- My Forums
- Tiger Rant
- LSU Recruiting
- SEC Rant
- Saints Talk
- Pelicans Talk
- More Sports Board
- Fantasy Sports
- Golf Board
- Soccer Board
- O-T Lounge
- Tech Board
- Home/Garden Board
- Outdoor Board
- Health/Fitness Board
- Movie/TV Board
- Book Board
- Music Board
- Political Talk
- Money Talk
- Fark Board
- Gaming Board
- Travel Board
- Food/Drink Board
- Ticket Exchange
- TD Help Board
Customize My Forums- View All Forums
- Show Left Links
- Topic Sort Options
- Trending Topics
- Recent Topics
- Active Topics
Started By
Message
Any HVAC Professionals?
Posted on 5/7/19 at 2:59 pm
Posted on 5/7/19 at 2:59 pm
I just built a house and the builder installed Lennox equipment.
My inside Humidity has been over 70% and it feels quite muggy inside. (I'm in Austin, TX). I got to snooping around the units and I have a 2.5 TON outdoor unit and a 4 TON indoor unit. Is it common to not having matching inside and out? Building is sending a contractor to take a look but figured i'd ask on here.
My inside Humidity has been over 70% and it feels quite muggy inside. (I'm in Austin, TX). I got to snooping around the units and I have a 2.5 TON outdoor unit and a 4 TON indoor unit. Is it common to not having matching inside and out? Building is sending a contractor to take a look but figured i'd ask on here.
5
Posted on 5/7/19 at 3:07 pm to MayhemMike
Spray foam insulation? What's the square footage?
Posted on 5/7/19 at 3:17 pm to MayhemMike
Many things could be wrong here....
first question I have is, is the 4 Ton unit just the size of the air handler or is that the size of the coil?
If that is the size of the coil, then yes that can contribute to the humidity levels because it would have very little latent cooling capacity. The interior coil won't be getting cold enough to pull moisture out of the air.
If the indoor coil is sized properly (2.5 ton) then it could be just a CFM setting issue. This would mean they have set the CFM level in the AHU too high resulting in no latent cooling capability.
EDIT: Is it common? Yes. Many times manufacturers can pair a larger interior coil with a smaller outdoor unit to increase the SEER rating. The cost of doing this is losing de-humidification capability (or latent cooling). Most of the time though you would only see a mismatch of 0.5 to 1 ton. 1.5 ton would be a drastic difference.
first question I have is, is the 4 Ton unit just the size of the air handler or is that the size of the coil?
If that is the size of the coil, then yes that can contribute to the humidity levels because it would have very little latent cooling capacity. The interior coil won't be getting cold enough to pull moisture out of the air.
If the indoor coil is sized properly (2.5 ton) then it could be just a CFM setting issue. This would mean they have set the CFM level in the AHU too high resulting in no latent cooling capability.
EDIT: Is it common? Yes. Many times manufacturers can pair a larger interior coil with a smaller outdoor unit to increase the SEER rating. The cost of doing this is losing de-humidification capability (or latent cooling). Most of the time though you would only see a mismatch of 0.5 to 1 ton. 1.5 ton would be a drastic difference.
This post was edited on 5/7/19 at 3:20 pm
Posted on 5/7/19 at 3:30 pm to notsince98
quote:
1.5 ton would be a drastic difference.
I agree. I had a Lennox 4 and 5 ton system paired on the last house I built and it worked fine. I didn’t even know that they were different sizes until it came up on an inspection when I was selling.
If you look up your specific model number’s manual online it will tell you which model coils and condensers are supported to be matched by Lennox.
Posted on 5/7/19 at 4:57 pm to MayhemMike
In addition to comments here you can post your question and get responses from multiple HVAC professionals on this site. Of course the more information you can provide, model numbers of condensing unit, evap coil in the air handler, square footage of house, etc., the better, more detailed answer they can provide.
HVAC-TALK
HVAC-TALK
Posted on 5/8/19 at 7:08 am to CrawDude
Thanks for all the responses everyone. Here is some more info.
1580 sqft house
Outside Unit:
M/N 14ACXS030-230A23
Inside Unit
Model #: CX35-48B-6F-2
1580 sqft house
Outside Unit:
M/N 14ACXS030-230A23
Inside Unit
Model #: CX35-48B-6F-2
Posted on 5/8/19 at 8:10 am to MayhemMike
quote:
Thanks for all the responses everyone. Here is some more info.
1580 sqft house
Outside Unit:
M/N 14ACXS030-230A23
Inside Unit
Model #: CX35-48B-6F-2
OK. This one is a bit complicated. Your builder or HVAC guy may not be too helpful. Depends on how good their customer service is. There are 2 issues that matter in this situation:
1) This is a listed match in the AHRI directory. Here is a link to an AHRI certificate for one like yours. If you know your furnace model #, I can get the exact one for your system: LINK
Since this is a fully matched system, there isn't technically anything wrong with the system that is installed as far as parts go most likely.
2) This system is matched with an oversized indoor coil to squeeze as much SEER out of it as possible. Your AC unit is only 14 SEER but matched with this oversized indoor coil you are getting 16 SEER. This is great as far as energy savings go but it is TERRIBLE as far as comfort goes because it cannot remove humidity at all under marginal loads.
Possible solutions:
1) I'm going to guess the first attempt your HVAC guy will try is reducing the CFM setting. Less warm air across the indoor coil will allow the coil to get colder. The colder the coil gets, the more water condenses on it and the more humidity it will pull from the air. Depending on CFM requirements for proper air distribution throughout your home, this could work or it might end up starving an area of your home with lack of air flow.
2) To get better humidity control might require a different indoor coil. The CX35-30B or CX35-30/36B might be a better option. It should work with your existing furnace. Odds are your installer probably won't want to eat the cost of replacing the coil.
Good luck. I have been in your situation before. I had to force my builder to completely replace my HVAC system because EVERYTHING was sized way too large for my home. Credit to my builder and HVAC guys, though. They did it at no cost. They did not refund me the cost difference for going to a smaller system but at least I have a properly sized and comfortable system now in my new house.
Posted on 5/8/19 at 9:13 am to notsince98
Good answer/nice explanation.
OP as another poster asked does your new house have spay foam insulation in attic/walls? I know we are not yet in the heat of the summer but when your HVAC runs does it cycle frequently (i.e. have short run times)? Do you know if your builder had a Manual J load calculation done ( used to size the unit) and as I understand is now required by code. You need to ask to see the manual J load calculation for your new home to see if the unit is sized correctly.
On the HVAC-TALK forum I mentioned in my earlier post, I know a common theme among the HVAC professionals is that the most common problem they encounter in poorly preforming HVAC units, including new construction, is oversized HVAC units and undersized/poorly installed duct work. And they say builders have a tendency to over-size the units even when the Manual J load calculation tells them differently.
I’ve also seen some videos on HVAC issues associated with new installs where the problem was as simple as the unit being overcharged or undercharged with refrigerant, or as mentioned by Notsince99 where the indoor air handler blower speed was/is not properly set. Sometimes it’s 2 or 3 issues acting in concert with each other. Hopefully your problem is a simple one that is easily resolved by the HVAC installer.
When you get the problem resolved bump this post and let us know that the problem was and how it was fixed.
OP as another poster asked does your new house have spay foam insulation in attic/walls? I know we are not yet in the heat of the summer but when your HVAC runs does it cycle frequently (i.e. have short run times)? Do you know if your builder had a Manual J load calculation done ( used to size the unit) and as I understand is now required by code. You need to ask to see the manual J load calculation for your new home to see if the unit is sized correctly.
On the HVAC-TALK forum I mentioned in my earlier post, I know a common theme among the HVAC professionals is that the most common problem they encounter in poorly preforming HVAC units, including new construction, is oversized HVAC units and undersized/poorly installed duct work. And they say builders have a tendency to over-size the units even when the Manual J load calculation tells them differently.
I’ve also seen some videos on HVAC issues associated with new installs where the problem was as simple as the unit being overcharged or undercharged with refrigerant, or as mentioned by Notsince99 where the indoor air handler blower speed was/is not properly set. Sometimes it’s 2 or 3 issues acting in concert with each other. Hopefully your problem is a simple one that is easily resolved by the HVAC installer.
When you get the problem resolved bump this post and let us know that the problem was and how it was fixed.
Posted on 5/8/19 at 9:18 am to CrawDude
That is a good point about possible oversizing. That would definitely contribute to this problem. I didn't think much about it because 2.5 ton in Austin "seems" like a relatively small unit given the hot climate.
Posted on 5/8/19 at 9:49 am to notsince98
I’m going to have to replace my 14 year HVAC system in the next year or 2 so I’ve been “researching” this stuff to death. On face value doesn’t seem a 2.5 ton unit would be oversized for a 1,500 ft2 house in Austin. Installers use to use as a rule of thumb 1 ton per 500 ft2 of living area, and apparently many still do, but in today’s construction of tight houses, using spray foam insulation, etc. I understand 1 ton per 800-1,000 ft2 is not uncommon in a very tight, energy efficient home. The manual J load calculation provides the builder/HVAC installer with sizing information they should be using.
As an aside, I’ve seen multiple post from Austin homeowners on the HVAC-TALK forum. Seems like they have worst heat and humidity problems than we do in southern Louisiana.
Anyway, I know it’s not a funny issue for the OP, hope his problem is an easy fix.
As an aside, I’ve seen multiple post from Austin homeowners on the HVAC-TALK forum. Seems like they have worst heat and humidity problems than we do in southern Louisiana.
Anyway, I know it’s not a funny issue for the OP, hope his problem is an easy fix.
This post was edited on 5/8/19 at 9:56 am
Posted on 5/8/19 at 10:03 am to CrawDude
I can't speak for the attic but the walls have the normal strips of cotton candy insulation in them. I got a recommendation from another hvac installer about making sure they used a smaller expansion valve since they mismatched the units. It could help.
I'll let you know what the original hvac installer says when they meet with me. They are already being rude and saying the parts are correct and there is nothing wrong without even coming out. Their soultion was to turn my ac cooler to take the humidity out.. I have it set at 71 with 74% Inside Humidity..
This will most likely be a battle.
I'll let you know what the original hvac installer says when they meet with me. They are already being rude and saying the parts are correct and there is nothing wrong without even coming out. Their soultion was to turn my ac cooler to take the humidity out.. I have it set at 71 with 74% Inside Humidity..
This will most likely be a battle.
Posted on 5/8/19 at 10:57 am to MayhemMike
As others have said, lots of variables. Number and size of windows, insulation, direction your home faces the morning and afternoon sun. Your contractor should have run a Manual J load calculation. Takes all this into the sizing of the system.
Posted on 5/8/19 at 11:06 am to CrawDude
quote:
I understand 1 ton per 800-1,000 ft2 is not uncommon in a very tight, energy efficient home.
Sometimes it isn't even that much and you don't need spray foam.
I'm a bit further north but our design temp is still fairly high. I have 2,400sq ft above ground level with BIBS (blown in blanket fiberglass) in my walls which gives me R15 and reduces infiltration quite a bit compared to fiberglass batts. That alone got me down to 1.6 tons of cooling load. So I am at about .7 tons per 1000 sq ft.
Posted on 5/8/19 at 11:09 am to MayhemMike
I have watched some YouTube videos where cooling problems was associated with incorrectly sized or faulty thermal expansion valve (TXV) or fixed piston/orifice, depending upon what your unit has, a TXV or piston/orifice. In fact a HVAC tech from Louisiana who post videos widely on YouTube posted one on cooling problem his personal new “used” house was having and the problem was an incorrectly sized expansion valve which he had to change out to the correct size to fix the issue
Sounds like you might need to pay a couple hours labor for a highly experienced HVAC tech to come and check your system. Maybe you’ve found one in the other guy you talked to.
I was going to ask if you’re sure your humidity meter is correct but your definitely going to feel humidity that exceeds 55-60%. Hopefully it’s going to be a simple fix and not a sizing issue. If you have pink fiberglass insulation in walls you likely have that in the attic but you should check. Is your air handler is in the attic or is it a closet in the conditioned area of the house?
Sounds like you might need to pay a couple hours labor for a highly experienced HVAC tech to come and check your system. Maybe you’ve found one in the other guy you talked to.
I was going to ask if you’re sure your humidity meter is correct but your definitely going to feel humidity that exceeds 55-60%. Hopefully it’s going to be a simple fix and not a sizing issue. If you have pink fiberglass insulation in walls you likely have that in the attic but you should check. Is your air handler is in the attic or is it a closet in the conditioned area of the house?
Posted on 5/8/19 at 11:15 am to CrawDude
Air Handler is in a closet in my laundry room. The HVAC pros that have been giving me advice are back in Louisiana unfortunately.
The system also has a Honeywell "Whole Home Ventilation" system that was set to optimal ventilation. I think it was always bringing in fresh air. I turned it off so maybe it will circulate the same air and condition it.
The system also has a Honeywell "Whole Home Ventilation" system that was set to optimal ventilation. I think it was always bringing in fresh air. I turned it off so maybe it will circulate the same air and condition it.
Posted on 5/8/19 at 11:23 am to MayhemMike
quote:
The system also has a Honeywell "Whole Home Ventilation" system that was set to optimal ventilation. I think it was always bringing in fresh air. I turned it off so maybe it will circulate the same air and condition it.
That is a key piece of information too. Do you know why that was installed? Outside air ventilation is fairly rare in homes with fiberglass batt insulation. you should have enough infiltration to not need a ventilation system.
Posted on 5/8/19 at 11:43 am to notsince98
No clue why it was installed. I'd have to ask the builder/hvac installer. I found the panel for it while looking up model/serial number on the inside unit. I've had it turned off since 5am this morning.
Posted on 5/8/19 at 11:45 am to notsince98
Yep, that’s why the manual J load calculation is so important to sizing the unit. In contrast, I have a 4-ton single stage 14 Seer unit for 2,465 ft2 living area (house built in 93), about 600 ft2/ton. R-13 walls and R-30 attic - southern Louisiana. I recently used a online J load calculator to estimate my needs and it calculated 3.5 tons so I currently may be a tad oversized with my current system. But I can truthlfully say I’ve not had any cooling/heating/humidity issues, but I’m not as likely as efficient as I could or should be.
But I will hire someone to conduct a proper blower door manual J load calculation and Manual D (duct sizing) to identify and correct any significant air leakage issues I might have in the house envelope, and potentially the duct work, before sizing and installing a new HVAC system.
FWIW, I’ve pretty much convinced myself to install a whole house dehumidifier when replacing the HVAC.
But I will hire someone to conduct a proper blower door manual J load calculation and Manual D (duct sizing) to identify and correct any significant air leakage issues I might have in the house envelope, and potentially the duct work, before sizing and installing a new HVAC system.
FWIW, I’ve pretty much convinced myself to install a whole house dehumidifier when replacing the HVAC.
This post was edited on 5/12/19 at 9:25 am
Posted on 5/8/19 at 12:03 pm to MayhemMike
Yes, that interesting - whole house ventilation. Problem might be associated with that. I’ve watched a couple videos on those systems.
Here are videos by Matt Risinger a builder from Austin. Check his playlist on HVAC best management and house ventilation. Watch the ones you think are most relevant to your issue.
LINK
LINK
Here are videos by Matt Risinger a builder from Austin. Check his playlist on HVAC best management and house ventilation. Watch the ones you think are most relevant to your issue.
LINK
LINK
This post was edited on 5/8/19 at 12:28 pm
Posted on 5/8/19 at 12:43 pm to CrawDude
quote:
FWIW, I’ve pretty much convinced myself to install a whole house dehumidifier when replacing the HVAC.
Trying not to derail the thread and I know humidity is bad down there but do you think you need that? What indoor humidity levels do you regularly see now?
If you want just a tad better humidity control, I would highly suggest making sure your next furnace or air handler has an variable speed ECM blower with proper thermostat. You can set it up to reduce blower CFMs when humidity is above a setpoint. this reduces humidity faster and allows better humidity control during marginal cooling times.
Despite all that, a properly sized system set to 350CFM/ton would probably control your humidity very well.
Page 1 of 2
Popular
Back to top
Follow TigerDroppings for LSU Football News