Bosch Heat Pump Experience?

[antonca]

I am currently heating my 2400 sq ft house with wood (Buck 91)/oil/heat pump (Trane). To offset the cost of oil and use less wood this year I have dropped the crossover outdoor temp of my heat pump to 20 degrees. Its keeping up for most part down to these temps but have hear Bosch Inverter Duct Split (IDS) can run down to 5 degrees effectively. Has anyone ran this model down to these temps or lower than 20 degrees?

Debating on replacing my heat pump for Bosch that claims to function in lower temps in hopes to offset the cost of oil....but don't want to waste my $$$$!

Thank you!

 

[begreen]

My understanding is that Bosch is using Mitsubishi's inverter compressor for their systems. The last time I looked the Bosch systems were limited in sizing and did not have a 4-ton which is the size our house would need, but that was a while back.

 

[antonca]

My understanding is that Bosch is using Mitsubishi's inverter compressor for their systems. The last time I looked they were limited in sizing.

Thanks good to know. The largest I believe available is 5 ton

 

[begreen]

Yes, they had a 3 and a 5 ton, but that was a while ago. They may have 4 ton now? What I am not certain of is what value the Bosch system has over a Mitsubishi or Daikin equivalent.

 

[stoveliker]

My Mitsubishi minisplit can do this (and has kept me warm at 20 F, I did that as a test).

There are also hyper heat systems that can go at even lower outside temps.

 

[peakbagger]

Not specific to Bosch but be careful on Hyperheat or cold climate "mini split"heat pumps. The selling point with these units are that can put out heat down to minus 12F or lower at full output and technically that is true, but the efficiency drops precipitously below 20 degrees down to the point where the unit is no better than an electric heater. The resultant heat produced is lower quality, the unit may be only heating the return air a couple of degrees when very cold so it has to move a lot of air and depending on the weather outdoors, it may be going into defrost frequently which is noisy and drafty. If your house is in an area that rarely gets below 20 F a hyper heat unit still has better effficiency than standard units but if you consistently go below 20 F make sure you have backup heating system that is burning something other than electricity.

 

[stoveliker]

The cop for e.g. model MXZ-4C36NAHZ
at 17 deg is still larger than 2.5, so the power used vs heat delivered is still 2.5 times better at this temperature below 20 F.

Of course that is indeed less efficient than at higher temps, but your remark about electric heaters is incorrect at least for 17 F temps. I don't have data for lower temps

 

[EbS-P]

What seer or hspf rating is the heat pump and what size is it? Is the ductwork in good shape and well sealed? How good is your insulation? How well air sealed is the home? How many heating degrees days and cooling do you have? What’s your cost of electricity? Do just want to save money or is being green important to you? How many people live at home? How are you heating water?

all these things should be considered when considering energy saving upgrades.

 

[begreen]

I am currently heating my 2400 sq ft house with wood (Buck 91)/oil/heat pump (Trane).

Which Trane system do you have? I am exploring a similar question with our 16 yr old American Std Heritage 16 system. It was a very high-efficiency, 2-stage unit in its day. This system and the almost identical Trane units were the only ones available in this efficiency range for a ducted system back then. Now there are a lot more choices and I will be exploring upgrade options to an inverter system like you are, but not sure how much real gain I would see. Our system has an HSPF of 10 and can heat the house well down to about 35º, the changeover to resistance coils is at 25º.

 

[EbS-P]

Which Trane system do you have? I am exploring a similar question with our 16 yr old American Std Heritage 16 system. It was a very high-efficiency, 2-stage unit in its day. This system and the almost identical Trane units were the only ones available in this efficiency range for a ducted system back then. Now there are a lot more choices and I will be exploring upgrade options to an inverter system like you are, but not sure how much real gain I would see. Our system has an HSPF of 10 and can heat the house well down to about 35º, the changeover to resistance coils is at 25º.

Is yours a split coil system or a package unit?

 

[begreen]

It's a 3-ton split system with a DC variable speed air handler.

 

[EbS-P]

I am currently heating my 2400 sq ft house with wood (Buck 91)/oil/heat pump (Trane). To offset the cost of oil and use less wood this year I have dropped the crossover outdoor temp of my heat pump to 20 degrees. Its keeping up for most part down to these temps but have hear Bosch Inverter Duct Split (IDS) can run down to 5 degrees effectively. Has anyone ran this model down to these temps or lower than 20 degrees?

Debating on replacing my heat pump for Bosch that claims to function in lower temps in hopes to offset the cost of oil....but don't want to waste my $$$$!

Thank you!

Check the specs of the unit here.

ASHP

ashp.neep.org

 

[begreen]

I'd need to dig up the condenser and air handler model numbers to do that. I seem to recall it has and HSPF of 10, but not much else.

 

[EbS-P]

I would recommend to anyone who doesn’t absolutely have to replace a hvac equipment to wait. We don’t know the efficiency that IRA rebates and or credits will apply to. Second 410a will be completely phased out of new equipment soon. ( maybe that’s a reason to buy sooner). And when it comes to paying more for higher efficiency. If you’re burning wood you are extending that ROI timeframe considerably. Last time I ran the numbers (and I’m going to use SEER because it’s how they are marketed). There was no way that I could recoup the cost difference for a top end 22 SEER unit vs a 16. (Based on my three ton unit).

We will get the minimum rating for the government supplement soon and what the incentives are And that will likely influence many decisions.

 

[begreen]

I would recommend to anyone who doesn’t absolutely have to replace a hvac equipment to wait. We don’t know the efficiency that IRA rebates and or credits will apply to. Second 410a will be completely phased out of new equipment soon. ( maybe that’s a reason to buy sooner). And when it comes to paying more for higher efficiency. If you’re burning wood you are extending that ROI timeframe considerably. Last time I ran the numbers (and I’m going to use SEER because it’s how they are marketed). There was no way that I could recoup the cost difference for a top end 22 SEER unit vs a 16. (Based on my three ton unit).

We will get the minimum rating for the government supplement soon and what the incentives are And that will likely influence many decisions.

Definitely waiting until at least 2023. And yes, I figure the unit has had a relatively easy life so its longevity is hopefully extended. Still, 24/7 heating with wood is going to be more of a challenge as time goes by, so if the price is good and the tax options work, then I may go for it.

 

[EbS-P]

The Bosch units are not priced like top end Trane or Carrier units

5 Ton Bosch 18 SEER2 Inverter Compressor Heat Pump DOWN-FLOW or HORIZONTAL Package Unit BRBA-60HWD1N1-M18

The Bosch 18 Seer 3.5 to 5 Ton Inverter Compressor Heat Pump package unit achieves 11.2 EER2 and 9 HSPF2 ratings while being completely convertible to downflow or horizontal airflow configuration. The Compressor operates from 25% to 110% capacity. The BRB-60HWD1N1-M19 Comes with a 10 year warranty!

www.budgetheating.com

American Standard 14 seer 5 Ton Heat Pump Packaged Unit - My HVAC Price

4WCC4060A

myhvacprice.com

 

[antonca]

Which Trane system do you have? I am exploring a similar question with our 16 yr old American Std Heritage 16 system. It was a very high-efficiency, 2-stage unit in its day. This system and the almost identical Trane units were the only ones available in this efficiency range for a ducted system back then. Now there are a lot more choices and I will be exploring upgrade options to an inverter system like you are, but not sure how much real gain I would see. Our system has an HSPF of 10 and can heat the house well down to about 35º, the changeover to resistance coils is at 25º.

 

[antonca]

Trane XR14 here is model number: 4TWR4048G1000AA

Which Trane system do you have? I am exploring a similar question with our 16 yr old American Std Heritage 16 system. It was a very high-efficiency, 2-stage unit in its day. This system and the almost identical Trane units were the only ones available in this efficiency range for a ducted system back then. Now there are a lot more choices and I will be exploring upgrade options to an inverter system like you are, but not sure how much real gain I would see. Our system has an HSPF of 10 and can heat the house well down to about 35º, the changeover to resistance coils is at 25º.

 

[EbS-P]

How much do you heat with wood? My thoughts are these. My XL 16 unit had a cop of 4 when it’s 52 out. 3.8 when it’s 47 and 2.5 at 17.

Getting a more efficient unit that runs at cold temps really only makes sense if you use it at the cold temps. If you are burning weekends only it probably does make sense to up grade but you burn 2 plus cords a year. I’m not so sure.

I’ve not heard much about Bosh yet.

 

[Highbeam]

Not specific to Bosch but be careful on Hyperheat or cold climate "mini split"heat pumps. The selling point with these units are that can put out heat down to minus 12F or lower at full output and technically that is true, but the efficiency drops precipitously below 20 degrees down to the point where the unit is no better than an electric heater. The resultant heat produced is lower quality, the unit may be only heating the return air a couple of degrees when very cold so it has to move a lot of air and depending on the weather outdoors, it may be going into defrost frequently which is noisy and drafty. If your house is in an area that rarely gets below 20 F a hyper heat unit still has better effficiency than standard units but if you consistently go below 20 F make sure you have backup heating system that is burning something other than electricity.

The cop for e.g. model MXZ-4C36NAHZ
at 17 deg is still larger than 2.5, so the power used vs heat delivered is still 2.5 times better at this temperature below 20 F.

Of course that is indeed less efficient than at higher temps, but your remark about electric heaters is incorrect at least for 17 F temps. I don't have data for lower temps

I kept hearing this from Peakbagger and now that I have a minisplit installed I checked the numbers on my equipment which are published to earn the energy star rating. The tables are published for heating and cooling but heating is being discussed here.

My Mrcool 24k unit has a 10 HSPF but that's a seasonal specification and pretty worthless just as the SEER of 20. It is not a hyper heat or low ambient temperature appliance. Those cost more and are not DIY. This is the basic dime a dozen type that are relabeled under many different brand names.

So I had to dig into the tables and my chinese mrcool is not as good as Stoveliker's minisplit and only makes a COP of 2.0 at 17degrees F. That's considering the "Total Net Capacity" at 70 degrees inside temp which as far as I can tell includes the defrost cycles, blower motor on the inside unit, and the pan heater. Like the Total and net. Not partial or gross. Maybe Stoveliker's higher numbers skip out on some of those factors?

I sized this thing to heat my home at 5 degrees by comparing actual wood usage to the total net capacity at 5 degrees outside temperature. At 5 degrees the COP is 2.14 which also puts me at odds with some of Peakbagger's assertions. These things are moneymakers in the cold weather.

There is a precipitous drop to a COP of 1.18 at -22 F. Now, even then, it's a moneymaker compared to resistance heat but less so and the Total Net capacity at -22 F ambient is just 8110 btu per hour compared to the 22,140 btu per hour at 39 degrees ambient.

So you need to choose your design temperature and design your system to deliver enough heat at the worst case. If you want to be okay at -22 then you will be way overpowered at 5. This is when you shut off one or two of your systems because maybe just one is enough and can operate in a more efficient range.

I also did some cost per kwh math and it is NEVER cheaper to heat with the heat pump when considering my actual cost for wood. I buy logs. If I use market rate for delivered, split, wood then of course there is a cost crossing point in the mid 40sF.

 

[stoveliker]

That is not the unit I have, but one I looked at when deciding.

In the end, I had the same conclusion as you: I am better off heating with this thing when it's not very cold and use the stove when it is. Both because BTU delivery capability goes down when it gets real cold, and because the cost of a unit that can still fairly efficiently deliver BTUs when it's real cold, is rather high as compared to a more moderate temperature unit. So I got the mxz-4c36na2 rather than the ...hz.

With this unit, I didn't like hearing the gurgling when it defrosts. The sound for me equated to hearing energy being wasted. As that happened here below 35 F, I don't use the unit below 36 F. I did try it at I believe 15 F, and it still delivered enough BTUs to keep me warm.

 

[Highbeam]

Another angle, and perhaps will help Peakbagger's case is that when you get into the lower COP range that occurs down below 5 or whatever, the cost per btu goes up and may be higher than your fossil fuel equipment if you have it. The minisplit is still much better than straight electric resistance heat but there are cheaper ways to heat the home. Wood is my plan.

At COP of 1.18 at 5 degrees F and my 11 cent electric cost, a million btu costs 27$. Wood pellets at 250$ per ton costs 20$ per million btu. LPG at 2.50$ per gallon is 32$. Fuel oil at 4$ is 38$.

We have a lot of heating season, probably 50% of it, that is 35-50 degrees outside, dark, and rainy. I hope to use the mini at a slightly higher cost but at a much lower level of effort to preserve my wood stash. I think it offers better temperature control too so I don't waste energy by overheating the home. We like 80 degrees with wood but that just won't happen when burning electrons.

 

[peakbagger]

Your money, your choice. My experience with mine is anything under 20 F and its got a major comfort deficit. Part of it is that people are undersizing to average winter heat loss rather than peak heat loss. Performance on heat pumps goes down as outdoor air temps decrease, while heating demand goes up and most folks are not going to layout the extra money to deal with lowest temps. As I have mentioned before the quality of the heat produced in my opinion is subpar at the colder temps. Open up a door from the outside to enter the house and the unit struggles to catch up. From a BTU basis 1000 cfm of air heating 1 degree F is equal to 100 CFMs heated 10 degrees but most people would want the warmer air at lower air velocity. Every time there is a defrost cycle, cold air is introduced to the room that then needs to be reheated. It is not just me, my former employer had involvement with a large number of public buildings including apartment buildings and most of them are regretting going with a pure air source solution. Most are spending the money and going geothermal as a properly designed geo unit never sees the cold temps.

My observation is that folks heating with minisplits are keeping room temps higher. Drafts tend to come from the perimeter of the house while a minisplit discharges into the center of the room. Most people compensate by running higher temps than hydronic heating that is put in the room at the perimeter low point.

I have also related about a business that is doing record volume selling an installing both new and used vented kerosene (now heating fuel) heaters to folks that had gone with minisplits exclusively and are now voting with their checkbook to put in a kerosene heater as a backup.

Note, units COP at low temps are getting better. The manufacturers used to only list COPs at 46 F, they have been forced of late to list lower COPs so they are spending the time to get the low temp performance improvement.

One of members lives in CT and loves his minisplit but his seasonal temps are typically higher than 20 F. If south of the 20 F line have at it but if you live up in Northern Maine away from the coast influence than you need to look at power cost versus wood, propane or oil.

 

[stoveliker]

Not generally true for the center of the room thing. Minisplits need a line to the outside, and unless you have an attic above the room you at heating, the inside unit is on an external wall.

And for the higher temps; I keep it at exactly the same temp as any other heat. The point is to direct the airflow away from where you are. Mine is aimed at the floor directly below in winter, and along the ceiling in summer. It is perfectly comfortable.

Finally, mine heated fine at 15 F outside. I didn't notice a blast of cold air - again because it's not aimed at the couch.

I suggest that generalizing a personal experience to all cases may not be a proper reflection of the average world.

 

[Highbeam]

Performance on heat pumps goes down as outdoor air temps decrease, while heating demand goes up and most folks are not going to layout the extra money to deal with lowest temps.

Well sure, if you don't install the properly sized equipment then you will get cold when the lower temperatures arrive. This is not a fault of the equipment or technology but a failure to properly size your equipment for those conditions. This whole argument is not an argument but a realization that you have to think before you specify the equipment. The same would happen if you try and heat a mansion with a 5kw diesel heater. You can't blame the equipment for that shortcoming either.

I did the math for you to see. Fuel oil is much much more expensive in my region. Is it possible that those people buying a kerosene heater to make up for an evil undersized heat pump simply made two mistakes?

Honestly though Peakbagger, your climate is much colder than mine and I have not tried to stay warm in the teens or lower yet with the heat pump. We'll be in the low 20s this week but wood is so much better. I doubt I'll ever have as much experience as you with actually trying to heat with a heat pump in such low temperatures.

Also to be fair, as you point out, strides have been made in the technology even recently on these things to heat more effectively and efficiently and so decade old experience may no longer be applicable.