Mini Split?

tobrien02382

Hi All, My family and I own and occupy a three-family in New England (built in 1900). We currently have steam heat, cast iron radiators with two oil burners. We are considering installing a Mitsubishi ductless system with "hyper heat". The current proposal is 5 heads (1 on the third floor 2 on each first and second floor). Ideally, we would like to heat and cool all three units with these being our primary heat source in the winter and our a/cs in the summer. Thoughts?

pecmsg

Steam heat is very comfortable during cold windy winters. Heat pumps will do the job but during defrost cycled operate in Cooling to thaw the outdoor coil. Gets a little uncomfortable for those 5 - 10 minuets. If there sizing for heating load they WILL be oversized for your cooling needs, this can create additional issues the major one is a growth on the internal components.
If your doing 1 or 2 outdoor units with multiple indoor other issues can arise. Manly over heating / cooling on heads that should be off.

Size them for the cooling needs, use the heat mode in the spring and fall to take the chill off and the steam for those cold windy nights.

tobrien02382

Thank you so much for the input! The proposal is to install two Mitsubishi M# MXZ-5C42NAHZ2 45,000 BTUs which I should have included in my initial description.

pecmsg

tobrien02382 said:

Thank you so much for the input! The proposal is to install two Mitsubishi M# MXZ-5C42NAHZ2 45,000 BTUs which I should have included in my initial description.

Without knowing the Manual "J" Heat Load / Loss for the building I cant discuss sizing.

Jamie Hall

They may work well (if they are properly sized for the cooling load, and properly installed) in the summer and shoulder seasons. They will not be satisfactory in the winter time -- so keep the steam in good operating condition.

JUGHNE

Is that 45,000 X two?
Sounds like a lot of cooling for the NE, IMO.

pecmsg

JUGHNE said:

Is that 45,000 X two?
Sounds like a lot of cooling for the NE, IMO.

Probably sized for the new Keep Windows Open mandate!

tobrien02382

Hi All! Thank you for your input. This has been a learning experience. Just for some further background. The house is 3500 square feet divided almost equally into 3 apartments.

pecmsg

tobrien02382 said:

Hi All! Thank you for your input. This has been a learning experience. Just for some further background. The house is 3500 square feet divided almost equally into 3 apartments.

Thats still guessing

If you can read a ruler you can do your own calculation here
https://www.loadcalc.net/

ethicalpaul

JUGHNE said:

Is that 45,000 X two?
Sounds like a lot of cooling for the NE, IMO.

That was the sizing for heating and cooling loads I believe. If Tricia were going to take the reasonable advice above to size them for cooling and for use in the shoulder seasons, she would have to have it resized and re-estimated by her contractor I think.

STEVEusaPA

Along with all the other advice, keep in mind, if you get a huge snowstorm/high drifts/ice storm, and your outdoor unit gets covered/ices up, probably no one is going to be able to come out and fix it, so you'll need another heat source.

ethicalpaul

Indeed, it might require...a shovel!

JUGHNE

In defense of MiniSplits, I must confess that I put a truckload of them in a 40 bed nursing home for mainly cooling. The heat pump portion did pretty well in the winter time.
Inside design heating temp for nursing home is 80 degrees.

These are high end Mini's that thankfully shut down at I think 5 degrees.
Each room has huge electric convection heater for real heat.
At about 30 degrees the HP output drops off and those heaters will take over.

I did find one HP running even though it was completely buried under a snow drift.
It was inside this little ice igloo and still putting out some heat.

IMO, with any heat pump, if you can avoid operation that requires constant defrost cycles, their life is extended quite a bit.

So sized with cooling only in mind, you get better humidity control when you need it.
And you will get enough heating to carry you thru the "shoulder" seasons and then use the steam system when you want some "real" heat. FWIW

TAG

Is this a single compressor w/ multi heads. Branch box? You need a really good heat load done on the building -- and each space.

I know MA has some great programs -- there is a member here who does the Mitsubshi systems.

Sized properly they can work -- it's all math (fuel cost). I will say -- steam/hot water is nice heat especially in an older house with some leaks.

SuperTech

Like @pecmsg stated, biological fuzzy growth buildup is a real problem with every mini split system that I see. Regardless of what brand and how clean of an environment it is in it seems like after a year the indoor units start getting this stuff accumulating in them. Deep cleaning with a bib kit or disassembling and manually cleaning them is the only way to keep them sanitary.  These systems are also a real pain to service when something electrical fails. I've never seen any techs stock parts for these units. 

They are great when they are sized and installed properly, and are efficient.  They don't dehumidify well and have the service related issues I stated above. I'd stick with the boiler for heating and consider other options for cooling.  

Mook531

Just a heads up, in case you didn’t know. One of the issues with converting to wall mounted units is dead spots, like bathrooms, large closets, etc. Even though it’s called ductless you can install ducted units to take care of larger areas. This is from a house I just finished that converted from hot water. House sounds very similar to yours.

pecmsg

Very nice install

tobrien02382

Thank you all. We are considering two options one is to have one system with 6 heads. That system is rated to 30 degrees. There is a $ 1250 rebate for that. The other is to run two systems with 3 heads a piece. That one is rated down to 5 degrees with a rebate of $ 875 (x 2). The difference coming out to $ 4250 when all is said and done. The plan would be to install on 12" stands. What I'm hearing everyone say is that no matter what we will still be using the old boilers. We were hoping to not have to use them at all. Regardless, we still need SOMETHING to help even the temps throughout the house. I appreciate all of the advise!

pecmsg

I do not like Multiple head units because most installing contractors cant flair worth a damn! 1 bad flair and the entire unit goes down. 2 indoor with 1 outdoor reduces the chance of loosing a large system. How good are you going to feel about the rebates when the system is down and the house is cold?

If you want to go all heat pump its your choice, I prefer using it for the shoulder seasons only!

ryan242

Definitely keep the steam heat maintained and usable when the temps drop, I live in central Pennsylvania and I have a boiler system as well as mini splits, I didn’t install either, they were already here prior to me moving in, i don’t really like the mini splits at all to be honest, they work good when the weather is mild.. 40’s-50’s and when it’s hot for days on end, 85+ Seems to be where they actually kind of dehumidify, but anything between 75-85 forget it, they suck at dehumidification even in “dry” mode. Also like mentioned above, they get moldy inside really fast even if you keep the filters cleaned every few weeks. I wish you the best of luck with yours though. Would I install them if I didn’t already have them prior to buying my house? Nope!

GW

I'm always fascinated with how hvac companies sell this stuff. If the home is brand new then sure why not. if it's a condo- sure why not. But an older typical home, why yank the old system out? Very aggressive move. You may not be thrilled with electric heat in the bathrooms, and cold spots as the winter gets super cold. But we all have out definition of comfort and value and perceived/actual 'green' energy.

GW

@Mook531 very nice, I dig the radius throat off of the ahu and the rad pair of pants. Clearly you're bending your own metal. Any issues with white lines yet? Is that a Kumo up top? I normally tuck them inside the bottom. Is that Fortress line hide? Golly that stuff makes me weez, i can't snap it for beans. Very nice job

Mook531

GW said:

@Mook531 very nice, I dig the radius throat off of the ahu and the rad pair of pants. Clearly you're bending your own metal. Any issues with white lines yet? Is that a Kumo up top? I normally tuck them inside the bottom. Is that Fortress line hide? Golly that stuff makes me weez, i can't snap it for beans. Very nice job

Had a few issue with the white lines, but I think it may have been from bubbles used during leak testing running down. We have to put float switches on every head here, so not much more room i there for the limo, also. Yeah, it’s fortress, I hate the stuff, but that’s what they buy us. Thanks for the compliments.

JakeCK

Wait, you can duct mini splits?

ratio

@JakeCK, yeah, there's ducted concealed heads (5th pic) & air handlers (4th pic) both. There's also a standing cabinet similar to the old enclosed radiators. Depends on the mfgr.

I prefer anything to the wall tumors, myself.

Campyman

pecmsg said:

I do not like Multiple head units because most installing contractors cant flair worth a damn! 1 bad flair and the entire unit goes down. 2 indoor with 1 outdoor reduces the chance of loosing a large system. How good are you going to feel about the rebates when the system is down and the house is cold?

If you want to go all heat pump its your choice, I prefer using it for the shoulder seasons only!

Most contractors don't do it right. Here's a video I posted about five years back that goes over how to flare and properly torque the fitting so it will last: https://www.youtube.com/watch?v=cag7DUHIo0M

TAG

When doing the multi head units that all tie back to the compressor it's very important to review the operational manual and take note of the BTU outputs. Mitsubishi has charts where you can see the exact heads and compressors and what they will output. You can not just look at the single head specifications and think the multi head work the same way. The units that use the branch boxes work more like the singles -- but, again .... it so important to do the load needed and match both the rooms and the full load of the house.

Have two 3 head systems in two different houses -- both are 3x 12k on a 30k compressor. The older one is from 2015.

I own a house in a community with a lot of big victorians. There is a local company that has made a nice business out of installing multi head system in these houses ..... many have nine heads and branch boxes. Expensive -- but they work. Everybody did them for AC ... but find they use them for heat more than expected. No one that I know of took out the hot water heat and they use that in the cold weather. The nice thing about having a mini is you can boost a given room above what the hot water is doing ... that what most people have been doing.

As far as the heads -- being ugly. In some situations they are -- with some thought and placement they go away more than one would think. I have done the wall w/ eye mostly -- but have also used the ceiling with a multi. I have one floor that's a single on it's own compressor. I was thinking of using the air handler as in the above picture .... I went with two systems mostly for control

KC_Jones

Have you done all you can to balance the steam system properly? I saw you had another post talking about TRV's and not working properly. Before a TRV will work the system has to be as balanced as possible (main venting, rad venting), then go to a TRV when the typical solutions aren't getting it where you want it. TRV's are definitely not a solution for other problems.

I agree with all the above, heat pump would be fine down to a certain point, but then you will want the steam system.

You should also look up videos about cleaning the heads on the mini splits to make sure you are ok with doing it, or paying someone to do it, as regular as necessary.

GW

@Campyman nice job with the vid. We're a little nutty about flares too. If i may, try and make the insulation a little long, then when you cut, cut it right up against the insulation slice. No exposed copper that way. I know i know, it's certainly exposed inside the unit, but just a little pro touch. Also, you gotta get a digital torque wrench! I hope you Seattlites are fairing well after the summer of Love, looked scary on TV

Campyman

Thanks. I actually got a digital one now. I've installed at least 500 ductless units and no call backs for leaks. Funny how things last when you follow the manufactures recommendations, torque settings.

kenjohnson

I'm a technically-oriented and homeowner with experience with several different mini splits in three different installations. I am not a contractor. Just FYI.

I've had a Fujitsu RLS2H (equivalent to Mitsubishi hyper-heat) installed in two different houses - it was a single head and a single outdoor unit. I've also had a Mitsubishi hyper-heat unit with two indoor heads and one outdoor unit installed in a condo. These units will provide heat down to about -15 degrees F and cool in the summer as well.

The Fujitsu is used in both houses as a backup heat source and primary shoulder season heat source, augmenting an oil-fired boiler and wood stove. It works great. Frankly, there is just one head in a 1700 and a 1200 square foot house so the heat didn't circulate great to the entire house (not surprising), but it can take the burden of the heating load off the oil boiler during much of the year if I wanted to run it that way (especially if I was gone for long periods, which I was). Luckily, in my current house my oil boiler is zoned, so I can run the oil heat in the front of the house and the mini split in the back during all but the coldest months, if I wanted to. I don't run it in January or February because my basement will get pretty cold without the oil boiler running during the coldest months of the year. These houses are in a climate where nights close to or below zero are common.

The Mitsubishi heats a condo and is the primary heating source. The backup is central Trane heat pump that uses too much electric backup heat for my liking. It still works, so I didn't take it out, but I never run it anymore. The Mitsus work great - no complaints.

One downside of the hyper-heat style units is that they are not as efficient at warmer temperatures. If you get a unit that only works to 5 degrees F, it will be far more efficient at higher temperatures. Personally, if I had a house with a working fossil-fuel system, I'd probably keep it and just get mini-splits that work to 5 degrees F or 17 degrees F and reap the better efficiency for the 90% of the heating season that it is warmer than this. FYI - the efficiency improvement for the non-hyper heat units is probably 50% improvement at shoulder season temperatures. And the non hyper-heat units are less expensive as well.

As for sizing, if you dialed back your requirements for whole house heat to 70 degrees at winter design temperature, it will probably get a little smaller, a little less expensive, and be more efficient at summer cooling as well. If your fossil fuel system failed for some reason in the winter, the mini-splits could still keep your home from catastrophic below freezing temperatures.

Just a homeowner's two cents.