I live near Boston and have a 4,400 sq ft house (closed-cell spray foam, new windows, energy star appliances, LEDs, etc....) with a Hydron HXT060D Geothermal unit (installed last spring) and a standing column open-loop well. We were very pleased with our electricity bill in the summer and fall, but come winter things started to get expensive. Our December bill was over $1,100 (!!!!) and our January and February bills were only slightly under $1,000. I bought some energy meters and I saw that even when the heat wasn't on, the air handlers (we have 2, one for first floor+basement and one for 2nd floor+attic) each used ~3,500 watts and were running more than half the time 3.5 kilowatts/air handler * 2 air handlers * ~16hrs/day * ~30days/month * $0.22/kwh = ~$740. Voila, we have our culprit! While I'm open to considering options for replacement air handlers (even though these are brand new), I'm wondering if there's simply a way to raise the output temperature from the geothermal unit which would hopefully allow me to move more BTUs into the home with less time from the air handler. Alternatively, is there a way to avoid running the air handlers so continuously? Is this normal?
Air handler blower motors typically range in size from 1/2 HP to 1 HP. 1/2 HP = 373 Watts, 3/4 HP = 560 W, 1 HP = 746 W. This should be marked on the air handler nameplate. If you are measuring 3500 W for each air handler, then there is more involved than just the blower motor. Do you have electric resistance heat strips installed in the air handlers? More than likely you have the first stage of heat strips (3 kW ?) turning on plus ~0.5 kW for the blower motor. So why would the electric resistance heat strips be turning on? They are controlled via the thermostat and relay(s) in the air handler. You may have a thermostat setup issue or possible wiring issue in the air handler. And yes, you can not have the air handlers not run continuously. This again is controlled via the thermostat. What make and model thermostat(s) do you have?
arkie6, Thanks for your reply! We have Honeywell 9000 series thermostats and, as far as I know, they show "auxiliary mode on" when the heat strips are on. I can confirm that they are NOT on when the air handler is using 3500 watts. In the simplest case, turning the heat off and the fan on alone uses that power.
I'm a bit confused - the HXT is a package water-air unit is it not? So then, why do you also have air handlers?
I assume he refers to the Water-Air units as air handlers. He might has 2 of them for 10 tons total? If a 5 ton unit draws about 3500 when running in first stage, I would consider that close to normal, if pumping power is included.
We have 2 systems for 11 tons total. Air Handlers push the air through the vents for ventilation and to send the hot/cold air from the geothermal pump to the rooms of the house
Still not clear. The Hydron HXT060 is a 5 ton water-air heatpump, which includes a packaged air handler. The vast majority of energy is used by the heatpump, not the air handler on top. Please confirm that your other unit is a HXT072...
060 = the nominal output in thousand BTU. 12,000 BTU = 1 ton. 60,000 BTU output = 5 tons. If you have two of these, you have 10 tons nominal of heating/cooling. You said previously that you had 11 tons total. This would mean you have an 060 (5 tons) plus an 072 (72,000 BTU or 6 tons). According to Hydron Module literature, the HXT is a vertical forced air package unit which means the geothermal heat pump including compressor, heat exchangers, and fan blower are all installed in the same cabinet. The "air handler" you are talking about is the complete geothermal heat pump except for the water loop or supply pump(s). 3500 watts for the power consumed by the entire heat pump including compressor, fan blower, and loop pump(s) is in the ballpark of the expected load. The bigger issue in my mind is why do you have 10 or 11 tons of heating/cooling capacity for a modern insulated 4400 sq ft home? You should be able to heat & cool that home using less than half that tonnage unless you were extremely short changed on the amount of insulation installed. Was a Manual J heat load calculation done for your home prior to installation of the geothermal units?
I may be mistaken. We may "only" have 10 tons. I am out of my league here in terms of what's the right amount of tonnage, but iirc 'yes' a manualj model was put together. As I wrote above, we have closed cell spray foam for something like r25 in the walls and r40 in the roof
The HST060 is a 5 ton split geothermal heat pump unit with separate air handler. The MPD060 is a 5 ton air handler with a 1 HP (746 Watt) blower. The HST060 and MPD060 work together to produce 5 tons nominal heating/cooling. So, do you have a single HST060 and a single MPD060? Or do you have two (2) HST060 and two (2) MPD060?
I have one (1) HXT060D (for the basement and first floor) and one (1) HST060 + one (1) MPD060 (for the second floor and attic). I think they set it up this way so that the HXT and HST could both be in the basement (quieter, less upstairs footprint) and the MPD would be in the attic (closer to the bedrooms)
I can't speak about the packaged unit, but when I was troubleshooting my split, I pulled power from the compressor and was still able to operate the air handler via the thermostat. Maybe try this isolated test if possible and see what the power draw is? Just a homeowner here...
Ok. Where exactly did you measure 3500 watts? Which unit? At the unit or at the breaker panel? Do you have four (4) 2-pole breakers supplying your units? I'm assuming you have (1) 2-pole breaker for HXT060 heat pump compressor, (1) 2-pole circuit breaker for HXT060 blower and heat strips, (1) 2-pole circuit breaker for HST060 heat pump compressor, and (1) 2-pole circuit breaker for MPD060 blower and heat strips. Where exactly are those energy meters connected? Since you have an open loop with standing column well, what type and HP of water pump do you have supplying the geothermal heat pumps?
Hi - Boy, I'll tell you, something doesn't seem right there. We have a somewhat similar set up - 2 3 ton geo units, both in the basement, one a split that sends water to an attic air handler for the second and third floor heat. (And a standing column well). Our house is in NH - maybe a little bit smaller, but our bill is less than half of yours, and, except for the coldest of days, the downstairs unit heats the entire house just fine, so something basic is wrong. As long as you're sure there is water in your well, 2 things come to mind right away, and they are related. I would be willing to bet that your aux heat, your electric strips, are kicking in, and it's because of your thermostat settings. (Someone upthread mentioned this and I fully concur with them) Thermostats for these geo units are all different, and, from what I can tell, even the installers often mess up settings (because it happened to us, and a couple of other folks I know). It took me a year to finally get ours set so that the 2nd stage kicked in when I wanted it to, and, only after I finally installed a different thermostat. Triple check how and when your staging kicks in, and, when the aux heat does. Different thermostats call these things different things, and, often the instructions are counter intuitive. The other basic question is this: you are just keeping the house at a constant temp, right? Any kind of temp set back and yo-yoing temps will give your heat pump fits. Good luck.
