We currently have a Climatemaster Tranquility series geo unit. Installed 2013. So far expansion valve failed in second year of operation. Control board failed after 3.5 years. New one overnighted at our expense was bad (according to our repair person who spent most of the day on the phone with tech support). Waiting for another control board while running emergency heat with outside temps at zero degrees. We are considering fairly soon biting the bullet and installing a new unit going with Waterfurnace as that is the brand recommended by our current HVAC company. BTW, original installer had no clue how to repair geo units so we found and switched to current company. Very limited where we live, but remote. Company pushing 12 stage over 2 stage touting big usage saving. We have open loop from 85' well, variable speed pump. Can anyone tell me if the 12 stage will truly be a significant electric usage savings. Also with 12 stage will there be more parts to fail. Appreciate any help we can get with this decision of 12 stage vs. 2 stage. House-one level, 1500 square feet, 8" logs, triple pane windows. We have separate switch to never allow emergency heat (except now with broken unit). Keep house temp between 55 and 62. Thank you to anyone who can offer advice
For the "12 stage" (Series 7) to deliver promised savings will require careful attention to the water side. Because the S7 can ramp so far down in capacity it tends to run many more hours than a conventional single or two stage system. It is not unheard of for an S7 to operate 50 - 100% more hours annually than a lesser system though at much higher efficiency. That said, the efficiency gain can be overwhelmed / lost completely if during all that extra run time an inefficient pumping solution is deployed. In a lower cost electricity market the savings of the S7 vs S5 may not recoup the increased first cost.
In our climate zone, similar to yours, we runtime for the 7 series between 6000-6500 hours annually, compared to 2500-3000 hours for a dual stage. Open systems use significantly more pumping power, they have to overcome the static pressure in addition to the pressure from from the pipe. For that reason I would always consider a dual stage over a variable speed in an open setting. That being said, I am a big fan of the 7 series, we see real operational benefits of 15-20% plus significantly higher comfort (no noise, no draft), but you need a really evolved installer and a close loop setting to get the efficiency benefits out of it....
