poor performance from Samsung mini-split

[cowanrg]

the title pretty much says it all, I'm not happy with my Samsung mini-split. I've had it for around 6 months now and in the summer it took the edge off in the garage, but never really got 'cold' (got down to the high 70's maybe), and now that winter is here, it's nearly pointless as a heater.

My workshop is an ~800 square feet attached garage and it seems to be relatively well insulated. The other day when it was around 18 degrees out in the morning, the garage only dipped down to around 45 degrees. Not bad. The weather was the same the next day and I needed to work on some stuff so when I woke up I turned on the mini-split. The best I could get was 52 degrees by around 1pm (and that was measured right next to the unit, not on the other side of the garage). It took that whole time to slowly creep up. By that time, the outside temp was about 40, so it was really only getting ~12 degrees above outside temp, which seems pretty pathetic for a 24k BTU unit.

The unit is a Samsung AR24KSWSJWKN. I wasn't able to find the exact model on their site (probably been replaced with something else), but the label says it's a split system and heat pump. The cooling capacity is 21K BTU and the heating is 27K BTU. It was pretty much the top of the line at the time with WiFi and such. The air coming out of it is like 'room temperature', but never really warm or hot. It just feels like a breeze that's not necessarily cold, but not really warm either. It runs for maybe an hour, and then stops because the lines get frozen, then goes back on, etc. In the time it's not running, I lose a degree or two, then it heats up a few degrees, then I lose most of that, etc.

So I guess my question is, should this be adequate to heat up the garage, or is there something wrong with the unit? I just feel that a little 120V space heater could give me about the same performance. Should I get it checked out, or are these things just not meant to provide much heat?

 

[matt_i]

I think the lines freezing is classic symptom of low charge.

In my opinion you should be getting very cold air out of the evaporator as without going very low temp humidity will not be extracted. This is very bad as it then outputs cold, clammy air.

 

[cowanrg]

I think the lines freezing is classic symptom of low charge.

In my opinion you should be getting very cold air out of the evaporator as without going very low temp humidity will not be extracted. This is very bad as it then outputs cold, clammy air.

The unit outside is blowing some pretty cold air, and there's some condensation on the concrete below the unit. The air blowing from inside isn't cold by any means, it's just not what I would call 'heat'.

So you think it might not have been charged properly? Just doing some more reading, it seems like a 27K BTU heat pump should be able to get my 800 square foot space up to at least 60 degrees, unless it's in single digits outside. But it's like 30-40...

 

[matt_i]

I'm Sorry, my poor response didn't address your question. Skimming without really read the whole thing. Its heating you are having trouble with and not cooling.

I think you'll get 100% of rated heating capacity down to around 50F ambient. Then linear drop to zero F although it will consume 100% of rated input amperage the entire time.

So if its 40F outside then you are getting around 80% of 27k = 21k BTU, at 18F you are getting around 9k BTU. That's not a whole lot of heat input. You'd also have to leave it running 100% which is probably not the greatest for energy consumption because there's not going to be a lot of extra heat to make a big change in the ambient if you are heating it sporadically.

However it does seem there's poor performance. One of the issues is the refrigerant isn't doing what its supposed to if its low charge or wasn't fully evacuated.

 

[Ohmthis]

It definitely has issues, non which can properly be diagnosed over the Internet. Low charge, low air flow, dirty coils, bad linear expansion valve, these are some possible issues. Who installed the unit? There may be leak in the system or it was never charged correctly. When in the 30's you should be feeling very warm air. You may need a tech to check it out.

 

[bazar01]

It's a new install and only 6 months.
You should get it checked by the installer.

I have a 12k btu made in China and it is putting out a lot of heat out the front vent on a 35F outdoor temp.

 

[cowanrg]

Cool, good to know. I didn't expect the internet to troubleshoot this for me, just a sanity check to see if it should be performing better. I was thinking about getting an electric heater to supplement this, but it sounds like it should be plenty. I just want to maybe get up to 60 degrees, that's all. 27K BTU (assuming it's not super cold outside) sounds like it should be plenty.

I had it 'professionally' installed, but he was a bit slow and didn't really seem to know what he was doing with it the whole time. We bought the house and the main AC unit needed to be serviced along with the furnace and we just kinda bundled the mini-split into the deal. So there's a good chance it's not working 100% correctly, I'll contact him and see if he can fix it. Of course, if he's going to charge me, I'll go with someone else that knows them better. But he should be doing this for free since it doesn't seem like it was hooked up properly to begin with.

 

[cowanrg]

UPDATE: Had my AC guy come out and check everything out. He said it's working properly, it's just not designed to bring the whole garage up to temp quickly. For anyone that owns a mini-split for the garage, do you guys just keep it on the whole time and maintain temperature rather than only turn it on when you need to get in the garage? So let's say I have a project that I need to do over the weekend, should I be turning it on Friday night to get up to temp and just keep it on the whole weekend?

 

[Jackfre]

What is the room air temp entering the evaporator? What is the exiting temp? Please be careful when getting the later. I have had guys stick a probe up the air side and tear up the fan. Don't be like them. FYI, I get a 30-40* delta T on my units

 

[cowanrg]

I measured this yesterday, room temp was around 40, and air exiting the wall unit was ~80F.

We're trying to keep it on continuously to see if it can maintain better than coming up from 35 degrees. I checked my energy usage last weekend and having it on for an entire day (from around 7AM until maybe 6PM), it was around 10KWh, which is about a dollar based on our rates. That was starting at 35 degrees and coming up to 60, both days. It would have been more efficient if it was just working intermittently I think.

 

[toyotadriver]

Mini splits don't kick out a lot of heat. They are a poor choice for a place where you want to quickly heat it up. If you are keeping it at a constant temperature they can be really good depending on your climate. I think for your uses you would have been much better served with a gas heater. You would have probably heated it with a 45k btu gas heater which would put about 36k btu into your shop.

We don't know where you live. Big difference in a place that gets to 18 overnight and 50 during the day and a place that gets to 18 overnight and 30 during the day.

What do you consider good level of insulation?

 

[My Old Tools]

Garages and shops can contain large quantities of metal. Metal is a great heat sink. If you let a big shop with say a bandsaw, tablesaw, jointer, several toolboxes full of hand tools get down to 40 degrees, it is going to take a lot of BTUs to raise all that metal back up to 60 degrees, much more so than just air. I know my big cast iron machines seem to just radiate cold in the winter.

 

[cowanrg]

I'm located in Colorado. So it's not exactly Minnesota, but not Arizona either... But it's really dry and it doesn't get really cold very often. Today is an exception, with the high being around 15 degrees.

It's interesting because I researched what to install in the shop for about 6 months and everyone on here recommends a mini-split for year-round comfort unless you live in some place that's REALLY cold.

I left the unit on for about 24 hours now. During the day (when it was around 20 outside), it got the shop up to mid 50's. This morning (having the unit on all night, set to 61 degrees, the lowest it goes), it was around 45 out there. So, it's doing about 20-30 degrees, which is fine on all but the coldest of days.

I will look up in the space above the garage to see how much insulation I have. It might be a good idea to get better insulation in the roof/attic and possibly replace the garage doors with more insulated ones. If I can get an extra 5 degrees out of that, it should be sufficient. It's rarely 10-20 degrees outside (during the day), so I can just wear some layers when it's that cold. Maybe get an electric heater to supplement.

I want to avoid a gas heater because I don't really want to run an extra gas line out there.

 

[toyotadriver]

I suspect you are lacking insulation as problem number 1. What's the R value of the walls? How many garage doors and are they insulated? What kind and how much insulation in the attic?

If you have natural gas but don't want to run a line, you could install an electric 240 volt resistance heater and then use it to supplement the mini split.

 

[cowanrg]

I suspect you are lacking insulation as problem number 1. What's the R value of the walls? How many garage doors and are they insulated? What kind and how much insulation in the attic?

If you have natural gas but don't want to run a line, you could install an electric 240 volt resistance heater and then use it to supplement the mini split.

Unfortunately, I'm not sure on any of these. I didn't build the house, so I'm just not sure. The garage doors are insulated, I just don't know the R value. I haven't looked up in the attic yet, but I can certainly add more insulation. That would probably be my first step.

Yeah, I think adding a 240V heater would be a good way to supplement for the coldest of days. Would it be possible to use the same breaker that the mini-split is on to run the heater? I wouldn't run both of them at once.

 

[Jackfre]

You could try it. I'm assuming a 30 amp breaker for the mshp. Don't push it. You don't want to start cooking boards, etc. you could easily run the elec and the fan only on the mshp.

 

[James-W]

Would it be possible to use the same breaker that the mini-split is on to run the heater? I wouldn't run both of them at once.

Why would you not want to run both the heater and the mini-split at the same time? I would think that would be the most practical thing to do. The mini-split would be the main heat source and the electric heater would supplement when the mini-split couldn't keep up.

 

[toyotadriver]

A 240 volt heater needs to be on it's own breaker. The wire is sized based on the amp draw of the heater.

An electric resistance heater would be the cheapest to install but likely the most expensive to run. However, since you already have a mini split for the garage you'll only need to run it occasionally.

You mentioned that it had a hard time keeping it cool in the summer. That leads me to suspect that you don't have enough insulation in the attic. Maybe none if it's a newer build.

 

[cowanrg]

A 240 volt heater needs to be on it's own breaker. The wire is sized based on the amp draw of the heater.

An electric resistance heater would be the cheapest to install but likely the most expensive to run. However, since you already have a mini split for the garage you'll only need to run it occasionally.

You mentioned that it had a hard time keeping it cool in the summer. That leads me to suspect that you don't have enough insulation in the attic. Maybe none if it's a newer build.

The mini-split just got a brand new 240V breaker, with new wiring. So, I would just tie into that. The wiring should be adequate.

In the summer I was doing the same thing, just turning it on when I needed it. I never really used it to maintain a temperature. When it gets warm again, I'll certainly try that. But you might be right, I might not have enough (or any) insulation in the ceiling. I need to check that out.

 

[toyotadriver]

Don't put the heater on the mini split circuit. It needs to be on its own circuit.

 

[Jackfre]

If you try this on the same circuit make sure you have an amp meter to check the draw. You have sophisticated electronics in the Samsung unit. If there is any feedback or disruption of clean power to the Samsung it will at least fault out and quite likely fry boards.

 

[cowanrg]

UPDATE: I crawled up in the attic. Good news and bad news. Good news (in a way), there's no insulation in the attic. That means I can add some insulation and get much better heating. The bad news is there's a TON of stuff up there from the previous owners. Lots of wood scraps, I think the previous owner was a wood worker. I'm also deathly afraid of heights, which makes this even worse ;-( I'll need to clear out quite a bit before I can start insulating it.

 

[bzinsky]

the title pretty much says it all, I'm not happy with my Samsung mini-split. I've had it for around 6 months now and in the summer it took the edge off in the garage, but never really got 'cold' (got down to the high 70's maybe), and now that winter is here, it's nearly pointless as a heater.

My workshop is an ~800 square feet attached garage and it seems to be relatively well insulated. The other day when it was around 18 degrees out in the morning, the garage only dipped down to around 45 degrees. Not bad. The weather was the same the next day and I needed to work on some stuff so when I woke up I turned on the mini-split. The best I could get was 52 degrees by around 1pm (and that was measured right next to the unit, not on the other side of the garage). It took that whole time to slowly creep up. By that time, the outside temp was about 40, so it was really only getting ~12 degrees above outside temp, which seems pretty pathetic for a 24k BTU unit.

The unit is a Samsung AR24KSWSJWKN. I wasn't able to find the exact model on their site (probably been replaced with something else), but the label says it's a split system and heat pump. The cooling capacity is 21K BTU and the heating is 27K BTU. It was pretty much the top of the line at the time with WiFi and such. The air coming out of it is like 'room temperature', but never really warm or hot. It just feels like a breeze that's not necessarily cold, but not really warm either. It runs for maybe an hour, and then stops because the lines get frozen, then goes back on, etc. In the time it's not running, I lose a degree or two, then it heats up a few degrees, then I lose most of that, etc.

So I guess my question is, should this be adequate to heat up the garage, or is there something wrong with the unit? I just feel that a little 120V space heater could give me about the same performance. Should I get it checked out, or are these things just not meant to provide much heat?

I installed 20 mini splits on my own, only 9k btu's for 600sq ft apartments.

I've had contractors installed various btu rated mini-splits.

For the one's installed on my own, I followed all the little **** suggestions by GJ members. Flaring, vacuuming, nitrogen, everything perfect.
These units perform incredible. They have 0 problems heating and cooling 600sq ft apartments. There is only one 9k/btu unit in each apartment.

Every single one installed by a contractor just seems to stink with performance. I measure the output temperature, everything seems within spec.

I don't know what it is they are doing wrong and I don't know how to check it, but I think most contractors are screwing up some vital step. Possibly the vacuuming, not sure.

I would guess 1 in 10 hvac contractors really know what they are doing with them. The remaining 9 get them to work, and don't get any callbacks on them because there is no measuring device to tell anybody they are putting out 75% of their rated capacity.

 

[bzinsky]

seriously somebody needs to invent something so regular people can check the performance of their AC system.

It's such a huge expense for so many people and nobody has a clue if they are performing as they should. The only time somebody knows is when they basically aren't working at all.

 

[DC73]

Good news (in a way), there's no insulation in the attic.

Yeah, that's not terrible news. At least now you know. Depending on where you are in Colorado, they recommend attic insulation to be between R38 and R60. Here's a link that will help you decide: https://www.energystar.gov/index.cfm?c=home_sealing.hm_improvement_insulation_table

More than R60 is likely to be overkill but putting as much as you can afford up to that level should make a tremendous improvement in the performance of your mini-split. I like mineral wool insulation but, the best bang for the buck is likely to be blown cellulose, especially if you can do it yourself. HD and Lowe's will loan you the blowing machine with the purchase of insulation. Blowing cellulose is a bit messy but it performs better than fiberglass.

DC

 

[DC73]

seriously somebody needs to invent something so regular people can check the performance of their AC system.

It's such a huge expense for so many people and nobody has a clue if they are performing as they should. The only time somebody knows is when they basically aren't working at all.

There's a couple of tricks you can use to check performance. For an AC system, the supply vent nearest the air handler should be putting out air that is 17 to 20 degrees cooler than the air entering the return air duct. You can put thermometers in the ducts or use a laser thermometer. I do this quick check at the start of each cooling season.

Another trick an HVAC tech showed me is to feel the suction line (largest of the two refrigerant lines) just as it enters the condenser (outdoor unit). He said it should feel "beer can cold". If it doesn't feel cold enough that you would want to drink that beer, it's a good sign something is not right with the system. Warning - this trick may not work for the rednecks among us who have no qualms about drinking warm beer.

For heating, furnace specs include "temperature rise". This should be on the nameplate label of the furnace. You can measure the supply temperature at the supply vent nearest the furnace and compare it to the temperature at the return air duct. If there is much deviation from spec, it points to a potential problem. For example, my shop furnace calls for a 30 degree minimum temperature rise. When I last checked it, I was getting 103 degree out of the supply vent and the return air was around 71 degrees so my system was okay.

I like running these tests when I know the system is working properly to give me a base line. Then, if future tests start to deviate, I can keep my eye on the system.

DC

 

[toyotadriver]

UPDATE: I crawled up in the attic. Good news and bad news. Good news (in a way), there's no insulation in the attic. That means I can add some insulation and get much better heating. The bad news is there's a TON of stuff up there from the previous owners. Lots of wood scraps, I think the previous owner was a wood worker. I'm also deathly afraid of heights, which makes this even worse ;-( I'll need to clear out quite a bit before I can start insulating it.

The lack of insulation says a lot about your heating systems lack of performance.

If you do blow in insulation, I recommend cellulose. You can eeasily diy as long as there are two of you.

You should pull off an outlet plate and then look inside the wall to see if you have any insulation in the walls.