I think the unit is the correct size, i would say it was sized to maintain 78 degrees. See how it works if you set it to 74 and dont touch it. Shade your windows?
You guys probably hate questions like this, but I need to have some idea of whether I'm getting BS from the contractor.
I have a section of my house that is 624 sq ft (outside dimensions) which consists of one large room and one tiny bathroom. The main room has a ten foot ceiling. This room is less than two years old and seems reasonably well insulted: 2x4 walls with fiberglas batting and fiberglas in the ceiling that is at least 16" deep. Three of the four walls are outside walls.
During the afternoon, with outdoor temps in the high 80s or low 90s, the temp of the main room will not drop below 76-77F with the heat pump running continuously. The heat pump is a 1.5 ton unit installed less than a year ago. The air coming out of the ducts is about 58 degrees or so. The filter is new.
Given the duct temp, I'd say the unit is probably working ok which makes me think it might be under sized, but 624 sq ft doesn't seem too large for a 1.5 ton unit. I'm curious as to how much additional capacity is required for a 10 foot ceiling versus an 8 foot ceiling.
I'd be grateful for comments that might help me get a little perspective on this.
Thanks!
-Dave
I think the unit is the correct size, i would say it was sized to maintain 78 degrees. See how it works if you set it to 74 and dont touch it. Shade your windows?
Quality and Value Service and Repair
Is there a return in this room or is the return elsewhere, the split temps sound correct 20 degrees, it should cool down properly,according to what you posted, the scenario doesnt pan out, that room should be an ice box.How many air vents are there?
I have the thermostat set to 72. The unit runs continuously until the sun goes down, when it is finally able to catch up.
The room has four vertical sliding windows with double pane glass (36"W x 52"H), plus there is a smaller window in the bathroom (24"W x 36"H). The windows are all covered with white aluminum blinds that are closed so that no direct sunlight is coming it.
There are 5 ceiing vents in the main room and one in the bathroom. There is an additional vent in the stairwell, but I've had it shut while I've been experimenting. I also have both doors shut so the other parts of the house don't add any load to this system, although I don't see much of a difference whether the doors are open or closed.
The air intake is in the center of the ceiling of the main room and is 24"x24".
The temperatures of 76-77 are without any of the fifteen 75 watt recessed lights turned on. In fact, there is no electrical equipment generating any heat in the room.
This is a second story room and the rooms below are cooled.
The room is to be used as a part time photography studio and during a shoot, I am very actively moving around. At 77F, I'll be drenched in sweat.
Was I wrong in assuming that heat pumps are usually sized to get lower temperatures thn that? If this unit will only get the room down to 77, I'll have to get a bigger one. And I it's not even 2 years old! I had this room added to the house so I wouldn't have to shoot in the hot old garage anymore.
-Dave
Hmmm... I have pictures of the room on my website here in case it would help. It's the top 5 pictures. The pictures are through a wide angle lens, so the room might look a little bigger than it is.
http://www.kruegerphoto.com/studio.htm
-Dave
Are the fifteen recessed lights a sealed housing type, preventing air infiltration from the space above? If they are rated for direct insulation contact, they probably are sealed fairly well. If they are not rated for direct insulation contact, they are probably full of holes, allowing hot air from above to enter the space. Do you run the exhaust fan in the bathroom continuously? If so, it could be pulling hot air from above the recessed lights, through holes in the light housing, and into your space. Is there an attic or crawl space above the ceiling?
Nice studio. Is that pull down stairs in the center of the ceiling? Is there attic space up there? Can you see the recessed light housings from up there? How well are the pull down stairs sealed at the ceiling? Could be another air infiltration avenue.
The recessed lights are closed. They are rated for contact with the insulation and are in fact covered by it (by several inches).
The pull down ladder makes a pretty tight fit to the frame, but there is no weather stripping, if that's what you mean.
There is a floor in the attic adjacent the pull down ladder which is less insulated than the deep blown in insulation around it. I think there is batting under the floor. The ceiling joists are 2x8s and the batting is pretty thick.
The attic is pretty hot. In fact, I probably don't have a thermometer that goes up high enough to measure it. I'm guessing it might be 120-130F. How much help are attic fans? I have two large mushroom vents in the attic and numerous sofit vents. Replacing one or both of those vents with attic fans would have to be cheaper than changing out the heat pump. The air handler is up there, so it's subjected to that heat...
-Dave
Outside temp is 93F.
-Dave
You have a heat gain or an infiltration problem, you didn't mention a vapor barrier, are you direct sun light? what is your exterior material? do you feel a draft when it is windy?
If you have your photo equipment running and all those lights on i guess you have surpassed the ability of the unit to keep up. Maybe you could add a mini split to you room to assist the unit.
http://www.sanyo.com/industrial/HVAC/
Quality and Value Service and Repair
The walls are 2x4s with fiberglas batting. Sheathing is OSB with hardiplank (fiber cement) siding. No vapor barrier or house wrap. Interior is just regular 1/2" sheet rock.
I don't know if I would notice any infiltration during the summer, but we don't have any trouble keeping it warm during winter. I don't feel any drafts and the outside is well caulked with silicone. Of course, lap siding is not going to be completely air tight, but there's practically no furniture in the room so it's pretty easy to see there is no place that air is likely to get into the room from the outside. The windows seem to have a pretty good seal, as well.
I thought it strange that they didn't use any house wrap, but I thought they knew more than I did, so I didn't complain. In fact, I comepletely removed all the siding and sheathing from the old part of the house and replaced it with OSB and fiber cement so the whole house is now like that. But, the old part of the house isn't having a problem staying cool even with a 32 year old heat pump...
One thing I noticed is that you have to get your hand right up at the vent to feel much air flow. The old part of the house seems to blow harder through the vents. Maybe there's something wrong with the fan speed on the air handler...
Is it safe to say that under most circumstances 1.5 tons should be sufficient for a room this size?
-Dave
Market man,
I don't even have the room lights on. In fact, the only electrical equipment operating in the room is the thermostat and the fire alarm.
-Dave
If you've been having this trouble since it was installed, you should have had your contractor check it.
Have you changed your air filter lately.
There's water around the outside unit. I don't see it freezing up and a repair guy just charged it with coolant yesterday, but it seems like there shouldn't be any water out there. There's an identical unit right next to it for the lower floor and it doesn't have any water around it, but then it doesn't run constantly, either. It looks like the water is just condensing around the fitting for the copper coolant pipe that goes into the house. It has foam insulation around most of it, so not much is exposed, but there seems to be a lot of water considering the fact that it's 93F out there. The indoor unit drains in another place, so it's not from that.
-Dave
durning the day it cant keep up and when the sun goes it has no problem and cycles. you go into the attic and it is very hot about 130. i will bet it is even hotter then that in the attic on a 90 degree day. i would tend to think an attic fan would make a world of differance. with all the heat up there and the lights, and stairs you loosing
Nominal 1.5 ton unit is appoximately 16,500 to 18,000 btus ,at 95° outdoors (OD) and 80° indoors(ID),you are wanting 72°,that's 8° less than the standard rating ID.
To adjust for this,even if the room was sized for 72°ID,you deduct835 btus,per 1000 cfms,for every degree below 80°.
8 X 835 X .6(600 cfms divided by 1000 cfms)=4008 loss in sensible btus .
About a half ton of cooling,I'd guess the system is too small,and do the calculations and add a mini-split system ,cooling only as the heat is likely fine ,as is.
I wish I'd specified more clearly what my temperature requirements were before they installed the system. It just never occurred to me that they would install a system that ran constantly during the summer. That seems like it would wear the system out before long. I'm in Alabama. It's in the 90s during the day all summer long here.
I'm just not sure if this problem has existed since it was installed or is something new. I didn't use the room much for the first year, so I had the thermostat set to 74. However, I can't believe I wouldn't have noticed it not getting below 77F on warm days. Seems like I would have noticed it running continuously, too. If the problem is new, then something is wrong that can be fixed.
I'll put a meat thermometer up in the attic later today and see what the temp is up there. Yesterday, it was 93F outside when I guessed it to be about 130F in the attic.
I like the attic fan idea more than adding a split mini, but I did look up the Sanyo link. A small system would run on a 15 amp circuit, but I'd probably still have to run an additional circuit up there to do it. I might not need an additional circuit just to run a vent fan. I could also beef up the insulation. Some of it got trampled down when I had a roof leak a while back.
I appreciate all the comments. It will give me a better feel for what I'm dealing with without being totally dependent on what the repair guy says. By the way, the repair guy is from the company that installed it. That might limit his objectivity if the unit is under sized...
-Dave
Where in Bama??
Huntsville.
-Dave