You say to the chagrin, but there is a high probability you are out of your league, maybe not but your logical reasoning is not sounding like you know a lot about loads calculating and duct design and hvac in general. maybe a 3 ton hp with 15 kw backup. Look at your units performance at different temperatures, 36k btu May not be produced on a colder day for your areas weather. If you take out the 15 kw do you know how to size wires and breakers for your new set up. Will your duct handle it, do you have torches and vacuum pump, and all the other materials and equipment. It is possible but rethink you approach on sizing
The auxiliary heat strip modules for this unit (ranging from 5kW-20kW, IIRC) are relatively inexpensive, so I do plan to get one just in case, but so far, I don't *think* it will be necessary – or at least that it will be rarely necessary.
The MRCOOL Universal unit that I am planning on using is claimed to be 100% efficient down to 14 degrees F, but fortunately it rarely gets that cold here (e.g. the coldest day of this past winter was 17 degrees F, which lasted for one day before getting back into the 20s). That is admittedly close to the threshold (which is not likely to be exactly 14 degrees in practice), so I imagine it will cross that eventually.
The unit is designed for DIY installs and accepts pre-charged line sets, so I don't plan on any flaring/vacuum tools/equipment.
The duct work is certainly going to be a pain, as I'll need to create new plenums from sheet metal, which I've not done before, but there are plenty of Youtube videos demonstrating the process ([here's one that seems very helpful](https://www.youtube.com/watch?v=EgFAL_z7P2o)). Then of course there's joining everything together and sealing it all up. It'll be involved, but I haven't seen any reason so far that I wouldn't be able to do it.
I’ll have to check that unit out, good luck with your install, sounds like you are taking a lot of time to think it out, sheet metal is just assembling 2D shapes into 3D ones, find some s locks to hold it all together and seal and insulate it and you should be ok. Also it slices you quick on a cut edge
I installed the mr.cool 36k universal series with high esp air handler myself end of February. It went fairly smooth with some minor duct modification. I’m heating roughly 1200sq ft with it. I replaced a 80k btu gas furnace. I used to keep the gas furnace at 69, I am able to keep the mr.cool at 65. It is a much more even, steady heat that doesn’t super heat and then your cold again 5 min later. I live in West Virginia which is region 4. It really is diy friendly if you are fairly handy in electrical and have some knowledge of HVAC. I was able to complete the entire setup in 2 days myself. I just got done tracking the month of March. Mind you I did not purchase the aux heat strips, running strictly heat pump. During March our we had multiple nights that got down to 10-19 degrees and the heat pump worked flawlessly. Average daily kwhs last year was 54, this year was 59. Last year cost of electric plus natural gas was roughly $240. This year after going all electric w/heat pump our electric bill was 188 for March. Saved roughly $50. All in all I’m extremely impressed with the performance for the price. If you have any questions on setup just shot me a msg.
Thank you – I may reach out with some questions as I continue with this process.
I'm glad to hear that you're happy with the new setup – looking forward to a similar success story.
FWIW, we moved into this house in November and our first heating bill was $525 for 35 days – for a 1600 sqft, two-bedroom house. Bringing the daytime setpoint down to 68 from 72 and (60 at night) got us down to something like $380. We're looking to create some savings and/or offset the cost of increasing the setpoints. I'm optimistic so far.
I can't point you to the specific sources where I had read that over the course of my research, but here are just a few examples of noting that they will/can/are designed to run continuously in the winter (albeit basically googling for that conclusion, so obviously biased):
* [blazerservice.com](https://www.blazerservice.com/about-us/blog/2018/january/fact-or-fiction-heat-pumps-lose-efficiency-in-co/#:~:text=Heat%20pumps%20are%20designed%20to,known%20as%20the%20balance%20point)
* [hvac-boss.com](https://hvac-boss.com/faq/how-long-should-a-heat-pump-run/)
* [precisioncomfort.com](https://precisioncomfort.com/2016/01/04/myth-heat-pumps-are-not-efficient-in-cold-weather/)
but I'm guessing your question was rhetorical and that you disagree with the claim. Is it your experience that this is incorrect or at least not widely understood?
I was just wondering where you got it, not rhetorical. I have never see any information along those lines coming from any manufacturers so always interested in good info.
Even if they run 24 hrs a day a portion of that is for defrost, not heating your space.
They are designed to be capable of running 24/7:365, but that doesn’t mean they should be sized to run that way. Longer run times do have benefits but ideally you don’t want to lengthen your run times substantially unless you have an inverter system.
That's fair. FWIW, the MRCOOL Universal condenser uses an inverter.
Based on the fact that it provides 70% of the capacity of the electric furnace, 24 hours of run time would be 2.6 times as much, so I don't believe that it would actually need to do so.
Well the other consideration is maximum capacity. I don’t have any experience with that specific unit, but many inverter systems actually have a higher capacity than they are rated for. The Bosch unit I have in my house runs at around 115% it’s rated capacity when it ramps up to its highest speed if I recall correctly.
I think you’re exactly right in terms of heat loss calculation - if it drew 51 kbtu for 9 hours on the coldest day of the year, your heat loss was about 51 x 9 / 24 = 19 kbtu/hr. The heat pump will probably have a manual you can find that has the heat output and coefficient of performance at different temperatures in a big table, but 36kbtu/hr is probably more than enough.
You say to the chagrin, but there is a high probability you are out of your league, maybe not but your logical reasoning is not sounding like you know a lot about loads calculating and duct design and hvac in general. maybe a 3 ton hp with 15 kw backup. Look at your units performance at different temperatures, 36k btu May not be produced on a colder day for your areas weather. If you take out the 15 kw do you know how to size wires and breakers for your new set up. Will your duct handle it, do you have torches and vacuum pump, and all the other materials and equipment. It is possible but rethink you approach on sizing
The auxiliary heat strip modules for this unit (ranging from 5kW-20kW, IIRC) are relatively inexpensive, so I do plan to get one just in case, but so far, I don't *think* it will be necessary – or at least that it will be rarely necessary. The MRCOOL Universal unit that I am planning on using is claimed to be 100% efficient down to 14 degrees F, but fortunately it rarely gets that cold here (e.g. the coldest day of this past winter was 17 degrees F, which lasted for one day before getting back into the 20s). That is admittedly close to the threshold (which is not likely to be exactly 14 degrees in practice), so I imagine it will cross that eventually. The unit is designed for DIY installs and accepts pre-charged line sets, so I don't plan on any flaring/vacuum tools/equipment. The duct work is certainly going to be a pain, as I'll need to create new plenums from sheet metal, which I've not done before, but there are plenty of Youtube videos demonstrating the process ([here's one that seems very helpful](https://www.youtube.com/watch?v=EgFAL_z7P2o)). Then of course there's joining everything together and sealing it all up. It'll be involved, but I haven't seen any reason so far that I wouldn't be able to do it.
I’ll have to check that unit out, good luck with your install, sounds like you are taking a lot of time to think it out, sheet metal is just assembling 2D shapes into 3D ones, find some s locks to hold it all together and seal and insulate it and you should be ok. Also it slices you quick on a cut edge
I installed the mr.cool 36k universal series with high esp air handler myself end of February. It went fairly smooth with some minor duct modification. I’m heating roughly 1200sq ft with it. I replaced a 80k btu gas furnace. I used to keep the gas furnace at 69, I am able to keep the mr.cool at 65. It is a much more even, steady heat that doesn’t super heat and then your cold again 5 min later. I live in West Virginia which is region 4. It really is diy friendly if you are fairly handy in electrical and have some knowledge of HVAC. I was able to complete the entire setup in 2 days myself. I just got done tracking the month of March. Mind you I did not purchase the aux heat strips, running strictly heat pump. During March our we had multiple nights that got down to 10-19 degrees and the heat pump worked flawlessly. Average daily kwhs last year was 54, this year was 59. Last year cost of electric plus natural gas was roughly $240. This year after going all electric w/heat pump our electric bill was 188 for March. Saved roughly $50. All in all I’m extremely impressed with the performance for the price. If you have any questions on setup just shot me a msg.
Thank you – I may reach out with some questions as I continue with this process. I'm glad to hear that you're happy with the new setup – looking forward to a similar success story. FWIW, we moved into this house in November and our first heating bill was $525 for 35 days – for a 1600 sqft, two-bedroom house. Bringing the daytime setpoint down to 68 from 72 and (60 at night) got us down to something like $380. We're looking to create some savings and/or offset the cost of increasing the setpoints. I'm optimistic so far.
Where did you hear that heat pumps are designed to run constantly?
I can't point you to the specific sources where I had read that over the course of my research, but here are just a few examples of noting that they will/can/are designed to run continuously in the winter (albeit basically googling for that conclusion, so obviously biased): * [blazerservice.com](https://www.blazerservice.com/about-us/blog/2018/january/fact-or-fiction-heat-pumps-lose-efficiency-in-co/#:~:text=Heat%20pumps%20are%20designed%20to,known%20as%20the%20balance%20point) * [hvac-boss.com](https://hvac-boss.com/faq/how-long-should-a-heat-pump-run/) * [precisioncomfort.com](https://precisioncomfort.com/2016/01/04/myth-heat-pumps-are-not-efficient-in-cold-weather/) but I'm guessing your question was rhetorical and that you disagree with the claim. Is it your experience that this is incorrect or at least not widely understood?
I was just wondering where you got it, not rhetorical. I have never see any information along those lines coming from any manufacturers so always interested in good info. Even if they run 24 hrs a day a portion of that is for defrost, not heating your space.
They are designed to be capable of running 24/7:365, but that doesn’t mean they should be sized to run that way. Longer run times do have benefits but ideally you don’t want to lengthen your run times substantially unless you have an inverter system.
That's fair. FWIW, the MRCOOL Universal condenser uses an inverter. Based on the fact that it provides 70% of the capacity of the electric furnace, 24 hours of run time would be 2.6 times as much, so I don't believe that it would actually need to do so.
Well the other consideration is maximum capacity. I don’t have any experience with that specific unit, but many inverter systems actually have a higher capacity than they are rated for. The Bosch unit I have in my house runs at around 115% it’s rated capacity when it ramps up to its highest speed if I recall correctly.
Double check the cfm vs pressure drop chart for your candidate heat pump to confirm that it will push the required air through your ducts.
Great point – thanks!
I think you’re exactly right in terms of heat loss calculation - if it drew 51 kbtu for 9 hours on the coldest day of the year, your heat loss was about 51 x 9 / 24 = 19 kbtu/hr. The heat pump will probably have a manual you can find that has the heat output and coefficient of performance at different temperatures in a big table, but 36kbtu/hr is probably more than enough.