Mini-split 12,000BTU vs 18,000BTU?

[borped]

Hi everyone, I'm having a heck of a time figuring out what ductless mini-split system to get. I've talked to 6 installers and half say 12,000, the other half say 18,000 and they all seem very sure of themselves.
Here's a plan of my house: http://imgur.com/mxgOynC it's a one floor bungalow with finished basement in Montreal, Quebec. We have pretty good temperature extremes here, in the coldest days in the winter are about -20C/-4F and in the summer it can be very humid with highs of 30C/86F and a humidex of 40C/104F.

Our attic is insulated to R50, the current heating system is electric baseboards, the windows are all new, and I don't know what the exterior wall insulation is, house is 1978 brick/aluminum siding. The unit would be installed on the left side wall between the living room and dining area pointing straight down the hallway.

Some installers insist that if we get 12,000 in the summer the AC will be running at max CFM all day to keep up and will be lacking in the winter at generating heat. They say an 18,000 wouldn't need to run so high in the summer, would be quieter, and could get colder if we need it. And that in the winter the 12,000 wouldn't be enough whereas with the 18,000 we probably wouldn't even need to use the baseboards at all if we kept the bedroom doors open. On the flipside some installers say the 12,000 is perfect and that 18,000 would be overpowered for our house, that in the summer the 18,000 wouldn't be able to run 24/7 and would cycle on/off too much. They said it's not an issue in the winter so much, more heat is rarely a bad thing.

So which is it?

 

[jebatty]

I have no experience with your situation at all. Yet, if it was me, I think I would do the following.

Have a couple of your installers on each side of the issue prepare a detailed heating/cooling load analysis for your home which they provide to you in writing, research that against info on the same available from the web, and then decide which likely is more accurate.

Or, on the heating side, determine the monthly kWh consumed by baseboard this season and historically for heat, correlate with temperatures each month, convert kWh to btus per month (kWh x 3412 = btus), divide by 30 (days in the month), divide by 24 (hours in a day) and see what the btuh works out to be. What is closer: 18,000 or 12,000 btuh? The same would work for cooling.

For heating, I assume you will retain your baseboard. At some point as outside temperature drops, depending on the specs of the mini-split, you may be heating mostly with resistance electric, same as baseboard, and you always can supplement with baseboard as needed during the cold seasons, so the heating load may not be as critical as the cooling load. Cooling, unless you have existing AC, you don't have an option to supplement during the high heat/humidity periods. Research whether better to over-rate or under rate cooling btus for your system.

 

[woodgeek]

You are not going to size a HP to be ideal for heating and cooling at the same time, unless you live very close to Atlanta Georgia. Size it for heating. This can be rough for a single-stage system....my sized for heating HP has a hard time dehumidifying in the summer, until I fiddled with it. With a variable speed mini....total non-issue IMO.
Easy decision: Get the bigger one. When its below -10°C, you will be glad you did.

 

[peirhead]

Welcome to the forums Borped...I grew up in Montreal so I know your concerns....firstly the single heatpump upstairs will do nothing for your downstairs, so it will be all baseboard for the lower level. My current house is very similar design and I have a pellet stove downstairs that heats the house almost completely as the heat rises (and cool falls) through the nice open stairway (mine is very open) A lot of the heat goes up so we keep the downstairs at around 23C to keep upstairs around 21C...If I was to switch to a heat pump i would put in a 12K BTU downstairs and a 9K upstairs, but if I only wanted 1 pump, it would be downstairs! Conversely if your primary concern is AC for the summer, upstairs would be the place to put it. By the way My Pellet stove is 32K BTU rated and at 70% efficiency (reality here) so I get about 24K BTU delivered by the stove. Our temps here are...avg winter temp is around -5C

Use JEBattys calculations in the above post to work out your actual BTU needs and then I'd design for heat and take the cooling as a bonus!

Hope this helps

 

[semipro]

I believe most mini-splits are variable output systems so that oversizing them is not a problem like it is for other fixed-capacity systems. One problem with sizing for cooling used to be that oversized systems did not sufficiently dehumidify because of short cycling. Oversizing for heating is not an issue in general.
Go with the bigger one.

 

[valuman]

I believe most mini-splits are variable output systems so that oversizing them is not a problem like it is for other fixed-capacity systems. One problem with sizing for cooling used to be that oversized systems did not sufficiently dehumidify because of short cycling. Oversizing for heating is not an issue in general.
Good with the bigger one.

This ^
The FH-1800 Series Mitsubishi that we installed last summer has a dehumidify setting that will run constantly. That does provide some minimal cooling as well but it bypasses the thermostat so you can run it until you've gotten the humidity down to what you want. Also, the auto settings for both Heating and Cooling modulate as conditions dictate. That way the unit only works as hard as it needs to, minimizing both sound levels and electricity consumption. I'm very impressed with the engineering of this machine and am really glad we installed it here, only 3.5 hours south of Montreal.

 

[borped]

Thanks, my main concern is to not be over powered for AC and end up short cycling with an 18,000 BTU unit.

 

[woodgeek]

Thanks, my main concern is to not be over powered for AC and end up short cycling with an 18,000 BTU unit.

Variable speed compressor units, as in minis, do not short cycle.

 

[borped]

Variable speed compressor units, as in minis, do not short cycle.

Really?? This is so confusing, I had at least 3 or 4 installers tell me not install too big of a unit because in the summer it won't run all the time and will turn on/turn off which consumes more power and does a worse job at removing humidity from the air than getting a smaller unit that would run 24/7.

The model I'm looking at is the Gree Hansol 12,000, you can see the stats here: (broken link removed to https://www.master.ca/documents/regroupements/1Gree_Hansol_eng.pdf)

So with this unit there would be no danger of of getting the 18,000 BTU unit and having any issues other than perhaps wasting $600 on more BTU's than I need? I want to equally use it for AC in our humid summers and as our main source of heat the rest of the year with baseboards to fill in the gaps.

One other question for whomever wants to answer, this unit comes with a 10 year warranty on parts, compressor and labour which seems quite nice. Another product I was looking at a Comfortmaker unit that is 30 SEER and works as low as -30C is around the same price with 10 year warranty but labour not included. Typically when something breaks, is the labour expensive?

And I'll look into this myself but if anyone has a quick answer please feel free to share your answer, would a 30 SEER machine cost half as much to operate winter and summer than a 15 SEER machine? I'm just trying to figure out at where the point of diminishing returns is on paying more for higher SEER. Thanks!

 

[woodgeek]

Gree is a cheap Chinese brand without a lot of fans in the US. I saw a bunch in Hong Kong, they seems to be working ok there. I would get one if the price was right.

The top lines in the spec sheet give a range of BTUs in heating and cooling. That is the throttle range and it looks like 20% to 100%. IOW, it can throttle down 80% during cooling to avoid short cycling. The 18000 unit can drop down to 4600 cooling BTUs, similar to a modest window unit. It will not be oversized or struggle to dehumidify (at least not because it is too large).

Your installers appear to be giving you advice about old style, single speed units rather than minis. Perhaps they are new to minis.

SEER is for cooling, HSPF is for heating. Higher is better, and your operating costs are indeed inversely proportional to the #. So a SEER 30 unit will cost half as much in cooling as a SEER 15, but that is prob not a big concern for you. You could compare the HSPFs, but in practice the bigger BUT unit will always be cheaper to operate b/c it will deliver more cheap BTUs and reduce your baseboard BTUs, whose HSPF by the way is just 3.414.

 

[semipro]

If you want to test your installers' knowledge ask them to show you their "Manual J" calculations.
A bad response would be a blank stare of befuddlement.
A good response would be the argument that load calculation aren't needed since mini-splits are variable output.
A great response would be that they show you the calculations and tell you they picked the unit based on those calculations and the variable range of minisplit output.

Based on my (and many others') experience with Chinese-made refrigeration; the 1st gen. Geospring water heater, I'd avoid the Gree. There are some really good mini-splits out there, foreign and domestic, and they've earned a deservedly good reputation. I think the cheaper units are riding on their coat tails.

BTW: I'm not sure how cold it gets in Toronto but some mini-splits feature efficient heat pump operation at very low temps. Some also feature backup resistive elements for extremely low temps.

There are several others here that know mini-splits pretty well and use them. If we've made you uncertain about your choice of contractor or manufacturer then maybe you could start over with a request for recommendations. Just a thought.

 

[borped]

So why avoid Gree if it has a 10 year warranty? If something goes wrong I don't pay for it right? Or is there more to it?

I know Fujitsu and Mitsubishi get high marks but I really don't want to spend that much just for a name brand. What would be some of the best value brands? Not expensive but not junk?

 

[jebatty]

Ways to judge a warranty are to judge the expected longevity of the company (will it still be around when I need the warranty service?), the warranty performance record (does it honor its warranty promptly and competently?), the warranty frequency record (how often are warranty claims made, i.e. what is the underlying quality of the product?), the warranty interpretation record (is it a real stickler on the consumer's compliance with the details of the warranty, failing which it will deny coverage?).

 

[borped]

Ways to judge a warranty are to judge the expected longevity of the company (will it still be around when I need the warranty service?), the warranty performance record (does it honor its warranty promptly and competently?), the warranty frequency record (how often are warranty claims made, i.e. what is the underlying quality of the product?), the warranty interpretation record (is it a real stickler on the consumer's compliance with the details of the warranty, failing which it will deny coverage?).

Doesn't Gree make half the air conditioners on the market for all types of brands? I'm assuming this means they'll be around in 10 years. Regarding warranty performance record, frequency record, and warranty interpretation record, how can I get this information on Gree or any other company for that matter?

Is there a recommended value brand for people who don't want to spend $4,000 on a Fujitsu or Mitsubishi?

 

[peakbagger]

If you want a AC unit non name brands may work but if you need cold weather operation. I would stick with the name brands. In order to get cold weather performance, they are pushing the limits of the equipment and I expect that's where second tier brands may not be up to the task. I really haven't heard of any other brand that has made any penetration into Maine which is definitely a tough place for minisplits.

The alternative is go on Ebay and buy a Mitsubishi from a dealer for a lot less, install the majority of the unit and hire a tech to purge and charge the lines and take your chances with no warranty. They do guarantee them if they dead when delivered but shipping it back is definitely a hassle. From what I have been told by several techs, the units rarely fail due to warranty issues, its usually poor installs or external abuse, like damage to outdoor unit or the tubing. If there is a rare warranty claim they just swap in a replacement unit. When you look at the markup local dealers charge, you can by a spare outdoor unit and still be ahead.

 

[woodgeek]

I think Gree is a 'cheap' choice. No one can tell you if it is 'value'. When I got my (non-mini) HP, I went big and cheap (Goodman), and have no regrets. As for cold weather operation and efficiency, I think 90% of HP output vs temp is the thermodynamics of the refrigerant....when the vapor pressure drops too low with outdoor temp, the unit output drops proportionally. The other good bit is variable speed (mini is better than single speed) and smart defrost controls.

The gree uses the same Puron refrigerant as the other brands. Part of the 'improvement' of HPs in the last 10 years is the new refrigerant....which just has higher vapor pressure at low temps.

So long as the OP is cognizant that the output will be chit much below 20°F, where he spends a lot of hours, and then he will still be paying for backup, then I think the hypothetical marginal superiority of the Japanese brands is a small gain (in savings) for a big gain in up front.

The OP is not expecting to heat his conventional house in Toronto all winter with a mini. Just to take a big bite out of winter heating bill (in non-Arctic weather) and get a little summer dehum and AC. And not break the bank doing it.

If you are satisfied by the Gree warranty, get it, along with the biggest unit you can. The extra 50% output 18kBTU versus 12kBTU will increase your savings nearly 50% (by getting you 50% more BTUs during cold weather) and doesn't cost 50% more up front.

Also, I know in the US the big box stores sell Gree...can you get an extended warranty (i.e. with labor/shipping/etc) from the local retailer?

 

[browneyesvictim]

All spot on advise above!

Cant speak for Gree, but I have been running a Mitsubishi Mini-split for a few years now and absolutely love it! Zero regret. Love the inverter technology, and definitely how quiet it is! I'm running a City-Multi PUMY S series unit which is actually a more commercial unit
(Nominal 12.5 - 15.5kW cooling / 14.0 - 18kW heating). There is a reason they have a great reputation and is not just brand a name. Secondly you should consider it money in the bank for resale value. I am unable to open your link, but in any case, I wouldn't skimp on the size of the outdoor unit, and take advantage of multiple smaller indoor units for zone heating/cooling.

 

[borped]

So essentially all anyone recommends is Fujitsu and Mitsubishi, no value brands?

 

[semipro]

Seems like there's a lot of unit comparison discussion at HVAC-talk
E.g., http://hvac-talk.com/vbb/showthread.php?1621671-Mini-Split-Decision-Help&p=20563671#post20563671

 

[begreen]

So essentially all anyone recommends is Fujitsu and Mitsubishi, no value brands?

Daikin is a good brand too. Locally I have seen some Sanyo and Panasonic units that seemed pretty good, but not sure how they spec out.

 

[georgepds]

So essentially all anyone recommends is Fujitsu and Mitsubishi, no value brands?

When I looked they had the best winter summer hspf/seer ratings

I have a Fujitsu rls2h 12 kbtu for my downstairs. My next unit will be a Fujitsu rls3h 12kbtu for the upstairs. I live in a leaky house in ma/nh border

Take a hard look at the performance numbers

 

[maple1]

Fuji, Mitsu & Daikin are on my radar.

Local situation & contractors might play a part too, guy closest to me does Daikin & has happy customers.

Also have a buddy who had an LG put in last winter. He's happy too, so far.

 

[begreen]

When I looked they had the best winter summer hspf/seer ratings

I have a Fujitsu rls2h 12 kbtu for my downstairs. My next unit will be a Fujitsu rls3h 12kbtu for the upstairs. I live in a leaky house in ma/nh border

Take a hard look at the performance numbers

One note of caution on these units. A friend had the larger 18K Fujitsus installed locally. In the first winter there was a power surge and it burned out the control units. They were without heat for a week as they waited for the parts. If your power is rural and somewhat erratic invest in surge protection. It's worth the cost.

 

[georgepds]

One note of caution on these units. A friend had the larger 18K Fujitsus installed locally. In the first winter there was a power surge and it burned out the control units. They were without heat for a week as they waited for the parts. If your power is rural and somewhat erratic invest in surge protection. It's worth the cost.

Ahh.. I'm in a wood stove forum because the power used to go out regularly on my barrier island. The heat pump is backed up by two propane wall units (one that requires power, one that does not) in case the heat goes out while I'm not there. During the cold season, most of my heat comes from the Woodstock progress hybrid.. with the heat pump filling in if I sleep late

Before I had the very quiet heat pump, the powered propane heater would light up, sounding like a C5A taking off, and waking the dead and me three blocks over. That used to be my cue to put more wood in the stove


That said.. what do you recommend for surge protection

 

[begreen]

Your electrician should be able to fix you up with one for the HP circuit. Intermatic is one major brand.