High Wall HVAC

[mwbailey]

In the loft of my workshop, we've installed a high wall split system for heating and air. The loft is less than 450 square feet, but does have a peaked ceiling that runs up to maybe 15 feet from less than 7 feet on the "knee walls".


Today was 45-50 degrees outside but we couldn't get above 62 inside. HVAC guy said the unit might be located too high -- he checked for coolant, error codes, and all that.

Any thoughts?

 

[Charles (in GA)]

Ceiling fans?

Did you bother to check the temp at the peak?

You really could use the fans.

Charles

 

[brewchief]

What size unit?
Was a heat loss calc done?

 

[mwbailey]

We have a ceiling fan that the HVAC guy turned on full blast but still had 10 to 15 degree difference between set point and actual temperature! HVAC guy checked the temperature of returning air and output air. He said return was 73 and output was 113, or something like that -- before he turned on ceiling fan. Don't know about after.

The unit is 12K, which should be sufficient for less than 450 square feet give or take peaked ceiling.

No heat loss calculations to my knowledge. The unit was selected and installed by the builder, so I figured they would do what was needed. . . .

One issue that developed is the installers' boss died the week after installation so now there's a new organization coming in behind them!

 

[Charles (in GA)]

I'm assuming this is a fully closed in area, and not open to the shop on one end?

I don't understand why you would have this problem, Does it feel cold? You cannot get it above 62F and the return temp (which is effectively room temp) is 73F ?

This is a mini split system? You are not real clear on that. Is that it, the white box, on the wall at the very top of the pic? I would have wanted it down lower on the wall.

Ceiling fan should have evened out the temp right away. With 113F coming out (and going up) it would have to have been pushing warm air down. Don't run it on high, rather low, or med low will be very effective.

Charles

 

[mwbailey]

Charles, Here are responses:
I'm assuming this is a fully closed in area, and not open to the shop on one end?Yes, that's correct. Ceiling has 6" foam insulation and is supposed to be R-33; exterior walls have 4" foam and are supposed to be R-20; "interior" (red) wall also has fiberglass insulation between 2X4 studs.

I don't understand why you would have this problem, Does it feel cold? Yep, the wife has brought her space heater up to the loft! You cannot get it above 62F and the return temp (which is effectively room temp) is 73F ? Actually, got up to maybe 64 today with almost 70 outside temps and thermostat on 70 or 72. . . .

This is a mini split system? Hmm, don't know about "mini" but it IS a split system rated at 12K Btu. You are not real clear on that. Is that it, the white box, on the wall at the very top of the pic? I would have wanted it down lower on the wall. Yep, that's it near top of picture. 6-inch beam plus "decorations" to hide wiring and piping sort of dictated the higher location. Installers actually suggested the location which was about 6-10" higher than I thought it was going to be.

I left the ceiling fan on low during midday, pointed the vents downward as much as possible, and set the heater fan on high. Didn't seem to help too much. I hate to think that the unit is mounted too high, but that might be it. Funny how it's called a "high wall unit"!?!

 

[zmaxmotorsports]

Ceiling fans?

Did you bother to check the temp at the peak?

You really could use the fans.

Charles

Thats where I would start

 

[zmaxmotorsports]

We have a ceiling fan that the HVAC guy turned on full blast but still had 10 to 15 degree difference between set point and actual temperature! HVAC guy checked the temperature of returning air and output air. He said return was 73 and output was 113, or something like that -- before he turned on ceiling fan. Don't know about after.

The unit is 12K, which should be sufficient for less than 450 square feet give or take peaked ceiling.

No heat loss calculations to my knowledge. The unit was selected and installed by the builder, so I figured they would do what was needed. . . .

One issue that developed is the installers' boss died the week after installation so now there's a new organization coming in behind them!

Where is he getting these temps from?

 

[Charles (in GA)]

As well insulated as that space is, a 100 watt light bulb ought to be enough to heat is up! Cannot imagine that the unit is not generating enough heat to have you cooking in there.

Charles

 

[mwbailey]

Charles, My thoughts, exactly! Shouldn't be that hard to heat up.

zmaxmotorsports, the 73 return was measured right at the top of the inside unit; 113 at the vent outlet. I didn't see the readings, but I don't think the guy was trying to hoodwink me. As I mentioned in an earlier post, this guy's company didn't install the unit, so he has nothing to hide.

I thought maybe somebody on GJ might have had a similar experience and could suggest a solution. I can't believe that this thing is messed up by the peaked ceiling.

 

[CJCar]

Where is the thermostat located? Does the unit seem to run full tilt all the time (compressor, not just the fan)?

 

[mwbailey]

CJCar, the thermostat is actually a remote, since the controls on the "high wall" unit are out of reach! We've tried a couple of locations with similar results.

The unit shuts off routinely -- not extremely short cycles, nor long cycles. The HVAC guy suggested that the electronics in the control system were sensing the 73 degree return air and even without the thermostat reaching set point, turned the unit off. I guess to some extent I could see this as a good "over ride". Maybe somebody forgot and put the remote in the refrigerator -- or closed it up in a drawer.

 

[bassbucket]

we're is your return in relation to supply could be to close together.

 

[JakeKohl]

I went through something similar. A couple of points are important to this:

A) the actual thermistor that senses room temperature is IN the air handler. If it's mounted up high and the warm air is up there, it will think it is warmer in the room than it really is. However, this shouldn't explain a 15 degree difference - maybe 4, maaaaybe 5 degrees F.

B) I couldn't tell what brand this is, but I installed two 1.5 ton LG units. They had a known problem with the remote control where the remote would read one temperature but send another to the unit. The remote reading and actual temp was about 10 to 12 degrees off - and worse in heat mode. Some of these units also have known issues with the thermistor that needs the thermistor replaced to get accurate readings. This problem on my units was made worse by the fact that the wall unit doesn't have any kind of temperature display - so I couldn't tell that it and the remote were talking a different language.

If your install guy was licensed, get him to work with the manufacturer to troubleshoot it. Otherwise call them yourself. I installed my own units and LG helped me with my problem really effortlessly and though I had to go through the company that sold me the units, LG gave me a ticket # to use through my vendor and provided new remotes. My problems have been gone.

BTW, my 1.5 ton units heat my two 850 sqft rooms EASILY even with the outside temps in the 20s. They kick out of idle ~maybe~ four times an hour and never go beyond medium speed. With a 35 degree outdoor temperature, it can take my (reasonably well insulated) garage from 64 degrees to 72 in about 8-10 minutes. They're pretty impressive.

 

[mwbailey]

Jake, Thanks; that's encouraging in a back-handed sort of way. Sounds like there could be some issues that need correcting, but at least your comments suggest there IS something that might be a fix! I was beginning to get concerned that what I had was NOT going to work. The guy that installed the HVAC died a couple of weeks after installation, so a different organization sent out a technician to check things out. It was interesting that the "replacement" guy suggested that the 73 degree reading at the return air might be cutting the unit off yet he moved the remote around -- I thought that meant the thermostat was in the remote.

On the other hand, the issues with the remote may relate to my problem. I'll have to check the brand and suggest looking into the remote.

bassbucket, the air return is on top of the unit and the air supply is on the front/bottom -- if that's what you mean. As a split, ductless unit, that's about what you get. I'm hoping the deflectors are designed to keep the thing from short-circuiting the air flow. . . .

 

[JakeKohl]

I didn't intend to be backhanded in any way....but I hope that helps.

 

[mwbailey]

Jake, No problem. YOU were not back-handed, but the encouragement for me was sort of like, "You got something that's broken." That's usually not something you want to hear, but in my case I want to find something to fix -- since it's not working, right?!

I'm headed to the workshop now to turn the remote up 10 degrees past what I really want, check the brand, and maybe give the manufacturer a call. You've given me a trail to follow!

Thanks again.

 

[CJCar]

A) the actual thermistor that senses room temperature is IN the air handler. If it's mounted up high and the warm air is up there, it will think it is warmer in the room than it really is. However, this shouldn't explain a 15 degree difference - maybe 4, maaaaybe 5 degrees F.

The t-stat being in the unit was my assumption as well. Looks like the unit is around 12 feet off the floor. I would not be surprised to see a 10+ degree difference from that height with a vaulted ceiling and being very well insulated.

I would have the ceiling fan blowing up at low speed 24 hours a day to pull the heat off the ceiling.

Also I would check to see if a remote T-Stat is available.

Chris

 

[mwbailey]

Chris, I'm getting ready to call the manufacurer -- checked it today and found out that it's a Carrier. I can't quite figure where the thermostat is since the technician mentioned the 73 degree return temperature possibly shutting the unit off yet he moved the remote within the room to see if it made a difference. Hope Carrier knows!

Yep, I'd give it about 12 feet off the floor. I leave the ceiling fan on low most of the time. Took some measurements with my Red Horse Saloon thermometer today before moving set point from 62 to 82 degrees and found temperatures throughout the room just about the same -- 58 degrees. When I changed the set point, the air coming from the unit was probably over 120 degrees! You'd think that would warm up the room. I'm back after lunch to check all that out.

 

[CJCar]

Chris, I'm getting ready to call the manufacurer -- checked it today and found out that it's a Carrier. I can't quite figure where the thermostat is since the technician mentioned the 73 degree return temperature possibly shutting the unit off yet he moved the remote within the room to see if it made a difference. Hope Carrier knows!

Yep, I'd give it about 12 feet off the floor. I leave the ceiling fan on low most of the time. Took some measurements with my Red Horse Saloon thermometer today before moving set point from 62 to 82 degrees and found temperatures throughout the room just about the same -- 58 degrees. When I changed the set point, the air coming from the unit was probably over 120 degrees! You'd think that would warm up the room. I'm back after lunch to check all that out.

Next time you take some temp readings, check at different heights: down at the floor, 6 feet, 12 feet. I bet you will see your set temp at 12 feet - same height as the unit and t-stat.

Did you leave the set point at 82 and the ceiling fan running from earlier?

You didn't mention, your floor is insulated, correct?

 

[pseudorealityx]

You need a thermostat located at occupant level. Also, at least with the Mitsubishi units I've dealt with, you have to select WHERE the temperature is measured... at the thermostat on the wall, or at the return air intake on the unit.

Also, I'm confused as to how your fan isn't evening out the temperature... Which way do you have it blowing?

 

[mwbailey]

Chris, I'm afraid I didn't do a good job of data-gathering; I didn't write it down and now I have too many numbers rolling around in my head. I had other things on my "to do" list this afternoon and didn't do a real thorough job. I'm back on it tomorrow morning (workshop is remote from house).

But, the floor is NOT insulated. However, it is 2 inches thick, and it is the loft floor inside the workshop with the 4-inch thick foam walls. I like the idea of floor level, 6 foot, and 12 foot temperature measurements. It will be interesting to see what floor level is.

Pseudo, There is no thermostat on the wall! There is a remote control that looks a lot like a TV remote that can be mounted on the wall, if desired. Right now it's just sitting on the countertop! I checked one time which way the fan is turning -- blowing up or down -- but now I've forgotten that, too. . . .

I called Carrier, but they referred me to a local HVAC group. Called them and they want to come out and check the unit. I'm sure they also want to charge me for the visit, but for the moment my builder sees this as something he needs to correct (and I agree). So, it's on his nickel. That's fine with me.

 

[brewchief]

Without know the exact unit it's hard to be sure but looking at a few manuals on Carriers site it appears the room temp sensor is in the unit, that would make sense given the problems.

The simple fact that it cycles on and off tells me it is satisfying the temp sensor, if it never shut off it would be a different story.

Get some temps at different heights, I think you will be surprised.

 

[pseudorealityx]

Without know the exact unit it's hard to be sure but looking at a few manuals on Carriers site it appears the room temp sensor is in the unit, that would make sense given the problems.

The simple fact that it cycles on and off tells me it is satisfying the temp sensor, if it never shut off it would be a different story.

Get some temps at different heights, I think you will be surprised.

Agreed. You need to talk to Carrier about retrofitting a separate temperature sensor that you can locate on a wall at occupant level.

 

[CJCar]

You are always going to have a temperature variation in regard to height, heat rises, it's stratification. No matter what height your unit is mounted at you will still see this. Use your ceiling fan to minimize it by mixing the air in the room. Most people set their fans to blow up when heating and down when cooling. Leave it running all the time on low.

Insulate your floor. The colder temp below is pulling heat from the room and everything in it - adding to the stratification effect.

It would be ideal to mount a remote t-stat. Opposite side of the room from the unit about 4' off the floor. However the temp variation with regard to height should be fairly consistant. Set your temp 10 degrees higher than what you actually want it to be until you get your t-stat installed.

When making changes or taking temp readings, keep in mind any change will not be immediate. Make small adjustments and give it an hour or so to test the results.

Chris

 

[mwbailey]

Well, I took some temps today and recorded them so I didn't have to remember them. Remote cointrol set point was 82.

Outside: 36-37
Inside workshop: 48
At floor in loft: 56
Countertop in loft: 60-62
6 feet in loft: 66-68
about 12 feet in loft: 72
At AC unit: 72-76 (this surprised me, but it IS at about 12 feet)
Exiting air from unit: 114

Looks like a good bit of difference between floor and 12 feet. I guess I'll look at insulating the floor although I hate to do it. The "other side" of the floor is V-ed tongue and groove. Really looks nice from down there. . . .

 

[CJCar]

Well, I took some temps today and recorded them so I didn't have to remember them. Remote cointrol set point was 82.

Outside: 36-37
Inside workshop: 48
At floor in loft: 56
Countertop in loft: 60-62
6 feet in loft: 66-68
about 12 feet in loft: 72
At AC unit: 72-76 (this surprised me, but it IS at about 12 feet)
Exiting air from unit: 114

Looks like a good bit of difference between floor and 12 feet. I guess I'll look at insulating the floor although I hate to do it. The "other side" of the floor is V-ed tongue and groove. Really looks nice from down there. . . .

The temp change from floor to 12' does not surprise me. Was the ceiling fan on the whole time the unit was set at 82?

What does surprise me is the 72-76 temp at the unit. What are you using to measure the temp and is it accurate?

I would expect the system to run non-stop until the temp at the unit was within a degree or so of the set point. Most t-stats have a 2 degree swing: if it's set at 82, it will call for heat at 81, run until 83, and then shut off.

Chris

 

[mwbailey]

Well, I'm using my Red Horse Saloon thermometer, of course! Actually, the HVAC guy double-checked it versus his fancy-dancy set-up and said it was right on! Here's the "precision" instrument in location for near unit measurement.

The HVAC technician didn't seem too alarmed with the data, but encouraged me to keep the ceiling fan running! which I have.

But I'm with you, Chris, I don't understand how this thing is controlled.

Turned the whole thing off when I left this afternoon -- partly due to frustration, partly because we're supposed to be in the teens tonight and I wasn't sure I wanted it running all night to no avail.

 

[green.bubbly]

Ceiling fans running in reverse would seem to be your solution. You gotta get that air blended. Perhaps install a fan near the unit blowing across the ceiling. Really sounds like the heated air is just pooling up around your unit.

On my unit, the thermostat is on the unit itself. Even with no remote, I can control the unit from its control panel. Of course it is a cheap unit and better units may have it in the remote.

I understand not wanting to insulate under your floors. Have you considered a thick carpet pad and carpet on the floor. Not a great R value but should help a good bit.

 

[JakeKohl]

Jake, No problem. YOU were not back-handed, but the encouragement for me was sort of like, "You got something that's broken." That's usually not something you want to hear, but in my case I want to find something to fix -- since it's not working, right?!

I'm headed to the workshop now to turn the remote up 10 degrees past what I really want, check the brand, and maybe give the manufacturer a call. You've given me a trail to follow!

Thanks again.

Broken is better than undersized and unworkable!

 

[mwbailey]

Jake, I'm wishing more and more that something was broken. Now I'm afraid that the design my be an issue. Maybe high wall, ductless, split system HVAC units are not compatible with peaked or cathedral ceilings. I haven't given up, yet, but I'm getting discouraged.

Green, I like the idea of a thick rug pad!!! And it seems that most folks think there's enough heat coming into the room; just not getting mixed well enough. The mixing may required a pretty high-powered fan!!

 

[Jackfre]

Carrier has sold a number of manuf units over the last several years. They do not manuf mini-splits. They private label them. Your is either a Tadiran (from experience, I hope not) or I think it is Toshiba who is currently making these for Carrier. No American AC manuf is making mini-split heat pumps. They don't know how! Sad, but true! As well, they are not committed to the technology and offer them just so they can get a piece of the market.

Your design is not right. The evaporator as Jake pointed out is to high. Shouldn't be over 8' from the floor. Also as pointed out, your remote is a communication device, not the t-stat. Again Jake is correct that your actual stat is mounted on the evaporator. The unit simply doesn't have the fan horsepower to get the heat to the floor. Physics win again! You may be able to get an optional t-stat to work on this. This depends upon the manuf and model of the equipment, but it will not solve the real problem of "to high" an evap. You could try the a ceiling fan but I think you might want to look at Fan-tech's in-line fans. Pull a duct from the peak and blow it across the floor.

Without a unit Make/Model size and also a location (where do you live) it is hard to tell if you should be really discouraged or not. Unlike men, not all mini-splits are created equal. I am most familiar with Fujitsu having them in my home and having represented them for years. They list their equipment by temperature as well as seer and hspf. Some units will heat down to -15f, some to 5f, some to 32f. Depends upon where you live and what your needs are. Carefully, get on a ladder and get the unit serial number and model number for both the indoor and outdoor equipment and post that. I have a friend I owe a call to who works for carrier. I'll see if I can get some info on it. Also, how is your outside unit mounted? Is it on the ground or raised off the ground. Raised is correct for a heating unit. Post a pic of that too.

 

[Jackfre]

Oops, Just saw the Rock Hill, SC.

 

[mwbailey]

Jack, et al., Yep, I'm begginning to believe the installation versus room shape is what's getting me. But, here is some of the information you asked about!
Model 40MVQ-012-101
Serial # 0412V02624

Makes sense that remote is sending unit, only. Just seemed funny that the HVAC guy wanted to move the remote to another spot in the room. . . .

We've been trying to avoid ducts and wiring showing -- check out build thread http://www.garagejournal.com/forum/showthread.php?t=156563, posts 88 and 89, for example. So, I want to avoid ducts in the loft, if possible. A heavier duty ceiling fan might be the ticket. At this point, I'm not sure lowering the unit to 8 feet is in the cards.

I haven't checked numbers on outside unit. Not only is it not on the ground, it's on the roof of the lean-to. The installer wanted to keep the lines less than 25 feet long. The unit is in the second floor loft. I don't have a ladder tall enough to get to the lean-to roof. Guess that will have to be a near-there purchase! First photo is shot through water sprinkler, so it's a little blurry.

 

[JakeKohl]

Jack, et al., Yep, I'm begginning to believe the installation versus room shape is what's getting me. But, here is some of the information you asked about!
Model 40MVQ-012-101
Serial # 0412V02624

Makes sense that remote is sending unit, only. Just seemed funny that the HVAC guy wanted to move the remote to another spot in the room. . . .

We've been trying to avoid ducts and wiring showing -- check out build thread http://www.garagejournal.com/forum/showthread.php?t=156563, posts 88 and 89, for example. So, I want to avoid ducts in the loft, if possible. A heavier duty ceiling fan might be the ticket. At this point, I'm not sure lowering the unit to 8 feet is in the cards.

I haven't checked numbers on outside unit. Not only is it not on the ground, it's on the roof of the lean-to. The installer wanted to keep the lines less than 25 feet long. The unit is in the second floor loft. I don't have a ladder tall enough to get to the lean-to roof. Guess that will have to be a near-there purchase! First photo is shot through water sprinkler, so it's a little blurry.

Hmmmmm...is that outdoor unit getting a deluge of water from the roof? That looks like an odd way to install it and prone to getting hammered in an ice storm (freezing rain) and generally get a ton of water washed through it in any rain. Most of these units have a specific line set length limitation - mine was 90 feet but I think that limit gets shorter as the unit capacities get smaller. That seems "interesting" that the installer preferred the shorter line set...and, is that untreated wood?

As far as the temperature issues go, I would investigate the possibility for a wired thermostat that you can mount on the wall at people level. Some of these do for around $50, $75...but, even then, I'm not sure they actually move the temperature sensing function from the unit to the thermostat level.

It's a great looking room, though! I would also try to correct the issues related to the heat pump before insulating the floor. The floor isn't going to affect the room as much in heat mode...see how it does cooling in the summer before ripping out your ceiling and going with more insulation.

It's starting to feel like a do-over on that installation is advisable.

 

[mwbailey]

Jake, First, the wood IS treated lumber and there are plenty of drain holes in the "bottom". I'll double-check the spacing, but I think the water from the roof will not hit the unit, but, of course, will find the "shelf".

I'm letting the builder look into the "do-over" part! That would be on his nickel. But, I'm ready to USE the room for my own enjoyment and don't really want to have to do major reconstruction. That's why I was hoping a simple fix like replace a broken controller, upgrade ceiling fan, or whatever, would get he there.

I got confused on the floor versus ceiling insulation. There's 6 inches of foam in the loft ceiling plus 7/8" shiplap board plus 1/2" OSB on foam panels plus shingles, wrap, etc. I'd hate to think that we needed more insulation in the loft ceiling. The "ceiling" from the garage (which is the floor of the loft) is 2 inches of tonge and groove. I don't want to spoil the "view" from the garage, but that could take insulation pretty easily -- installing batts.

We'll see what the builder comes up with!

 

[JakeKohl]

Jake, First, the wood IS treated lumber and there are plenty of drain holes in the "bottom". I'll double-check the spacing, but I think the water from the roof will not hit the unit, but, of course, will find the "shelf".

I'm letting the builder look into the "do-over" part! That would be on his nickel. But, I'm ready to USE the room for my own enjoyment and don't really want to have to do major reconstruction. That's why I was hoping a simple fix like replace a broken controller, upgrade ceiling fan, or whatever, would get he there.

I got confused on the floor versus ceiling insulation. There's 6 inches of foam in the loft ceiling plus 7/8" shiplap board plus 1/2" OSB on foam panels plus shingles, wrap, etc. I'd hate to think that we needed more insulation in the loft ceiling. The "ceiling" from the garage (which is the floor of the loft) is 2 inches of tonge and groove. I don't want to spoil the "view" from the garage, but that could take insulation pretty easily -- installing batts.

We'll see what the builder comes up with!

Yeah, I was talking about your tongue and groove "ceiling" from the garage - no need to mess with that yet. Good luck! I hope the builder comes through.

 

[pseudorealityx]

A big fan pushing the air DOWN will get rid of most of the stratification. The bigger, the better. That's the easiest, cheapest solution right now that will help.

 

[Jackfre]

The installer probably tried to keep the line set within the distance that the units factory pre-charge would handle. That way he doesn't have to weigh in refrigerant, 410A I'm assuming. The thing about supplemental wall t-stats is that not all models can be used and actually take over the sensing/control of the unit. you have to be very specific with that question. "Will this wall thermostat be in control of the temperature and is it compatible with this model?"

I called my friend and found out why he called me. He was informing me of his departure from that job. Sorry, but he was no help.

Air-tec, Diversitech and Sauermann makes the metal mounting brackets to support your evaporator. Where you run into trouble with condensing units mounted flat on a pad is that in the defrost mode the unit you will melt ice off the coil. If that moisture is allowed to run down and pool it will freeze and over time possibly build up and can actually get deep enough to freeze up to the condenser fan, at which point, well, you get the idea.

 

[mwbailey]

Hey pseudo, If the builder doesn't come up with a cure pretty soon, I think I'm pursuing a larger fan!

Jackfre, Thanks for advice on watching for freezing moisture. I guess I need to get that extension ladder so I can check things out.