Searching for a new heat pump

[wolfonahill]

I’ve been going through some of the older threads on heat pumps and have learned quite a bit- still unsure of some things though...

In Southeastern PA, we heat our 1400 sqft ranch house primarily with a Hearthstone Clydesdale insert. As a backup we have been nursing a 40 year old oil fired boiler, but now that our AC is also ready to be replaced, we are in the market for a new heat pump.

Sounds like any of the two stage/variable speed heat pumps will be great during the shoulder seasons, but we will also need some help in the dead of winter, particularly in the morning after the overnight fire has died. This has led me to look closely at the Mitsubishi line up.

Mitsubishi has the “hyper-heat” technology that allows their heat pumps to deliver heat efficiently at lower temps without the use of electric back up strips. We’re not looking at mini splits though as we would like to use our existing AC duct work for this (if it turns out that the existing ductwork is insufficient, then we may shift our focus to mini splits). There aren’t many options for ducted heat pumps with this technology. Mitsubishi seems to be the only manufacturer to have any available at all. Is this correct and, if so, does anyone understand why?

Anyway it looks like we’re left with either the PUZ-HA30NHA5 which is a 34k BTU heating unit (30k BTU cooling) or a few others such as the MUFZ-KJ18NAHZ which are all around 21k BTU heating.
https://www.ecomfort.com/Mitsubishi-PUZ-HA30NHA5/p80538.html
https://www.ecomfort.com/Mitsubishi-MUZ-FH18NA2/p65203.html
I suspect we’ll need something in between these sizes but I can’t find such a unit from any maker with the hyper heat or equivalent tech.

Does it sound like we’re on the right track here? Should I look more closely at something like the Carrier Infinity line?
https://www.carrier.com/residential/en/us/products/heat-pumps/25vna0/
I’m just scared of the electric resistance backup during the cold winter mornings, and also during defrosting cycles when outdoor temps are below freezing. BTW do those Mitsubishi units even use elec resistance for defrosting??

 

[Brian26]

Just about every mini split company makes a ducted version that connects to duct work. Mini splits have a much better modulation than the carrier unit that looks like its just a 2 speed listed at 40-100% capacity. Electric resistance backup is a thing of the past. The cold weather ratings on mini splits have advanced where many can provide 100 percent heat at subzero temps.

 

[peakbagger]

Fujtisu also makes mini split units set up for ductwork.

One of the reasons minisplits are so efficient are they cut out the ductwork which usually is source of infiltration and unwanted heat transfer. Many ducts are run outside the conditioned space so any leaks means heating or cooling being sent outside the conditioned space.

 

[Highbeam]

Of course the major reason for ducted minisplits is that the inside wall mount units are so dang ugly. I've never met a woman who liked having a big honking hotel like indoor unit hanging on the wall blowing at your face!

Why have the split manufacturers not adopted the same tech? Money. They really have improved, modern split units don't bow out until much lower temperatures than they used to.

I'm also irritated that I can't buy a heat pump boiler for heating water. I'm not talking domestic water but for radiant heat applications. The tech is available in other countries but not here (at any reasonable level)... yet.

 

[begreen]

I’ve been going through some of the older threads on heat pumps and have learned quite a bit- still unsure of some things though...

In Southeastern PA, we heat our 1400 sqft ranch house primarily with a Hearthstone Clydesdale insert. As a backup we have been nursing a 40 year old oil fired boiler, but now that our AC is also ready to be replaced, we are in the market for a new heat pump.

Sounds like any of the two stage/variable speed heat pumps will be great during the shoulder seasons, but we will also need some help in the dead of winter, particularly in the morning after the overnight fire has died. This has led me to look closely at the Mitsubishi line up.

Mitsubishi has the “hyper-heat” technology that allows their heat pumps to deliver heat efficiently at lower temps without the use of electric back up strips. We’re not looking at mini splits though as we would like to use our existing AC duct work for this (if it turns out that the existing ductwork is insufficient, then we may shift our focus to mini splits). There aren’t many options for ducted heat pumps with this technology. Mitsubishi seems to be the only manufacturer to have any available at all. Is this correct and, if so, does anyone understand why?

Anyway it looks like we’re left with either the PUZ-HA30NHA5 which is a 34k BTU heating unit (30k BTU cooling) or a few others such as the MUFZ-KJ18NAHZ which are all around 21k BTU heating.
https://www.ecomfort.com/Mitsubishi-PUZ-HA30NHA5/p80538.html
https://www.ecomfort.com/Mitsubishi-MUZ-FH18NA2/p65203.html
I suspect we’ll need something in between these sizes but I can’t find such a unit from any maker with the hyper heat or equivalent tech.

Does it sound like we’re on the right track here? Should I look more closely at something like the Carrier Infinity line?
https://www.carrier.com/residential/en/us/products/heat-pumps/25vna0/
I’m just scared of the electric resistance backup during the cold winter mornings, and also during defrosting cycles when outdoor temps are below freezing. BTW do those Mitsubishi units even use elec resistance for defrosting??

Several American manufacturers also sell variable speed compressors and variable speed air handlers, Carrier and Trane for example. Problem is that AC ducting and venting can be poorly designed and located for optimal heating sometimes.

 

[wolfonahill]

Fujtisu also makes mini split units set up for ductwork.

One of the reasons minisplits are so efficient are they cut out the ductwork which usually is source of infiltration and unwanted heat transfer. Many ducts are run outside the conditioned space so any leaks means heating or cooling being sent outside the conditioned space.

I found this model but it does not have what they call the "XLHT" technology. I'm also unsure if it will connect to our traditional duct work.

ARU24RGLX : Medium Static Pressure Duct - AIRSTAGE SINGLE-ROOM MINI-SPLIT SYSTEMS - Residential - FUJITSU GENERAL United States & Canada

ARU24RGLX : Medium Static Pressure Duct - AIRSTAGE SINGLE-ROOM MINI-SPLIT SYSTEMS - Residential - FUJITSU GENERAL United States & Canada

www.fujitsugeneral.com

Luckily our duct work runs to each room through the finished basement, so we're good there.


So Mitsubishi calls it "hyper heat". Fujitsu calls it "XLHT". Daikin I'm not even sure has it.
All of the minisplit manufacturers use inverter technology which I guess just means they have a variable speed compressor...

Several American manufacturers also sell variable speed compressors and variable speed air handlers, Carrier and Trane for example.

Would those with variable speed compressors and variable speed air handlers be similar (in low temp efficiency) to the non-hyper heat Mitsubishis/non-XLHT Fujitsus?

 

[begreen]

They show some good numbers, but it depends on the size of the system. The Carrier Infinity 20 has a very impressive 13 HSPF.

 

[maple1]

I found this model but it does not have what they call the "XLHT" technology. I'm also unsure if it will connect to our traditional duct work.

ARU24RGLX : Medium Static Pressure Duct - AIRSTAGE SINGLE-ROOM MINI-SPLIT SYSTEMS - Residential - FUJITSU GENERAL United States & Canada

ARU24RGLX : Medium Static Pressure Duct - AIRSTAGE SINGLE-ROOM MINI-SPLIT SYSTEMS - Residential - FUJITSU GENERAL United States & Canada

www.fujitsugeneral.com

Luckily our duct work runs to each room through the finished basement, so we're good there.


So Mitsubishi calls it "hyper heat". Fujitsu calls it "XLHT". Daikin I'm not even sure has it.
All of the minisplit manufacturers use inverter technology which I guess just means they have a variable speed compressor...

Would those with variable speed compressors and variable speed air handlers be similar (in low temp efficiency) to the non-hyper heat Mitsubishis/non-XLHT Fujitsus?

Yes, Daikin has 'it'. Just not sure they attached a fancy catch name/phrase to their high efficiency units.

We put 2 of their splits in, last November. Very satisfied so far. One of the install guys said he had one of their ducted units in his house & it did all his heating & cooling.

 

[Highbeam]

There are two extremely cool things that minisplits do that split systems don't. One is very high efficiency for both heating and cooling. The other, and I think the "it" you are talking about is the ability to make nearly all of their rated output at very low temperatures. That "it" is a performance spec that some companies have chosen to name.

That low temperature output ability is far more important to many than the incremental efficiency advantage above modern traditional splits at normal ambient temperatures.

 

[Brian26]

I have an electrical monitor hooked up to mine and its staggering how little power it uses. Here is a chart of its usage. It pretty much never runs at full capacity which draws around 1kwh. Notice how it starts at full capacity briefly and then ramps down quickly. Around 1321 you can even see a door open or something and it briefly ramps up.

When these units run at lowr capacities the cop is huge. At 47 degrees at its lowest output drawing 150-175 watts my unit has a cop of 6.36! I live on the CT shoreline so my unit doesnt have great cold weather capacity but its mild here.

 

[wolfonahill]

Thanks for all the help! I've got some sales people coming out this week and I'm feeling a little more comfortable with all of the info I've gathered so far...

Brian26: What is the make of your heat pump? I’ll need something larger but those numbers are indeed impressive. I was also curious about the app you’re using, so I checked out neep.org and WOW that website is really helpful!
It has a list of heat pumps from every major manufacturer and you can filter for ducting config., heating capacity at 5F, etc. Once I narrow it down I can easily compare specs across different units (the disclaimer notes, though, that the numbers coming from different manufacturers may not be apples to apples)
http://ashp.neep.org/#!/

Hyper heat and XLHT are described as technologies separate from inverter technology, but it’s really been tough to find an explanation of exactly what the technologies are. I found this regarding Mitsu Hyper Heat:
"The Hyper-Heating INVERTER outdoor unit uses flash technology which re-collects heat energy that is normally wasted in the flash process at the outdoor coil. This process helps the H2i systems overcome issues commonly associated with conventional heat pumps such as decreases in low-side pressure, refrigerant mass flow rate and operational capacity. The patent pending flash process cools the compressor allowing higher speeds at a lower outdoor temperature without overheating. This also allows increase in mass flow rate in the system providing phenomenal heating performance at low temperatures."

 

[Brian26]

Thanks for all the help! I've got some sales people coming out this week and I'm feeling a little more comfortable with all of the info I've gathered so far...

Brian26: What is the make of your heat pump? I’ll need something larger but those numbers are indeed impressive. I was also curious about the app you’re using, so I checked out neep.org and WOW that website is really helpful!
It has a list of heat pumps from every major manufacturer and you can filter for ducting config., heating capacity at 5F, etc. Once I narrow it down I can easily compare specs across different units (the disclaimer notes, though, that the numbers coming from different manufacturers may not be apples to apples)
http://ashp.neep.org/#!/

Hyper heat and XLHT are described as technologies separate from inverter technology, but it’s really been tough to find an explanation of exactly what the technologies are. I found this regarding Mitsu Hyper Heat:
"The Hyper-Heating INVERTER outdoor unit uses flash technology which re-collects heat energy that is normally wasted in the flash process at the outdoor coil. This process helps the H2i systems overcome issues commonly associated with conventional heat pumps such as decreases in low-side pressure, refrigerant mass flow rate and operational capacity. The patent pending flash process cools the compressor allowing higher speeds at a lower outdoor temperature without overheating. This also allows increase in mass flow rate in the system providing phenomenal heating performance at low temperatures."

Its a cheap $800 Midea I installed myself.

All cold climate mini splits are using vapor injection scroll compressors that Mitsubishi's calls hyperheat. I found this pretty good explanation below.

A really MAJOR difference with cold climate mini-split capacity and efficiency is the use of vapor injection scroll compressors where the vapor injection (not just the compressor speed) is optimized for greater capacity & efficiency within the targeted temperature bands. This is WAY more than mere modulation of compressor speed.

 

[begreen]

Once I narrow it down I can easily compare specs across different units (the disclaimer notes, though, that the numbers coming from different manufacturers may not be apples to apples)
http://ashp.neep.org/#!/

That is a great source of info. My heat pump dealer had mentioned how efficient the Carrier Infinity 20 is. Looks like the -5º specs back it up. This interests me because we have a ducted central hvac system.

 

[wolfonahill]

I wish the Carrier Infinity 20 came in 2.5 ton. Looks like only round numbers, so 2 or 3 ton for me.

 

[maple1]

Have you had any heat loss calcs done? Three tons doesn't sound too oversized for a Central unit.

 

[wolfonahill]

Have you had any heat loss calcs done? Three tons doesn't sound too oversized for a Central unit.

I was hoping to get an accurate heat loss calc done by one of the salesmen coming out, but so far they've just been looking at the square footage of the house and the existing duct work. They're doing it for free though so I can't really complain. Two more companies are yet to come out and if they don't do a good one, maybe I'll see about spending some money on it.

About a year ago when I was looking into this I found a site on the net and did one myself. My poorly taken notes say "inside 70 degrees, 2659 BTU needed". Not sure what outside temp is in that scenario...

 

[maple1]

I was hoping to get an accurate heat loss calc done by one of the salesmen coming out, but so far they've just been looking at the square footage of the house and the existing duct work. They're doing it for free though so I can't really complain. Two more companies are yet to come out and if they don't do a good one, maybe I'll see about spending some money on it.

About a year ago when I was looking into this I found a site on the net and did one myself. My poorly taken notes say "inside 70 degrees, 2659 BTU needed". Not sure what outside temp is in that scenario...

Not sure about those numbers - seem very wonky.

From my past fuel/energy use I have estimated I need an average of around 35,000 btu/hr over the winter. 2700 sq.ft. two story 20 year old construction on an open hilltop in this climate.

 

[Brian26]

You can get extremely accurate heat loss numbers with an electricty monitor on your furnace/boiler. You track how long it runs each hour and you can get your exact btu/hr heat loss.

I discovered my 90k btu oil furnace is like 4 times oversized. My heat loss is around 20 -25k btus/hr around 0 degrees. When its above 32 I easily heat my entire house with 1 12k mini split.

 

[peakbagger]

Be very careful on sizing boilers or heat pumps to account for thermal mass when heating up a structure. If excess capacity is not factored in, if the house gets cooled down unexpectedly or on purpose using a setback thermometer the heating system will not be able to make up for the heating required to bring up the thermal mass back from the lower temp to the higher temp. Most recommendations for mini splits are set the thermostat and forget it so that the thermal mass is always at room temp. It can take 12 plus hours to bring my house back up to temp in cold weather if I am gone on business trip and have the thermostats set low.

 

[wolfonahill]

Well I've had quite a few companies come out to the house and give their opinions, along with some quotes. Only one of them did a really thorough loss/gain calc, which came out to:

Loss: 139,239
Gain: 34,194

This company specializes in both Carrier and Mitsubishi systems. They have given me a quote for the Carrier Infinity 5-stage system (25VNA837A003 + FE4ANF0300), and I am waiting to receive a quote for the Mitsubishi hyper-heat system (PUZ-HA30NHA5 + PVA-A30AA7 ) which I expect to be at least $1k more.

I've been looking closely at the efficiencies of these units, trying to make a meaningful comparison. The hyper-heat unit is the most efficient and maintains full heating capacity down to 5 degrees, still providing heat at -15 degrees (without use of elec resistance).
The Carrier is almost equally efficient down to around 22 degrees, but beyond there it just won't have the heating capacity to heat our home without elec resistance (22 degrees is my best guess, could be higher or lower)

I did a calculation and I wanted to run it by you guys just to make sure I'm not misunderstanding/missing anything too major... I'm just trying to get a rough idea of how these numbers will translate into real money, by comparing the value in efficiency against the upfront costs of installation.

COP for each system above 22 degrees is close enough so we'll call it a wash

Below 22 degrees, we will assume electric strips coming on for Carrier Infinity 5-stage, COP = 1
Below 22 degrees Mitsubishi COP = 2

Between the hours of 2am and 10am (when wood burning insert will need help), # of hours that were 22 degrees or below in:
2016: 136 hrs
2017: 232 hrs
2018: 156 hrs
average of: 177 hrs/yr

10 kilowatts = 34,121.42 BTU/hr (about what's needed to maintain heated house)

Carrier: 10 kw (COP of 1) * 177 hrs = 1,770 kw
Mitsubishi: 5 kw (COP of 2) * 177 hrs = 885 kw

current elec price = $0.06832 per kWh

Carrier: 1,770 * 0.06832 = $120.93
Mitsubishi: 885 * 0.06832 = $60.46

$60.47 difference yearly

ROI break even point: $1,000/$60.47 = 16.5... So to justify paying $1k more for the Mitsubishi, the system would have to last 16.5 years

Other factors in the decision:
Elec price is currently very low, can't expect it to stay that way
I'd be more comfortable reducing my wood habit with the Mitsubishi, if I ever wanted or needed to
I get the feeling the Mitsubishi system will be more reliable, although if we ever did need a part for service, it would take longer to get it fixed

Still waiting on Mitsubishi quote for final price comparison...

 

[sloeffle]

ROI break even point: $1,000/$60.47 = 16.5... So to justify paying $1k more for the Mitsubishi, the system would have to last 16.5 years

Personally, I'd get the Carrier and not look back. I don't think you'll get your money back on the Mitsubishi unit, especially if the break even point isn't until 16.5 years from now at your current electric rate. Even if you electric rates go up, and the ROI is ten years I think you'll still be money ahead. I'd say you'll have replaced the unit by then too.

The 1k you saved could also be put into a S&P 500 tracking stock that has earned roughly 9.8% in return over the last 90 years, and you'd roughly have $4,440 after 16 years too.

 

[orlkc]

I assume the heat loss calculation land ended up as 39k btu/hr (not 139k btu/hr)?

With the prices that close, if they really end up that way, I'd choose based on other items -- which contractor you think will do a better installation job or be more available for future servicing, or whether having the 22 degree cutover will cause you to pay undue attention to minimize runtime in colder weather.

 

[begreen]

wolfonahill I'm a bit confused by these calculations. Our 2006 heat pump has a cutover temp to resistance heat at 25º. The Carrier Infinity series puts out a lot more heat than our unit at low temps. I looked at their 3 ton unit and it is rated to output 35,400 btus at 47º and 33,496 btus at 5º.

Carrier Infinity 25VNA 3 Ton 20 SEER Heat Pump AC Condensing Unit | Carrier HVAC

The Carrier Infinity 25VNA Heat Pump with Greenspeed™ Intelligence provides up to 13 HSPF heating efficiency and up to 20.5 SEER cooling efficiency.

www.carrierenterprise.com

Carrier specs here:

ASHP

ashp.neep.org

The Mitsubishi Hyper Heat is excellent, but it does not look like it's a world better than a like matched Carrier unit.
Mitsub specs here:

ASHP

ashp.neep.org

 

[wolfonahill]

The Carrier unit I was quoted is the Infinity 18VS (25VNA8) and I couldn't find it on the ASHP site. The Carrier systems that they have specs for all use the Infinity 20 Greenspeed (25VNA0). The numbers there, however, are looking inaccurate anyway.
For instance: heating at 17 degrees outdoor temp, Max BTU is 30,600... but then at 5 degrees, max BTU jumps up to 33,496 while COP also gets better?

So I was trying like hell to find official Carrier specs and I eventually gave up and went with Bryant specs because they were easier to find. Everything I have read about Carrier and Bryant says that they are exactly the same inside, but with a different name and different aesthetics outside.

Carrier Infinity 25VNA8 = Bryant Evolution 288BNV
From page 13 here, might have to turn your head sideways: https://www.utcccs-cdn.com/hvac/docs/1009/Public/00/PDS288BNV-08.pdf
Heating capacity at 47F is 34,200 BTU, at 17F is 23,000 BTU... This is the info I used to estimate resistance heat cut-over at 22F (all of these numbers are based on maintaining 70F indoor temp, we could maybe do 68F)

The Infinity 20 Greenspeed (25VNA0) is significantly better though, and I hadn't realized this so I'm glad you brought it up, begreen...

Carrier Infinity 20 Greenspeed (25VNA0) = Bryant 280A Evolution Extreme
From page 15, sorry for your neck: https://www.behler-young.com/UserFiles/Resource/280ANV036000.pdf
Heating capacity at 47F is 33,400 BTU, at 17F is 31,600 BTU... note COP at 47F is 4.4! and according to graph on page 11, it still puts out 24,000 BTU at 5F

I double checked the Mitsubishi specs and they match what's on the ASHP site.

http://meus1.mylinkdrive.com/files/PVA-A30AA7___PUZ-HA30NHA5_Product_Data_Sheet-en.pdf

I actually think the Carrier Greenspeed will be more efficient overall for us though.. Mitsubishi COP at 47F is 3.62 vs Carrier Greenspeed 4.4

I am going to email the HVAC guy right now and ask for another quote...

 

[Highbeam]

Remember that with the Mitsubishi there are no duct losses and you have to look at a stupid wall unit. The traditional split is a ducted unit with real filters and uses normal looking vents, duct losses can be significant if they are outside of the envelope.