RH Humidity Problems - Help!
I'll try to keep this as short as possible.
I have a 3,000 sq ft ranch style home in western Canada. We had new AC system installed 5 years ago, including ductwork in the attic of our home. 2 AC units were installed, (both 3 ton). One provides cooling for the LR/DR/Hallways and Den and the second does the bedroom wing. From day one we got extremely cold air and excessive cycling. In addition, the RH was never lower than 62%. After some discussion with the contractor, it was discovered that the manual J called for 4.2 tons (Supplier of the equipment did the manual J but didn't provide it to the contractor, just the recommendation for 6 tons) . The contractor discovered that the air handler for the LR unit was sized for a 4 Ton unit as was the duct work. The bedroom air handler was for a 3 ton and the ductwork was also sized for a 3 ton.
After a meeting last month the contractor said the following was the fix:
1. Remove the bedroom 3 ton unit and replace with a 1.5 ton unit and matching 1.5 ton air handler;
2. Remove the 4 Ton air handler from the LR unit and discard. Use the 3 Ton air handler (from the bedroom unit) connecting to the 3 ton outdoor unit - existing (this set up will give 4.5 ton of cooling capacity);
3. Balance air flow and adjust ECM air handlers to optimum speed.
With this new setup, cooling comfort has improved. Airflow has been reduced significantly and we no longer feel blasts of cool air (the "meat locker" effect). There was some discussion during the recent installation that we might not have enough "static pressure" with the new setup given that the ductwork was 3 ton for a now 1.5 unit compressor (bedrooms) and 4 ton for 3 ton compressor (LR/DR/Den). We had no further discussion on this.
I had asked the contractor to make sure they sized the new units correctly and asked that they upgrade me to 2 stage units. I reasoned that in off peak running times, the Rheem units running in stage 1 would dehumidify without lowering the temperature much below the set point on the thermostat. They said the cost would be excessive as their remediation plan involved using some of the same equipment, wiring, setup, etc.
I don't know where to turn at this point for a solution. I feel the RH of 63% when the outdoor is 60%RH (+28C) is too high. Crackers in our cupboards are soft and it just feels "wet" in the house.
Anyone have ideas as to what is wrong with out setup and what it will take to correct it?
RIGHT SIZING Equipment to Control Humidity Problems
Allow me to shock U concerning some sizing realities in your climate toward controlling humidity.
I live in SW Wisconsin today 9/4/12 at 2-PM at Lancaster it was 90F & 54% RH; indoors it is 52% RH & 76F with good air circulation & totally comfortable.
Lancaster, WI very close to me, at 3-PM on the hour updates, it was 91-F; 50% RH; Heat Index: 97-F. NOW at 3:26 PM it's 50% RH in here on my first floor area & 76-F; around 25-C.
The indoor contains 45.7 gr/per/lb/air; outdoors 116 gr/per/lb/air; A/C has to remove 45.7 gr//per/lb/air to get to 52% humidity level indoors.
This is a 1937 farm home loaded with 13 windows on 1st floor &, NO shade until very late in the afternoon; first floor area 620-sf have a Half-Ton window shaker with an adjustable floor fan positioned to move air through all the rooms & back to the A/C.
Okay, 620-sf divided / by .5 (1/2-Ton) is 1240-sf per/ton of cooling.
3000-sf / 1240-sf per/ton of cooling is 2.4-Ton; :grin2:
3000-sf home (however, your climate should be milder in western Canada than here in SW WI).
Well, U would have duct losses, etc., however, your home is way, way better insulated & protected from radiant & convection heat transfer than my home!
I have a Half-Ton on the 2nd floor which I only use in the evenings...
These small units have kept me perfectly comfortable in 112-F Heat Index.
How in the world could anyone 'initially' oversize equipment by that much?
Your home's calc should not be near where they had figuring it; even now it's still oversized for effectively controlling humidity plus meeting the sensible load.
I've never had a load calc performed on my home by me or anyone else; however, these light weight units do the job perfectly & use less wattage than most indoor blowers use!
It is amazing how much U can effectively cool with small tonnage; my all electric home monthly bills would shock your shoes off!:grin2: