Mini-Split AC/Heat Systems - Questions

[oliver2-44 9,699]

I installed a Mini-Split AC/Heat system in the garage of the house I remodeled for my son.  They use the garage for there dog training business.  I knew it didn't have heat strips, but with the record cold weather in Texas I earned a few things.  it will operate down to about 20F efficiently, then just dies and goes into alarm.  We were able to use a portable electric heater to keep the garage warm enough for the dogs.  It's nice that it operates this low, as my home heat pump doesn't operate that low.  These Mini-Split systems are quite popular for remodels or even some new installations around here.

 

So I know there are some AC/Heating guys on here.  So my questions are, in colder areas are Mini-Split systems used? 

If they are, how do users add emergency heat to those systems?

 

[rmaynard 15,428]

My next door neighbor has them. I will ask as soon as I see him. 

[DennisThornton 4,769]

Used all the way up here in Plattsburgh NY but borderline in brutal cold.  Electric backup is probably cheapest if your panel can handle it or perhaps a Rinnai or other good brand with propane or liquid fuel.  I sold a lot of Rinnais and Toyotomis and only a few minis.  I gather some minis have electric resistance backup built in but our brand didn't. 

[1995 520H+96+97 937]

This is what I have, don't use in winter, yet.

 

[squonk 41,038]

Heat pump has to be rated low enough to work. We installed a Mitsubishi in a school that was rated to 20F  With a  wind deflector on the outdoor unit it will work down to 0f . Does yours have one? 

Edited February 21, 2021 by squonk

[roadapples 6,983]

I plan on having  2 installed. Was under  the  impression you could get them  with propane  backup...

[DennisThornton 4,769]

1 hour ago, roadapples said:

I plan on having  2 installed. Was under  the  impression you could get them  with propane  backup...

I've been out of the loop since Covid and minis weren't my focus but I've never heard of built in propane backup for minis.  Would be a MAJOR addition where electric resistance is simple with electric already being there, though you'll need more amps than normal.  I didn't push minis as the sole source of heat with no other backup since we get below Zero F up here, though I've been told that some with Fujitsu's did manage.

[WHX?? 48,795]

3 hours ago, roadapples said:

I plan on having  2 installed. Was under  the  impression you could get them  with propane  backup...

Ney Ney  ... no such thing 'Apples, that I am aware of I anyway and pretty much keep up on these appliances since it's how I put horses in the barn. No way to put electric strip heating on them. PTACs yes and some of those may have an option for propane or even hot water back up. 

 

I was never a big fan of them, ductless,  truth be told. They are all junk just somes better junk than others. Most of them you have to be a Philadelphia lawyer or have alot of experience with that brand, yup they are all different, bolstered by lots of technical training. You put in in yerself or your contractor got it at home cheapo all bets are off. Refrigerant charge has to be spot on for proper operation and it's real tricky for minis.

 They work good when they do but a bear to fix & $$ when they go kaput.  

Early days they all came from Japan. Nowadays China ...go figure or Korea.

The thing with minis is they have to be rated and usually oversized for any kind of serious heating work.  

Any heat pump the capacity drops as the outdoor temps drop. Some will lock right out as you are experiencing Jim. 

Some can run down to 0 deg and even below. It all depends on the manufactures rating. Mitzus are the industry  leader for running in low temps.

 

So to answer your question Ollie no there is no way to put a emergency heat on them and no we would never use them for our cold up here except for what we call three seasons rooms or the the "swing times", fall & spring milder temps. for spot heating. Electric heat is a real no no up here ...wayyyyy too expensive.  Down on your turf in most instances work fine last a long time. 'Cept when mother nature throws us a ringer. 

 

Sounds to me like you guys down ther caught the engineers syndrome. They way underate the outdoor design temperature.  Up here the lowest outdoor we are supposed to  design by temp is -15, it goes by zones in the US .... when I design/build  a system I use -30 in my calcs ..see pic below.  You guys should be designing at 0 deg..... does it happen in TX or FL? Guess we know the answer to that. 

 

 

 

BTW  @1995 520H+96+97... don't ever believe  the manufactures statements... they like to blow their own horn and are ALWAYS full of BS. Funny how those guys ain't  around at at midnight on Christmas when their engineering don't work. 

 

Edited February 22, 2021 by WHX24

[WHX?? 48,795]

4 hours ago, squonk said:

Heat pump has to be rated low enough to work. We installed a Mitsubishi in a school that was rated to 20F  With a  wind deflector on the outdoor unit it will work down to 0f . Does yours have one? 

Way below 0 is now is standard out of the box Mike for Mitz's. Bottom line now is how much do wanna spend?  I recently did a server room for a school where the college educated boys wanted horse crap. This guy in the trenches I know put in an economizer that cooled the space for free as well as distributed electronics heat when needed by other spaces. 

[squonk 41,038]

9 hours ago, WHX24 said:

Way below 0 is now is standard out of the box Mike for Mitz's. Bottom line now is how much do wanna spend?  I recently did a server room for a school where the college educated boys wanted horse crap. This guy in the trenches I know put in an economizer that cooled the space for free as well as distributed electronics heat when needed by other spaces. 

School called us. " Here put this in" we found out later it was only rated for 20.. You get what you pay for. Most server rooms I've dealt with were old mop closets with a rack and the mops still there. Add some old desks,a copier and a stack or 2 of paper. You couldn't even get in there to clean the air filter.

Edited February 22, 2021 by squonk

[squonk 41,038]

15 hours ago, WHX24 said:

Way below 0 is now is standard out of the box Mike for Mitz's. Bottom line now is how much do wanna spend?  I recently did a server room for a school where the college educated boys wanted horse crap. This guy in the trenches I know put in an economizer that cooled the space for free as well as distributed electronics heat when needed by other spaces. 

Funny you should mention the economizer Jim.

 

When I worked at the hospital, we had the Bermuda Triangle of server rooms. About 12' X15' in a rickety old stick  building that used to be a nursing student dormitory. Straight out of the 50's. When I started there were 2 racks in there and a little 2 ton EMI split. They were adding racks so they added a 5 ton Carrier. Evaps on the wall and the ceiling was maybe a foot above the racks. Thru the years they kept adding racks and battery back ups, copiers and had to add another 5 tons with another Carrier. It was a mess. The wire trays were above the racks and the evaps blew directly on the wire racks diffusing the air in all different directions. The cool air struggled to get to the openings in the servers and the hot air out of them had to detour around junk piled behind the servers to get back to the evap.

 

Room had no other form of ventilation. You would walk into the room and feel hot spots, cool spots, no spots. It was like crossing the Equator.

The rest of the bldg was cooled by an ancient Trane Chiller through fan coils. When that thing quit the whole bldg heated up and the heat would work it's way into the server room and we would have to put in portables ac's in the room to keep it online until the chiller was fixed.

 

3 count them 3 times  during Capital project meetings I suggested that we add either a rooftop or outdoor unit capable of brining in cool air during spring fall and winter and with more AC capacity during the summer. The I.T. guys thought it was a great idea and so did the Trane engineers, but My idiot Supervisor and Facilities Director were worried about humidity so they wouldn't even let us look into it further.

 

Fortunately server technology started changing shortly before I left and they started upgrading and were actually removing racks and lowering the heat load. Plus they finally started to clean the junk out of the room. 

Edited February 22, 2021 by squonk

[WHX?? 48,795]

One important thing to know about them is the blower wheels which are long small diameter skinny affairs have a tendency to get dirty real fast. Just the nature of those types of wheels.  Even when those filters under the cover are spotless. Poor airflow across the evap. can cause lockouts. They are a royal pain to get out and clean. 

[oliver2-44 9,699]

On 2/22/2021 at 9:32 AM, WHX24 said:

One important thing to know about them is the blower wheels which are long small diameter skinny affairs have a tendency to get dirty real fast. Just the nature of those types of wheels.  Even when those filters under the cover are spotless. Poor airflow across the evap. can cause lockouts. They are a royal pain to get out and clean. 

I appreciate the maintenance heads up on that.

[DennisThornton 4,769]

On 2/22/2021 at 10:32 AM, WHX24 said:

One important thing to know about them is the blower wheels which are long small diameter skinny affairs have a tendency to get dirty real fast. Just the nature of those types of wheels.  Even when those filters under the cover are spotless. Poor airflow across the evap. can cause lockouts. They are a royal pain to get out and clean. 

I only sold a few in my short career with Mini-Splits but I never heard that complaint.  What brand or brands might I ask?

[pfrederi 17,674]

Have had Fujitsu unit for about 9 years now.  3 inside units.  The will generate heat down into the single digits. Cold damp  weather it spends time defrosting. I will sometimes use the electric baseboard to help out in severe cold also have a coal stove downstairs which helps out but not so much at the ends of the house upstairs.  We keep the house at 75 or so day time in the winter.... Only issue we have had is the condensate tray in one unit developed a crack and would drip water.  Took forever to get the part but it was replaced no charge (Inside unit had to be pulled and then recharged after)..