Possibly a little of both, if the liquid line is warm/hot the condenser is probably dirty or condenser fan could be struggling/stopping.

 

Fan is fine. On my previous 20 year old Carrier recip I never had to have the condensor cleaned but with these new high SEER Scroll units I'm not sure what is required. Sure looks like a lot more coil fins packed closer together, but then again I can't honestly say I ever paid attention to the old recip enough to be able to say if there was a difference. Is there a particular temperature I should be getting on the liquid line that will indicate if I should call somebody out to check & clean the condenser coils? And would I measure at the AHU or the condenser? Is cleaning part of a basic service call or do I need to specifically request it?

Thanks for the help.

 

Thread relocated to AOP

 

If the air is the same temp out of the registers as before, than hte roof could be contributing, expecially if its' an attic installation. The change in ventilation would be the biggerst change. How many layers of shingles were removed? Additional shingle layers may have acted as a insulator and vapor barrier. A hot roof will drive humidity into an attiuc. IF hte equipemtn or ducts are in the attic, the increase latent load, combiend with less ventilation can make a big difference.

Now if hte air is significantly warmer, then your problem might be the condenser. ALL air cooled coils will need regular cleaning. I don't think the older equipment was any more or less sensitive to air movement across the coil. Higher refrigerant pressures from less heat transfer will result in less effciency and capacity.

It's also possible that yoru system developed a leak and it's jsut a coincidence that your seeing it now.

Liquid line temperatures are useless without knowing the pressures.

 

Hi,

Just had a new roof put on my home and noticed the AC seems to be struggling a bit during peak afternoon hours with about a 77 degree indoor setting. 3 ton Carrier Split heat pump system only 2 years old. Single story home, AHU inside a closet indoors.

I'm trying to determine if maybe the new roof (going from 3-tab to architectural shingles) and a 15# felt to 30# felt might be the issue trapping more heat. Same color shingles as before (medium gray). Another change is the ridge vent - used to be a standard aluminum 18 sq in/ft net free air and now is a high-performance plastic low-profile Lomansco with just 11 sq in/ft net free air. When there is wind it pulls well, but in stagnant air it obviously does not have the same net free air space to vent.

The other thing I noticed is the liquid line entering the AHU becomes warm when running at temps over 85 degrees outside. Below 80 degrees the line is very cool to the touch. Is this normal or reflective of a charge issue, TXV issue or dirty outdoor condenser coil fins? (Visually they don't really appear dirty or clogged)

At peak afternoon heat around 90 degrees outside the attic temps are now running about 30+ degrees greater than outside temps. (120-125 range)

SO.....question I'm trying to narrow down is this: Is the AC functioning okay or is the attic just excessively hot due to something related to the new roof, which is then possibly effecting the AC performance? This isn't a DIY but just trying to get a direction on this before calling anybody to look at the situation. I figured the HVAC experts may have ran into this kind of thing before. Many Thanks, Sonic

It is possible there could be a Return air leak allowing hot humid attic air getting sucked into the return.
Record the discharge air temperature coming off the outdoor condenser & then subtract the outdoor temp from it.

For the test to be meaningful, make sure the condenser is clean & dry before running the temp checks below.

At 90F outdoors & 75F & 50% relative humidity indoors the condenser air-temp-split should not be above 17F; @ 80F & 50% indoors the split should not be above 22F. If at 50% indoor RH & those temps, the temp-splits are above the listed split levels, it could be drawing hot air into the Return from a hot unconditioned space, like the attic. Hardware stores usually have low cost humidity gauges, every home needs one.

Especially, if it has a Return chamber under the furnace, every possible entry point must be totally sealed from any source of unconditioned air.

 

I'd say its a combination of a dirty condenser coil. And not enough ridge vent.

 

I'm calling a nail in the suction line!

 

I had that happen when i lived in a condo. Lineset was run up near the rafters.

 

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Many thanks to all who replied.

To clarify: One shingle layer, attic ducts, lineset under ground (under the slab).

I suspect a combination of slightly dirty condensor mixed with ventilation that is just not keeping up. Now, could be NEW heat generated by the new roof or it could be the SAME heat just not ventilating as well with the new ridge vent.

Not sure this provides a clue or not, but once the attic and outside cools to 80 degrees or less the A/C blows very cold as usual. It is when the attic starts exceeding about 110 degrees and the outside exceeds about 85 that the air from the ducts is not quite as cold, and so the system starts running a lot to keep up. It is still very cool, but not quite as cold. Perhapes I should do a Delta T test from intake to exhaust on the AHU?

The other possibility, as somebody pointed out, is maybe a slow leak. I did notice something today that I do not recall seeing before... On the liquid line where it connects to the drier outside of the condenser I am seeing what looks like little "blisters" in the copper at the braze joint. Would this by chance be a symptom if Puron had been slowly leaking? I will try to take a picture and see if I can figure out how to upload it....

 

Many thanks to all who replied.

To clarify: One shingle layer, attic ducts, lineset under ground (under the slab).

I suspect a combination of slightly dirty condensor mixed with ventilation that is just not keeping up. Now, could be NEW heat generated by the new roof or it could be the SAME heat just not ventilating as well with the new ridge vent.

The other possibility, as somebody pointed out, is maybe a slow leak. I did notice something today that I do not recall seeing before... On the liquid line where it connects to the drier outside of the condenser I am seeing what looks like little "blisters" in the copper at the braze joint. Would this by chance be a symptom if Puron had been slowly leaking? I will try to take a picture and see if I can figure out how to upload it....

its probably just excess solder on the joint, but a picture would confirm.

 

Sure would have been nice if you could have gone with a "cool roof" material. If you can't get the ducts out of the attic, and you can't insulate the roof deck, nothing beats a cool roof for reducing attic temperatures.

That said, if you haven't had your a/c serviced for the summer, do it now. If you get it working in tip top shape and it still seems to underperform on hot days, you then know your new roof and/or ridge vent may be the culprit. I'm not all that confident ridge vents reduce attic temps all that much, but they are better than nothing.

 

I'm not all that confident ridge vents reduce attic temps all that much, but they are better than nothing.

It would help if I had an idea of what a "normal" temp is for an attic in Florida with passive ventilation. Right now, I am seeing a 30 degree delta between the attic and the outside temps when at the peak heat of the day lately (about 90 degrees outside). So I'm reading ~120 degrees which seems ridiculously hot to me. I don't recall the attic feeling that hot before but then again I never measured it previously. Attic is about 10 feet high and I'm measuring at mid height, but higher up at the peak of the roof I bet the temp is at least 5 degrees hotter yet. Can't imagine what is going to happen when we get to the 95-100 degree range soon with high humidity....

 

Attic temps are mostly driven by the solar heat gain on the roof. The attic temp when it's 90F outside isn't a lot hotter than when it's 85F outside.... probably just 6-7F hotter in the attic. Humidity doesn't drive attic temps.

"cool roof' desings unfortunatly are pretty foreign to most roofers. Plus it's more expensive for the homeowner even though steel roofs last a lot longer and ithe cost difference will pay for itself within probably 10 years... less if you can use tax credits.

 

one thing I've seen on roofing redoos is changing from gable to ridge... and lack of airflow... soffit vents are where the air enters, ridge is where it exits...

if the house has gable, and ridge is added... the ventilation does not cool the attic...

since you had ridge before, likely this is not the problem, but I thought I'd mention it.

heavier shingles do retain more heat, and more heat has to go somewhere.

 

After climbing through the attic last night I found the last two rafter bays in the back corner of the house are not insulated, and after checking just now in the heat of the day the drywall on the ceiling feels very warm from below. This is a tiny amount of over all space of the house ceiling (about only 50 square feet at most, and has been this way all along. Hard to describe, but that area of roof in the back corner has an "extension" most of which sits on the real roof and they obviously couldn't get in there to blow insulation. I'll have to see if I can find somebody to do this, maybe go in through the side soffit or something. This is still only a symptom of the bigger problem though - which is either the attic ventilation or the AC.

Attached is the picture I promised. I wonder if those blisters are just copper rust. The effected area is in sunlight all day and directly under the drip eave so it gets rain and night condensation dripping on it. Maybe I should cover it with some insulation?

Please let me know what you guys think, if it is a likely indicator of a Puron leak...

 

Attached is the picture I promised. I wonder if those blisters are just copper rust. The effected area is in sunlight all day and directly under the drip eave so it gets rain and night condensation dripping on it. Maybe I should cover it with some insulation?

Please let me know what you guys think, if it is a likely indicator of a Puron leak...

View attachment 387221

in the picture, I see a copper reducer, and standard welding. I also see a small amount of rust on the dryer. I see nothing that would indicate a leak.

it looks like a poor job of welding, but it should not leak.

 

Am I seeing two driers (the blue and the black cylinders on the pipe) in line with one another? If so that might be part of your problem!

 

No, the black thing you see is just a rubber "seal" I put over the line because the line enters a black poly pipe before it goes under the slab. Since the line is under the drip eave I was concerned it may allow water to run down the line and into the pipe and fill with water over time, so I put a rubber stopper on the line to seal the pipe. It's a rubber foot used for chair legs, simply drilled a hole in the center, slit down the side and put it over the line & pipe.

 

Clever solution for the chase and pipe.

That orange spot appears to be light surface rust. If it bothers you, sand it off and apply a coat of shiny spray paint to protect the fitting.

Most of the time, if a leak was in this location, you would see and feel traces of oil on the surfaces.

 

Okay, thanks guys, that "blistering" is likely just traces of normal copper/weld oxidation I'm guessing.

I'm going to try and get a ventilation expert out to the house next to see maybe if he can give an expert opinion on the ventilation situation and what may be going on with the ridge vent in particular.