5 degrees above outdoor design in winter, even with the CPH set to 6, the system will be cycling at 1.5 or 2 cycles per hour. If it rises another 5 degrees, the stat may begin to have 1 or 2 minute off times, which becomes very annoying and hard on the equipment.

Temp over rides CPH setting. The thermostat continually monitors temp, And recalculates when it should bring on the heat or A/C. And how long it should run it. And then when it brings on the equipment, in monitors the progress and recalculates how long it should keep on running the equipment. Along with how long it should keep it off once it shuts the equipment off. It is constantly recalculating the on and off time by monitoring the temp. Temp over rides CPH setting.

A higher CPH means more on and off times an hour, so the equipment will short cycle. But maintain a very tight temp control of the hose. Very comfortable, but hard on the equipment.

A lower setting will allow a wider temp swing in the house, and be much easier on the equipment. The temp swing increase will only be a few tenths of a degree."

I've seen stuff back and forth on setting the Aux Heat to the same as the heating/cooling...so maybe I'll do that as well.   I also found out that with my outdoor temperature sensor, I need to turn on the "Outdoor Temperature Aux Heat Lock Out" which locks out the use of the Aux heat if the temperature is above a specified temperatures setpoint.  I've seen numbers flying around but I would think it would make sense for this to be 30F just in case the Geosystem goes down and its below freezing to prevent any water pipes from freezing/breaking.  Finally, there's a recommendation to change the delta between Stages 1 and 2 to be 3F so the first stage will run more often.  However, my thermostat doesn't have this feature oddly enough....the closest I have is "deadband".  There is an upstage timer which I think I could use...but I'd need to check.  Increasing the timer means that Stage 1 will run for XXX minutes and then if the timer expires and the temperature has not yet been reached, then Stage 2 will come on, etc.  I'll have to play with this that's for sure.

Oh yeah...almost forgot about the desuperheater.  In the same forum I came across some folks talking about the desuperheater.  Apparently I need to check out my installation.  I've talked about it previously, but the most efficienct system uses a pre-heat tank and then the hot water heater (HWH).  I don't have this (yet) so I only have my HWH.  Well...apparently I need to make sure my upper and lower elements are at different temperatures. So the lower one needs to be set at 100F while the upper is at the normal HW temp...say 120-130F.  This is because the desuperheater measures the water temperatures.  If its above a setpoint (130F apparently), then it doesn't turn on (it says the HWH is already at temperature...don't bother).  Well...I think my lower one is set to 120F and I've never checked my upper one.  I know the installers didn't change anything because my HWH has a insulation blanket around it...and to get at the element thermostats you'd need to either remove the blanket or cut a hole.  Neither was done beacuse I cut a hole in the blanket to get at the lower element this fall.  So I definately need to change these settings!  And I was wondering why I didn't feel like I was getting any "free" hot water from the desuperheater...that's because the HWH was maintaining the 120-130F setting and the geothermal system would sense it and say not to use the desuperheater or it would run minimally.  Dang it!!!!!!  Well...that'll be fixed today.  Also, I need to insulate the piping from the HWH to the desuperheater.  Looking at pics it doesn't have any insulation on it and I need this to (a) get a good temperature reading and (b) to make sure the heat that it put in is actually making it to the HWH.