Heat Pumps in Teen Temperatures
maine_tyler
| Posted in General Questions on
-19 F tonight, whos runnin their heat pumps?
-34 F dewpoint. -44 F windchill.
Heat pumps running ok?
Bonus question, does having oversized systems help when it gets this cold, or is the capacity drop of any sized unit past -13F make it more of a moot point? (pretend it were to stay below -13 for a prolonged period of time).
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Great questions and I pray many responses will appear. We are at the nh-ma-vt intersection. We were doing just fine with woodstove and a few space heaters till yesterday, at which point we finally fired oil furnace (first time this season). We plan to run oil furnace till tomorrow, when temps should reach a balmy 40°F outdoors.A mechanical engineer is in process of speccing ashps for us. I’m so glad we have not gotten rid of our oil furnace yet, because the Mitsubishi hyper heat units I believe only work till 13° below zero F; last night it was 18 below zero for several hours. What would we have done had we scrapped the furnace and installed the splits?! We are Planning a future chainsaw retrofit which I’m sure Will bring us to a much lower blower door result than where we are now. Nevertheless, still im skeptical that ashps are safe on design days such as today, yesterday and esp last nite
Our two minisplits (Fujitsu) kept putting out heat. Low temperature was -17°. Inside stayed comfortable at 69°. Our design temperature is zero°.
Hi, Stephen. If you dont mind being asked, what are your: a) sq footage and b) blower door numbers? Just trying to get an idea of how tight a house needs to be for ashps to work even in extreme design nights and days. Thanks
My Mitsubishi MXZ-SM36NAMHZ-U1 kept up with the cold last week, -15
In December just before Christmas we had a very cold night and saw -19°F for an hour or so just around dawn. Our Mitsubishi H2i 48K unit kept going to our surprise and we stayed around 70°F but with frequent defrost cycles. The unit may appear oversize, but we live at 8100 ft so derating for altitude takes it down to around 42K, and the output at -19°F was much lower yet - but thankfully enough.
Still having issues with one of my mini splits (mxz-3c30 hyper heat). Temps down to -13 for a few hours but it stopped keeping up yesterday in single digits around 4pm. Not sure the issue here but downstairs was 38 this morning according to thermostat. Heat pump was running full blast but blasting cool air.
Upstairs is a different story, different unit 3c24 hyper heat kept the rooms warm all night.
Difficulty with getting my installer to acknowledge a problem but I think I’ve narrowed it down to the one unit. We’ve also had crazy high electric since installing this system and I thought that was normal- looking like it’s part of the issue.
Hope others are staying warm!
If you hit 38 degrees in one night you must have serious infiltration issue.
Agree, sounds like you have 2 issues. An equipment issue, and a building envelope issue. No matter your heat source you shouldn't lose that much heat overnight in a decently constructed building it should take days to drop to 38F.
Well I’m still trying to narrow it down but the heat pumps upstairs were fine while the downstairs units just stopped blowing warm air. Felt like maybe 50-60deg air at best.
It’s possible there’s a building envelope issue but I also think there’s an equipment issue here. I’ve done extensive air sealing and insulation in the past year so I don’t really know where to begin.
Tech is coming out to check charge in units, crossing my fingers that’s the issue.
Blowing cold air for awhile is what I had also. The defrost cycle is only 10 mins. They replace the reversing valve on my system. However, my electrical usage is out of control, over 800 kw a month.
800 kWh a month isn't necessarily that much. In fact it's pretty close to the average usage in many states.
Try 3000kwh per month for my system! No clue what’s going on here
It is probably working as expected... best way to find out- measure the temp rise over the coil that is - discharge minus intake air temp - if over 30-35f - your minisplit is not your problem.
For those of you with these hyperheat units in the really cold cold we've been seeing these past few days, when you say the units are still "putting out heat", are they putting out ENOUGH heat to maintain the intdoor setpoint temperature?
What will eventually happen at some point is that the unit will no longer be able to maintain the indoor setpoint, and at that point the indoor temperature will start to track the outdoor temperature as the outdoor temperature continues to drop. Once that occurs, and you're no longer maintaining the setpoint, I like to say you are "losing the battle". At this point, you can only maintain a delta between indoor and outdoor, but you don't have enough capacity to raise the indoor temperature any. At some point with a heat pump, you end up where you can't even maintain that delta anymore, and then you have essentially no heat from the heat pump.
In the first situation, when you start "losing the battle", a larger heat pump (or more of them) would be able to provide more BTUs and maintain the setpoint larger. This would be a "system sizing" issue, where more system capacity would help. In the second situation, a heat pump is no longer able to heat at all, in which case you would need an alternative source of heat, some kind of "auxillary heat" system. I'm curious where people are seeing each of those two situations begin in terms of outdoor temperature.
It is true that heat pumps have a low limit on exterior temperatures below which they can't function, but I've seen some detractors claim much higher temperatures where that starts happening than is usually actually seen. The more interesting temperatures to know are when you start "losing the battle", since if that happens enough with "properly sized" systems, then we can say it would make sense to install slightly larger systems to be able to handle those extra cold nights.
Bill
Bill: We avoid losing the battle by having a tight, well insulated house. If we had no heat at all last night, it would certainly have dropped the indoor temperature, but not to anything intolerable. Every house loses heat eventually. The trick is to minimize the heat loss until the outdoor temperature reaches close to the 99% design temperature, at which point the heat pumps should keep up.
Our system is probably a bit oversized.
Of course, it's much easier to accomplish this with new construction. Our previous house was a big, leaky 200 year old farmhouse with no heat upstairs, but a greatly oversized oil furnace that kept us warm enough, but at great expense.
A tight, well insulated house will still have some point where you begin to "lose the battle", but it might be colder. All a tight, well insulated house changes is that you need fewer input BTUs to maintain the setpoint temperature inside -- you'd be able to get by with a smaller system overall. Everything else would track a home with less insulation or air sealing, although such a home would probably have a steeper slope if graphed, and would get to the "bad part" more quickly.
Bill
Bill.
It's not just that you need less heat input. You also won't start to get too uncomfortable because the house stays warm enough for the extreme weather to be over.
This episode is unusual in that it was both very cold and very windy. In the 30 years we've been in the area, we've never experienced that combination. But it only lasted two days.
Yeah this is what um wondering Bill.
I have a feeling most, if not all, installers in a place like Maine lean towards oversizing (a lot if not a little). Partly out of fear of these types of lows.
But I'm curious what the oversizing really buys you. There is the scenario where the HP output drops below the load demand, but then there is also the scenario where the HP pretty much stops functioning entirely. The latter is not supposed to happen that often, but there are stories... makes one wonder if install issues are to blame.
In the case where the HPs simply can't quite keep up, there is good argument to oversizing in a climate like Maine if one wishes to go solely heat pumps. In the case where the pumps stop working, there is no alternative to having backup heat. And that's the real rub when making decisions about going full bore with heat pumps in this sort of climate: what scenario should we be anticipating?
I know lots of people with old a** boilers/furnaces want to see them decommissioned. Especially if they are already on the fritz; it seems crazy to buy a whole new oil system these days. So what are we to do? Resistance backup? Or trust some over sized pumps? And how much oversizing would be ideal. And does the absolute capacity of a single unit matter more, or the total combined capacity of all units in regards to getting through such a cold snap (like would a larger single, perhaps ducted, unit fare better than many smaller units?) Not simple answers I realize.
Electric resistance backup, if employed on a large scale (such as lots of people switching away from gas/oil to heat pumps), would stress the power grid even more, so there are other problems with that as a backup heat source. I would typically recommend to keep the old system if it's still safe to operate, and only run it when necassary after installing heat pumps to be the primary means of heating over most of the season. You don't *have to* decommish the old heating system after all.
What I'm interested in is how much extra margin in terms of cold weather performance does oversizing buy a typical home before you hit the "too cold for the heat pump to work at all" point. That would be interesting info to know.
Bill
I have been planning a chainsaw retrofit with a building scientist. I thought I understood him to say that if we follow all his suggestions (he gave an extensive list), the house will become very tight, and it will no longer be safe to use combustion appliances such as our oil-burning dinosaur unless we open a window. Yet you say "you dont have to decommision the old heating system after all"...?
Your building scientist is correct. If the house is tight enough, the old oil dinosaur will not operate properly, because it doesn't have enough combustion air. Opening a window (or ducted vent...) will give it enough air to breathe. I would also be concerned about the exhaust vent for the oil system. That's a big hole in the building envelope, all the time. You would also still have a tank of toxic waste in your house (the oil) that takes up space and smells bad. All of this just for the off chance that we get another weather system that doesn't happen for 50 years or so. Seems like a bad idea to me. I agree with Bill about not decommissioning when retrofitting in a new ASHP, but if you're doing a major renovation/upgrade, I would say lose it.
Makeup air is a different story. You'd either need a sealed combustion heating system (which has it's own intake for outside air for combustion), or you'd need a way to allow makeup air into the space with the old unit. It is true that very tight houses don't bring in enough air for "natural draft" type combustion appliances to work.
Bill
Agreed. If you have a tight house, you need an HRV or ERV system with properly located intake and exhaust heads and intake and exhaust openings in the building envelope to change the air periodically. You generally want supply air blowing into living areas, and exhaust air being sucked out of the high humidity and odor producing kitchen and bathrooms. There are many different configurations. If you don’t have one you will be living in a very unpleasant. jungle. I would not want a furnace or boiler sucking O2 out of the house interior for combustion air. I would say if you cannot bring combustion air from outside without causing an air leak, get rid of the old furnace. That could also apply to a conventionally vented HWH. The work around for that is to use an indirect HWH off the boiler or a tankless condensing HWH, which brings combustion air in from the outside. Wall-mounted condensing boilers and modern floor-mounted boilers like the Weil-McLane GV-90 cast iron condensing boiler also bring combustion air in from outside. The HRV/ERV make the house comfortable and prevent mold and fungi. Using outside air for combustion keep you frm dying of CO poisoning.
In general, peak grid load is not in the winter, and if in the distant future that does become the case, grid operators will have managed the change.
There are people in Canada with heat pumps and they seem to function pretty well. It becomes a building envelope issue, even in my Pretty Mediocre House, it takes hours for the room temperature to drop noticeably in a power outage and I cannot see a situation where it would drop below the high 50's with no heat whatsoever in an overnight situation.
Peak load in cold climate areas without a lot of air conditioning in the summer could be in the winter. The building envelopes in Canada are probably better, and the Maritimes don’t get very cold. ALOT of people in New England and Canada have wood or pellet stoves as primary or backup heat appliances. They sre relatively cheap to buy and install, and many have the ability to bring in outside combustion air. They also give off a pleasant heat. You can get a full skid of pellets put in the bed of your truck and unload them into the house at your leisure. Very few moving parts and no electronics to get out of whack.
Electric resistance backup, if employed on a large scale (such as lots of people switching away from gas/oil to heat pumps), would stress the power grid even more, so there are other problems with that as a backup heat source.
Hmmmm... sort of like if everyone were to switch to electric vehicles? It never made sense to me why the government pushes so hard for this shift knowing the grid couldn't keep up.
Just a rant sorry to derail the thread
I think we were at the limit of our system at -19°F. The point where we start losing ground is around -8 to -10°F due to the radiant heat loss. Even oversize doesn't compensate when the system is at its engineering limit. We are just fine down to 0°F, but if the wind is blowing the heat loss goes up faster than temperature increases can compensate for. An improved shell is really needed. Our 99% temperature is probably around 0 to -5°F. In the mountains the available weather data doesn't reflect local variation very well. The extreme lows seem to be getting more frequent.
We got -12.f in MA. Here's some pics from ecobee showing the temps in my house and the 2 Fujitsu I had running. I wish ecobee graphs showed each room sensor like they used to.
The room with the 12k Fujitsu head that should be oversized for design temps and heating held well but did drop 2f below set point.
My 18k Fujitsu Slim duct once it got near the worst point of the night (got to -12.1F and real windy) did start dropping more and the oil heat kicked (orange blocks on pics). Once the oil heat kicked it up to set point the Slim duct seemed to hold steady. -12 is below what the slim ducts are rated for nevermind my design temp I didn't oversize for in my Manual J
1st floor I won't include because the heat pump was off and pellet stove was cranking to it's set temp.
Ignore the set temps...that's the oil heat set temp...but you can see how the mini splits dropped and followed outside temp eventually.
The Fujitsu airstages at my house kept setpoint (68) to about -10f and then started to lose the battle. Two were running at full tilt - compressors at 100% no modulation whatsoever- each is 3 tons and were using 4.5 to 5kwh each and were producing 100-105 degree discharge air at the registers- those are 1:1 indoor air handler units. The other two (identical) sort of went into a limp mode and ran at 1.5- 2 kWh each blowing lukewarm air. Later as the temps went up this morning both started working again so I assume some outdoors are more sensitive to cold than others depending on myriad of factors.
So, in a nutshell- I have 4 identical 3 ton outdoors and they kept up to about -10 outdoor at which point two could t keep with set temps and the other two went limp.
This is an 8500 sq feet contemporary built in the late 80ties zone 5 with large open spaces, 25 feet ceilings, huge double pane windows and decent insulation with meticulous sealing. Yesterday for the 24 hour period I used approx 150kwh for heating which is still way cheaper than what I have used with oil during subzero temps in the past (I have a lot of historical data)
So overall- very happy.. at 30 cents per kWh oil must be at $2/ gal to break even- oil currently is just over $4 here.
Can you get an airstage with a base pan heater?
Mine have pan and compressor crank case/ band heaters have been watching their operation- definitely Smart Control- each runs anywhere between zero and 75 watts during freezing weather.
What are your indoor/outdoor model numbers? Thanks!
The outdoors are AOU36RLAVM - I have 4 of them - 2 are blowing into 1:1 ARUX24TLAV2 air handlers, one blows into ARUX36TLAV2 and the fourth one is connected to 5 indoor ceiling cassettes of the AUUA4TLAV1 type ranging from 4 to 12k BTU each. That one actually was short on gas as at 100% compressor was not able to reach 425 psi on the high side which is what they target in heating mode (Mitsus are a tad lower 410 psi)
At -10 the air handlers were delivering 100-105F discharge temps and the cassettes were running even hotter - 110-115F. Come to think of it - the air handlers always deliver about 95-105 regardless of outside temps, while indoor heads deliver much higher temps - 110-130 or thereabouts.
I am impressed, but more importantly I know now at what outdoor temp my system becomes insufficient and I have configured the backup oil heat as needed now.
I'm north of Worcester MA and Ive never seen ice in my base pans. Have 3 Fujitsus (one is a slim duct without basepan heater) at my house and used to have a Mitsubishi. I've honestly never seen ice on the coils when they defrost either. I'm up on a hill with some wetlands behind. Must be in a sweet spot with low moisture.
Greenright,
How do you determine that the units are running full tilt vs modulating? Just based on power use?
When you talk about each units 'use,' are you actually referring to an instantaneous power reading (kW) or just giving the energy use for a 1 hour window (kWh)? (Acknowledging that if power use was perfectly steady for 1 hour it's essentially the same thing)
I have a dedicated Emporia Vue V2 monitoring for my air handlers and outdoor units. So yes- I assumed they are running at 100% as there was no fluctuation of power used and it was pegged to 4.5-5KW for extended periods of time (hours) interrupted only by the occasional defrost (every 180 minutes or thereabouts as the other requirements for dynamic defrosting were not met so it defaulted to 180 minutes).
For comparison it is 32F now and they are loafing at 2-2.2kw each and their power curve is a nice wavy patter repeating every 5-10 minutes.
My MRCOOL DIY 36k btu 3-zone minisplit (with only 2 heads installed) did great in one zone, but the other - our main living area, entry, and kitchen/dining room - is just too big for one 12k head. We have another 9k btu head for the kitchen/dining room that should be sufficient. We have also been using the wood stove in the living area and a space heater in the kitchen. And wearing lots of sweaters!
Also in MA where it was -12 last night. We have a 30K Mitsubishi for the whole house with a supplemental 18K downstairs. As these are hyper heat systems they seemed to function fine however the heat load was a little too much for them overall. The thermostat was set to 64 overnight and the temp indoors got down to 62. Nothing serious and we are still adding insulation outside so by the time we are done we should not have a problem keeping the thermostat at 66 degrees or higher.
Richmass,
What is the size of your house?
Steve
House is 1800 sq. Ft. Front of house is under construction....
The temperatures around here never got below -5F so not a real test for my Fujitsu units.
However, while there is a lot of discussion of low temperatures in this thread, I think that wind and moisture (sleet and snow blowing on outdoor units) may have bigger impacts on performance than people think. This is why I never understood why outdoor units are typically installed in wide open places without any wind protection or cover from precipitation. The manufacturer mandated spacing requirements for air circulation are pretty forgiving so I suggest folks consider this when placing the outdoor units. This is why I placed my units under an 8 ft high deck with the prevailing wind blocked by the house and some large evergreens. My units have the proper air spacing mandated by Fujitsu but never get wet and rarely experience direct wind. I think that has helped. The two older units have performed well for 8 years now. The new one is doing well too.
Nick,
In what way would wind reduce efficacy?
The refrigerant is colder than outdoor air, picking up heat from the air-- the opposite of a warm body losing heat to the wind. But I may be missing part of the equation?
That is a good question. I do not know the exact physics; perhaps some of the more scientific folks can weigh in. I am going on observations over the ten or so years we have had mini splits in several houses, including a few on the Jersey coast where there are strong prevailing winds.
I recall a thread a while ago where Dana Dorsett suggested that a combination of wind and snow/sleet could increase defrost cycle frequency, which could impact performance. I have also read articles that claim a micro climate can be formed around an area that is protected from the wind, slightly increasing the temperature of the air hitting the coils and therefor improving peformance (but then you wonder whether the lack of sun in a protected location could have the opposite effect on cold sunny days). I think the impact may be more pronounced on days when the wind blows directly into the outdoor unit, which may impact the work of the fan to draw air across the coil.
Fujitsu offers a wind baffle and suggests in its catalogue that the baffles will ensure "continued operation in high wind conditions, especially in roof mounted units"; they will "prevent nuisance stoppage of outdoor units if wind gusts reverse fan rotaton while the fan motor is off" and suggest they will "prevent snow from accumulating in the outdoor unit [and] causing performance issues".
Of course, high winds may be drawing heat from a leaky house so that certainly has an impact on performance....... but that is a different matter altogether.
"could increase defrost cycle frequency, which could impact performance."
Ah that makes sense. Especially moisture, and I suppose wind could help drive more moisture into the coils.
And the wind blowing against the fan also makes sense.
Yes, my units that are protected under the deck never get wet or covered in snow and I have never had a problem with icing in the 8 years they have been running in winters.
Not sure about the exact reason but https://www.energy.gov/energysaver/air-source-heat-pumps says it's defrost-related
Hmm. The way they phrase it,
it almost makes it sound like it IS an issue with the heat being whisked away, which I implied isn't a problem when the coils are colder than air, but during defrost when they are warmer perhaps it is.
Interesting. On the other hand, since I use my mini splits 90% for heat, I have wondered about placing one unit against my south facing wall and putting a reflective curtain around three sides to see if I could heat the air around the unit during the many winter days that are cold but very sunny. I could then see if that improved performance on such days versus the identical unit under the deck in the shade.
I was watching this video https://youtu.be/fxEqVuiHhM0 and a few thoughts occurred;
What you're saying about the defrost cycle makes the most sense. Another less important factor might be on days where the air can carry more moisture but it's still cold enough to require defrost cycles, maybe that extra air movement ends up being a net higher moisture load.
The weather plays a huge role. I have done some tracking and I can tell you that my Airstages will defrost at the longest interval 180 minutes when cold and dry (below say 24f and 30% RH) while when just above freezing when raining or sleeting the outdoors get plugged with ice every 30 minutes or so forcing defrost cycles. My defrost cycles are usually around 3-5 minutes each. That is 10 minutes of each hour spent spinning the compressor to max, but no heat. That is roughly 20% loss of heating capacity due to defrost every hour
We were discussing above whether protecting the outdoor condenser from rain or sleet improves efficiency by reducing defrost cycling? Are your units fully exposed or under a protective cover?
They are on the prevailing downwind side of the house so they dont get stuffed with snow/rain/sleet. But when precipitation falls down it falls down vertically where they are. So around freezing when precipitating the outdoors were getting stuffed in with ice very quickly (20 mins on average between defrosts). I installed small overhangs extending about 5-7" over the rear edge of the cabinets (sheets of styrofoam with a small weight on top to prevent movement). The fan action still draws some ice in from behind, but it is far less and my defrosts are further apart (about 1 cycle per 1.5 hours). Once the weather improves I will most likely install something more permanent and extend the lip further out, but for now it works very well as is.
We have a 4 ton Carrier Central unit in about 2800 Square feet with a 26 foot vault in part of the house. We hit -9F with 40 mph winds and the backup electric kicked on twice for about 20 minutes each time. Other than that the Heat pump has handled everything since it was installed about a year and a half ago without backup. Design temp was zero.
Would you mind sharing the part numbers of the units and the design heat load for your home?
We measured -22F in Sunapee, NH (1,400 feet) at around 5am.
Here is what I observed with our singular, one ton mini split heat pump (Fujitsu). No back up heat.
1. Unit never shut off. However, occasionally, a green light would blink and the fan would stop.. It would resume operating after a few minutes. It never went into 'turtle mode'.
2. The air from the cassette felt only slightly warm to my skin. (Plenty to heat, but not "hot")
3. Temperature in house was 2 degrees lower than our set temperature.
4. Unit was on "energy saver mode".
I dropped to -5 and my 2 12k btu Gree Sapphire single zones were still pumping their full capacity.
I monitor the electricity and delta T across the coil so have a good real time cop. A proper unit with enchanced vapor Injection will produce heat even at insanely low outdoor temperatures.
What do you use to constantly measure delta T?
Deleted
Hey, I live in south coastal Maine and kept my eye on the weather during the sub-zero temperatures which you referred to. I switched to auxiliary heat in advance. I usually turn off my heat pump and switch to the gas fired boiler when the outside temperatures are expected to be less than +10°F for more than a couple of hours. So, to your question... My heat pumps just don't work well at all when we get to single digit temperatures. My mini-split heat pumps are only a few years old and sold as "Hyper-Heat" which should be producing some heat down to about -1o°F. They don't.
More recently, on 25-Feb, we had some temperatures at around +5°F through the entire night. I left the heat pumps running so that I could gather some performance numbers. By 6 AM the inside temperatures were lagging by about 4 degrees from the set point. Importantly, the room was uncomfortably cool and noisy with high fan speeds; it also had frequent defrost cycles which resulted in a lot of temperature variation. In late morning the sun came out and the heat pumps brought the inside temperatures back to the set point.
These heat pumps are a source of endless disappointment for me. I recently configured my thermostats to automatically switch to auxiliary gas heat according outside temperatures below +10°F.
What model is your heat pump?
Sounds like a problem with the install, you most likely have a leak and the system is low refrigerant.
Hey Akos, I have a Mitsubishi MXZ-3C30NAHZ2-U1 with three inside wall units.
Indeed it does sound like a problem with the install, configuration, or just simple mechanical failure or defect. The likelihood of a leak is low. That was already considered and probably is not the case. The system was on the "low" end of the acceptable range; additional refrigerant was added to bring it to the upper end of the range. The performance is still poor.
If you look at the specs of the 3c30:
https://ashp.neep.org/#!/product/67773/7/25000///0
It will deliver full rated output at 5F, that means it should be blowing nice hot 110F or so air. If your unit is blowing warm air, there is a problem with it.
I don't know how "considered and probably not the case" of the leak but I'm pretty sure they are wrong. The only way to check the refrigerant on these is by reclaiming and weighing it, no way to know if it is near the upper or lower end of the range by measuring pressure. Randomly adding refrigerant to these does not work.
The only way a new install is on the low end of the range is if there is a leak or if you have very long line sets and the correct additional refrigerant was not added in the first place.
Besides low refrigerant, the only other option is kinked line sets. This is surprisingly easy to do but at least some of your indoor head should still work well.
You need the tech that installed it to come, reclaim and weight the refrigerant. If it is low, it means there is a leak, don't just top it up as you'll have the exact problem next year. The leak needs to be fixed and the system filled to the required weight. If you get pushback, I would talk to Mitsubishi. The install has a defect, it should not be your problem or cost.
MattyT, who was the installer (I'm in Maine as well as you can guess from my screen name).
What I wonder is if an experience like yours is due to improper system install/configuration, or an inherent tech failing. There are enough stories of these systems working properly, well below the temps you mention, to beleive that something is off when they don't work as you describe.
Have you monitored energy usage as well?
If these heat pumps used a rebate from Efficiency Maine, I recommend sending a comment to them informing them of your experience. They need to know if installers are messing up. I tried to ask if they are aware of how many systems are being installed with poor performance due to improper sizing, etc. and their answer was very bureaucratic. The more they hear their 'certified' installers don't know what they're doing, the better.
Hey Tyler, I live south of Portland. My system was installed by a local Diamond Elite contractor in the Scarborough area.
Yes, I do monitor usage but only on the monthly utility gas/electric bills. I don't actively monitor the usage beyond the bill. I would say that the system probably saved me a small amount in energy costs over the past four heating seasons. However, the saving is pretty small by comparison to the cost of the system. Recent rate hikes for electricity will probably diminish the savings even further. My gas boiler is fairly efficient which makes it hard for a poorly functioning heat pump to net out any savings.
It is interesting that you contacted Efficiency Maine. In fact, I did contact them about the issue and they never responded. In the past, I've had concerns with their bureaucratic replies too. Some of their replies make absolutely no sense. It is clear that they are only motivated by installations which net out rebates. That's how they make their money to keep their "non-profit" afloat. Efficiency Maine needs more skin in the game when systems and contractors (which they referred me to) don't perform as expected. Because of their lack of response, I am now inspired to follow-up with Maine's consumer protections. Also, I found that Maine Public Utilities Commission has oversight responsibilities on Efficiency Maine. Perhaps that might be another angle for us toward resolution. Also, you should check Maine's Implied Warranty statute on the Maine Attorney General's website. It definitely applies to heat pumps.
Thanks for your question. The replies are helpful.
"It is clear that they are only motivated by installations which net out rebates. That's how they make their money to keep their "non-profit" afloat."
I will admit to being a bit confused by this. My understanding was that Efficiency Maine (trust) was a quasi governmental agency responsible (among other things) for managing/distributing various government or grant cash incentives. I did not think they made any money on rebates. (?)
My sense--when I probed them about how well-monitored heat pump installations were-- was that they weren't bothered by small details like installers not understanding how to optimize installations. They're a big organization that has lofty goals, and I suspect they just don't really care about numbers on the ground to that level of detail. Perhaps so long as there is net gain by pushing lots of heat pump installs. Which is kind of fair, but a bit of an issue if an actual high percentage of heat pump installs are running much more inefficiently than they should be (which is kind of my sense).
They made this claim:
"we evaluate rebated heat pumps very carefully. We inspect thousands of rebated installations every year and we hire third party auditors to very carefully evaluate installations including metering to determine actual performance."
Which sounds good, but I question how accurate or detailed a picture they really get.
I guess I need to rethink my HVAC for my new house I am building near Bridgton… I was planning on using a hyper heat with a wood stove back up, but now I’m a bit worried.
Steve
Steve,
To be clear, I don't have a handle on what it's like out there. I mainly am judging based on how common multi splits are and that in my area, the local installer isn't doing sizing calcs. For the rest of Maine and beyond, I'm just guessing. I'm definitely not trying to scare people away from mini splits, as they can definitely work. You may just want to consider pushing your installer a bit to do load calcs and perhaps (depending on your situation) push for 1:1 units vs multis.
Two hyper-heat compressors serving six heads, running during the one cold snap this past winter, in the Mount Washington Valley. One ran just fine; one had cycles of cold air. Temp below -13F for maybe twelve hours, to -17F at the coldest. It's a new house, insulated with Zip-R(6), and closed cell foam- 3" in the walls, and 6" under the roof. We opted for resistant electric baseboard in the bathrooms for peace of mind, and a propane woodstove in the main living area. Running the propane and not the electric resistant heat, bottom line we stayed comfortable.
Who retitled this question? It makes no sense.
The question was during an arctic blast of (in my case) -19 (NEGATIVE 19) degrees Fahrenheit.
If GBA is retitling posts for SEO, they should at least pay a bit more attention.
I wish they'd pay more attention to spam and less to thread titles.
At neep.org there is a great resource for these kinds of discussions. Select a heat pump*, put in your zip code and heating load, and it produces a great report showing how that heat pump will perform in your climate. I'm going to try and attach a screen shot.
*(unfortunately you have to select the heat pump, what would really kick is if you could just put in your zip code and heating load and it would find heat pumps for you.)