18k or 24k mini split

[Tracs]

I know this has been discussed to death.

I currently have a 18k BTU mini split in my 24x30x10 garage. The 18btu cools it in the summer (90 degrees) and does make heat down to 15 degrees.

Here in Manitoba in the winters it gets to -30F from time to time.

I'm looking at Napoleon NH25 series model that will make heat to -22F.

I got a quote, I asked for 18k but it shows a 24k and the price on that is too good to pass up.

Do I go up to a 24k or stick with 18k BTU?

If I stick with 18k I could reuse wiring 20 amp breaker and probably the lineset. The 24k using larger lines and a 25 amp breaker

 

[jack stand]

Is this new unit in addition to the older, or a complete replacement?
From your breaker and lineset question it seems like you're replacing.

 

[chinboys]

The biggest problem with an oversized or undersized unit is it runs too long to cool or heat the area of use or it doesn't run long enough thus the humidity isn't brought down but the area is cold and damp.
Did you run or did someone run the heat loss or heat gain (heat transfer load) on the garage or is the current 18K BTU doing its job?
Are you looking for a better SEER rating by going to a newer unit?
Have you thought about adding ceiling fans to help circulate the cooler or warmer air?
Most heat pumps work at their most efficiently above 40F. They can work to -10F but may have heating coils to add supplemental heat which isn't efficient in the heat pump transfer cycle or for your wallet.
Perhaps, time to add a secondary oil, propane, or natural gas dedicated heater instead.

 

[American Locomotive]

FYI: Looking up the datasheet for that unit, by 17*F it's down to 19,800 btu heating. While it says "heats down to -22", you're probably only going to be getting ~10,000 BTU of heat out of it, if that.

 

[Tracs]

Thanks for the responses.

This replacement is primarily aimed at Winter heating.

This would be a complete replacement of the 18k btu unit. The current unit worked just fine cooling the garage in the 90 degree heat we get for 2 months in the summer. So 18k btu would be sufficient.

I have a 6kW boiler for the in floor radiant heat that I use in the winter. It heats the garage respectively, but I feel I could use a bit of warm circulating air.

The idea of a new mini split unit is to replace the current one that is leaking slowly from the outdoor condenser/compressor. So the current one needs replaced either way.

Since I am replacing the mini split, I want one that will make heat to the lowest possible temperature that the current technology allows, which for these units is -22F.

I am not concerned that the heat btu output drops substantially as the outdoor ambient temp drops. As long as it makes a breeze of warm air at -22F I would be happy.

With the inverter design I would think that at 24k btu it would throttle itself up and down to meet cooling demands. So I am not concerned about over sizing.

The main question is now at -22F is there a difference in heat output between the 18k and 24k? The sales brochure says the 18k model makes 17k btu heating and 18k btu cooling. The 24k model does 24k btu heating and 24k btu cooling. Logically thinking that at -22F there is only so much "heat" that can be extracted from the ambient outdoor. So would the 24k be able to "make more heat" than the 18k at -22f?

 

[toyotadriver]

Yes the 24k should move more heat than the 18k at the same outside temp.

 

[Phuckin' Jim]

Napoleon?
Where in Manitoba did you find that?

 

[Tracs]

Napoleon?
Where in Manitoba did you find that?

My Uncle can get it for me. He isn't a HVAC tech but does duct work and has a Mopia #.

 

[Phuckin' Jim]

Cool.
Those look like the Midea units.
If you go to Senville.ca you'll find spec. sheets on their units, I bet they're strangely similar to the Napoleon units.
I checked the specs for the Carrier Performance units, and they're identical to the Senville specs.
Also check neep.org.
Lots of information on there.

I couldn't find anyone around here to sell me one locally, so I ordered one from Senville.

 

[Tracs]

Cool.
Those look like the Midea units.
If you go to Senville.ca you'll find spec. sheets on their units, I bet they're strangely similar to the Napoleon units.
I checked the specs for the Carrier Performance units, and they're identical to the Senville specs.
Also check neep.org.
Lots of information on there.

I couldn't find anyone around here to sell me one locally, so I ordered one from Senville.

I was going to order a Senville, but then found out about the Napoleons and got a price that was a couple hundred less than the Senville. But the Senville comes with a line set. So it is a toss up on price between those 2 brands. The Napoleon offers a slightly better warranty with 10 years on Parts, Compressor, System. The Senville says 10 years Compressor, 5 Years Parts.

 

[American Locomotive]

Pretty sure that Napoleon is exactly the same as a Senville Aura.

 

[C2F]

If you buy a mini split with an inverter you can oversized the unit. It slows down the speed of the compressor. A 24k btu unit probably lowers its output down to 6,000 BTU’s for cooling mode.

Upsize for mini splits on inverters. I’m a tech with 15 years experience.

 

[Tracs]

If you buy a mini split with an inverter you can oversized the unit. It slows down the speed of the compressor. A 24k btu unit probably lowers its output down to 6,000 BTU’s for cooling mode.

Upsize for mini splits on inverters. I’m a tech with 15 years experience.

The Napoleon sales brochure doesn't specifically call it an "Inverter" but does use the term "high efficiency direct current compressor motor ".

Is that the same thing?

 

[Phuckin' Jim]

I would say so.

 

[Phuckin' Jim]

ASHP

ashp.neep.org

This look like the one you are looking at?

 

[Tracs]

ASHP

ashp.neep.org

This look like the one you are looking at?

That is the one.

 

[Phuckin' Jim]

Definitely inverter then.

 

[Tracs]

As a follow up the 18k BTU Napoleon NH25 will be here tomorrow or the next day.

A 24K would have required a new breaker, wire, and line set.

 

[dcg9381]

FYI: Looking up the datasheet for that unit, by 17*F it's down to 19,800 btu heating. While it says "heats down to -22", you're probably only going to be getting ~10,000 BTU of heat out of it, if that.

Definitely consider the performance curve at temperature. I have Daikin units, below 30F they really fall off in terms of heating. At 20F they are really bad and have to alternate defrost cycles just to clear the ice off the condenser and will not come close to heating our building. I'm sure that there are units (Mitsu Hyper heat) that are better, but I basically moved to 20k-30k ventless wall mounted propane heaters when it gets cold... But we have propane available.

 

[Tracs]

Definitely consider the performance curve at temperature. I have Daikin units, below 30F they really fall off in terms of heating. At 20F they are really bad and have to alternate defrost cycles just to clear the ice off the condenser and will not come close to heating our building. I'm sure that there are units (Mitsu Hyper heat) that are better, but I basically moved to 20k-30k ventless wall mounted propane heaters when it gets cold... But we have propane available.

I don't need to rely on this unit to heat the garage. I have radiant hydronic floor heating. It would just be nice to have a wisp of warm air now and then in the coldest of winter.

This new unit will be replacing a damaged 17 seer 18k BTU.

 

[PoorOwner]

I have 18k on similar footage, drywall without insulation, it works great. 90F isn't that warm.

Only time it could not "work" is 104F outside and I pulled a car in, the garage didn't cool down until night time.

 

[Doozer75]

The biggest problem with an oversized or undersized unit is it runs too long to cool or heat the area of use or it doesn't run long enough thus the humidity isn't brought down but the area is cold and damp.
......

Why do people keep saying this.
It is not a binary control unit.
It is variable speed.
A mini split.
It basically runs all the time.

-Doozer

 

[yeldogt]

Why do people keep saying this.
It is not a binary control unit.
It is variable speed.
A mini split.
It basically runs all the time.

-Doozer

You still don't want to oversize .... the minimal output is an important number

 

[Doozer75]

There is no minimal output number.
It CAN still shut off, even though it is a variable speed unit.
I intentionally oversized my Mistubishi Mini-Split.
My 900 sq ft insulated shop has a 31,000 btu unit.
Seems oversize to me.
I get flawless QUIET cooling in the summer
and very warm heat pump operation in the winter.
Why are you sticking to giving advice that does
not make sense ?

--Doozer

 

[shade]

I have 48k cooling in 900 Sq ft.
I sure don't mind the 'oversizing' all these 'professionals' like to state.
Keeps the garage cool and pull down times bringing in cars from the 110 degree heat is great.

 

[FL Guy]

If you buy a mini split with an inverter you can oversized the unit. It slows down the speed of the compressor. A 24k btu unit probably lowers its output down to 6,000 BTU’s for cooling mode.

Upsize for mini splits on inverters. I’m a tech with 15 years experience.

Does the output slow down when the unit gets closer to the set temperature?
I’m guessing if there’s a 4°+ difference in temperature, then the “inverter” will blow on high speed?

 

[FL Guy]

There is no minimal output number.
It CAN still shut off, even though it is a variable speed unit.
I intentionally oversized my Mistubishi Mini-Split.
My 900 sq ft insulated shop has a 31,000 btu unit.
Seems oversize to me.
I get flawless QUIET cooling in the summer
and very warm heat pump operation in the winter.
Why are you sticking to giving advice that does
not make sense ?

--Doozer

What kind of insulation do you have in your building?
I’m at 900 sf with spray foam

 

[FL Guy]

I have 48k cooling in 900 Sq ft.
I sure don't mind the 'oversizing' all these 'professionals' like to state.
Keeps the garage cool and pull down times bringing in cars from the 110 degree heat is great.

Do you have a problem with “short cycling” as I’ve read time and time again? I’ve seen jt can be an issue with a mini split that’s bigger than what’s needed?

 

[shade]

Do you have a problem with “short cycling” as I’ve read time and time again? I’ve seen jt can be an issue with a mini split that’s bigger than what’s needed?

I personally dont

 

[PoorUB]

I'm looking at Napoleon NH25 series model that will make heat to -22F.

I have been looking at specs on that unit and can not find any mention of BTU output at -22F.
Like another post mentioned, you might not get much heat output at -22F.

I used to sell mini splits. Many of then advertise heating to minus "whatever -F" but few of them will produce any usable heat at the claimed number. The heat output drops of dramatically at some point, maybe 10-20 degrees above their claim. A few will actually produce some heat at the claimed numbers.

The main question is now at -22F is there a difference in heat output between the 18k and 24k? The sales brochure says the 18k model makes 17k btu heating and 18k btu cooling. The 24k model does 24k btu heating and 24k btu cooling. Logically thinking that at -22F there is only so much "heat" that can be extracted from the ambient outdoor. So would the 24k be able to "make more heat" than the 18k at -22f?

Show me the printed specifications! The 24K should produce more BTU that the 18K, but without looking at factory specs nobody can say for sure.

I have seen the same model series and a smaller BTU rating produce more heat than it's larger brother in severe cold. Without seeing the factory specs it is impossible to say.

 

[fitter30]

Here is a submittal on a hyper heat condenser. They post btu ratings at 47° f and 17° if you want other btu ratings the factory tech line can give you that info.

https://images.salsify.com/image/upload/s--7o1WjErr--/fl_attachment/bntfhwtihukqrucuegse.pdf

 

[chrispyny]

Not an hvac tech. But i did install a fuji and pioneer unit from scratch myself. Fuji was 24kbtu with an 18k head and 7k head. Pioneer is 18kbtu with 2 9kbtu heads.

I suggest oversizing. These ramp down as they are inverter mini splits. They slow down to nothing.

Question to all here. Does no one install Pioneers anymore? I love mine. If either splits failed me, i’d be on highseer same day ordering another pioneer system.

 

[ching0n]

When I was looking, it was not uncommon to have the heating capacity being the same amongst similarly sized units while cooling being different. I'd check that first. I don't think it's uncommon to oversize your cooling because heating is typically insufficient for colder regions. I worried about heating capacity (HPSF) first before cooling.

I crossed shopped specs from different vendors w/similar SEER figuring most come from the same shop in Asia (based on remotes and manuals)

 

[Highbeam]

Lot of old timers in this thread providing advice based on yesterday's technology. The whole, "they don't make heat when it's cold" group is wrong if you use modern equipment rated/proven/designed to make heat when it's cold. Sure, the units make less heat in the cold but that's still plenty if you properly sized the system for your needs.

My mrcool minisplit provides the data charts to show output at -22F. My unit is a 24k model and puts out 8.11 thousand btu of real heat at -22F with a COP of 1.18 compared to 2.0 at 17 degrees F which means it is more expensive heat but still heat and much cheaper than straight electric. Even at 32 degrees F the COP is only 2.17. This is a 2022 unit and not a "cold weather special" or hgyperheat unit.

I sized the 24k to be adequate for heating at my coldest design temperature of 5 degrees F. That means is usually oversized for heating and really oversized for cooling. No big deal. You could either oversize one unit like I did or buy two minisplits and only fire up the second one when needed. Same thing.

 

[dcg9381]

Lot of old timers in this thread providing advice based on yesterday's technology. The whole, "they don't make heat when it's cold" group is wrong if you use modern equipment rated/proven/designed to make heat when it's cold. Sure, the units make less heat in the cold but that's still plenty if you properly sized the system for your needs.

My mrcool minisplit provides the data charts to show output at -22F. My unit is a 24k model and puts out 8.11 thousand btu of real heat at -22F with a COP of 1.18 compared to 2.0 at 17 degrees F which means it is more expensive heat but still heat and much cheaper than straight electric. Even at 32 degrees F the COP is only 2.17. This is a 2022 unit and not a "cold weather special" or hgyperheat unit.

I totally agree with you. The point I like to make is that not all mini-spits have the same heating efficiency.
And your unit cools 24K BTU. I didn't look up the curve, but how much does it heat at 0F? It's never been that cold here, but mine would not do very well. (Daikin)

So now we've got to size units for the cooling of our building and then the heating of our building at <whatever traditional low> temps are in the area. That probably makes sense in the midwest, but when I did my install I didn't even think about it.

I learned the hard way. My 2 x 24k units cool 2400 sqft fine in Texas when it's 100 degrees out, but when we hit 25 degrees F, they don't have a chance to keep up, building temps drop into the 50s... Maybe colder, that's as cold as I let it get.

Course, we get about 12 days per year at 32 degrees on average. It's been 7 years since we hit 23 degrees.

Should I have installed 4 units instead to keep up with the <10 days we get below 30 F every year? I think I would still make the same choice.. I just found that I had to add portable propane heaters.

 

[ching0n]

I totally agree with you. The point I like to make is that not all mini-spits have the same heating efficiency.
And your unit cools 24K BTU. I didn't look up the curve, but how much does it heat at 0F? It's never been that cold here, but mine would not do very well. (Daikin)

So now we've got to size units for the cooling of our building and then the heating of our building at <whatever traditional low> temps are in the area. That probably makes sense in the midwest, but when I did my install I didn't even think about it.

I learned the hard way. My 2 x 24k units cool 2400 sqft fine in Texas when it's 100 degrees out, but when we hit 25 degrees F, they don't have a chance to keep up, building temps drop into the 50s... Maybe colder, that's as cold as I let it get.

Course, we get about 12 days per year at 32 degrees on average. It's been 7 years since we hit 23 degrees.

Should I have installed 4 units instead to keep up with the <10 days we get below 30 F every year? I think I would still make the same choice.. I just found that I had to add portable propane heaters.

might be your SEER. Plenty 24k units out there w/17SEER. I wouldn't bother w/anything below 21 in the future.

 

[dcg9381]

might be your SEER. Plenty 24k units out there w/17SEER. I wouldn't bother w/anything below 21 in the future.

Yep, they are 17 SEER units. Pretty decent price jump at 21 SEER, but makes sense that those units would heat better.

 

[Highbeam]

And your unit cools 24K BTU. I didn't look up the curve, but how much does it heat at 0F? It's never been that cold here, but mine would not do very well. (Daikin)

I gave the heat output at -22F which is crazy cold out for my location. They don't have a data point for 0F but at 5 degrees F the output is 15.42k btu which is dang good and enough to heat my home alone. It also has about the same COP or efficiency from 5 degrees to 32 degrees F and then starts climbing as temperatures increase.

When sizing heating equipment you have to choose if you want to stay fully warm in ALL possible conditions or if you're willing to suffer or perhaps even utilize a backup heat source during the extremes. I picked an all time low temperature and will be warm which means that for most times of the year I oversized. That seems to be working fine with no drawbacks from short cycling.

The heating load drives the size of the unit in my location. Some areas will use the cooling demand as the design criteria. That's location specific but the equipment has known performance numbers for all situations.

 

[Tracs]

OP here. I installed the NH25 Napoleon 18k btu last fall and used it through the winter for supplemental heat.

It worked great and made heat even in -30 temperature. Sure it wasn't a steady stream of hot air, but it was a cycle of warm air. I am completely satisfied with the unit.

 

[ching0n]

Yep, they are 17 SEER units. Pretty decent price jump at 21 SEER, but makes sense that those units would heat better.

you'd be surprised. I dunno what your budget is but I've kind of put all import inverter units in the same basket (except mitsu & fujitsu). Customer/tech support will likely be better for "mr. cool" and they have precharged lines but I'm fairly certain they all come from the same x nubmer of places. Even the Daikin units look the same and are priced as if no longer Japanese (which I suspect they're not).

I picked up my "ductless aire" 24k 21 seer for 1450$ from home depot and my "rovsun" 12k 20.5seer delivered from amazon for like 550$. The 24k worked great in a few cold days I had in the teens.