hello, we just had centeral AC installed in our home. the home was built in the 50's and we live in Mi. the ducts are at floor level in the walls. our problem is that it doesn't seem like the house is properly cooling. the system is a 2 ton unit. I am being told now that the system is in that the duct layout is not good for AC but is good for heat. also I am being told that I need to install soffit vents and have our brick walls insulated ( I know the insulated walls are needed also for warming the home in the winter). I had read a little about people installing vents higher in the walls and using their studed sections for ducts to get the air to move thru the top vents. do you have any ideas on these issues? thanks in advance for any help that you can offer.
Robert

I see that I messed up my last post, I thought that I was starting a post and not replying to a post. guess I am confussed on how to start a post in this forum. sorry

A byproduct of air conditioning's cooling is the removal of moisture (humidity), so that's a giant leap forward especially when its running moreso during the day trying to keep the house cool. If you're in a humid climate, the humidity is sky high overnight and morning, yet it won't run much cause there's little need to cool. A single speed compressor is just fine, but a variable speed (2 spd) blower is mandatory. With a humidistat (see next post) the unit will run at slow speed wringing the moisture out.

A humidistat only costs maybe $100 for the part. Check with your contractor to verify but with mine.....I set it to a certain humidity % and as long as it is wetter than that inside.. the unit will automatically run at slow speed to extend the runtime before reaching the desired thermostat temp setting. Need a variable speed blower to do this. Works good in the morning when the unit may not go on cause there's little heat load but humidity is 85% outside. You have to play with it, cause if you have it set too low, it'll never shift up to high speed. During the hot day you want it running high speed for max cooling, and it will cycle enough that the air will dry out.

jake

I just installed 2 Honeywell IAQ Vision Pro tstats - and they do help control humidity. The IAQ tstats have a built in humidistat and you can program it so that even if the room temp is at the set temp level, the AC will still run (up to 3 degrees below set temp) to keep the humidity at the level you want. This is a great feature.

I was planning on connecting the IAQ stats to control my whole house dehumidifier which I put in the basement to handle a moisture problem down there. The Vision Pro has pairs of dry contact terminals that allows the tsat to control an external dehumidifier, as well as a humidifier and an ERV/HRV if you have those. However, as I was programming the tsat I noticed that you could set up the tstat to run the AC to work as a DH also. I tried it and it works great. So now the basement DH handles moisture down there and will provide some help with humdity upstairs too. But when it gets really humid, the tstats upstairs fire up the AC and provide additional dehumidification. I works really well.

srercrcr, sniffdog -
Thank you for your responses.

I would really appreciate if you can also share details about your HVAC system which are running with these humidity control tstats.

The issue that occurs with residential systems is that humidity is removal is secondary to cooling.

Anything you do to run the system more for humidity removal is going to drop the temperature.

Large systems cool the air for humidity control, then heat it back up to the desired temperature.

It costs $$ to install and run these systems, but they do a great job of humidity and temperature control (and most have outside air requirements).

They have actual variable refrigerant metering (more than just a TXV), variable speed blowers, and a whole pile of high dollar equipment.

Residential systems have at least moved up a little with the dual compressor setups.
Big for a lot of cooling, small for longer operation to help remove humidity.

Happy to help, it is a fascinating, and ever-learning, subject. My system is now 13 years old, a Carrier SEER 13 30,000 btu single speed scroll compresssor. The matching Carrier furnace and coil are variable speed propane. The humidistat (HS) is separate and mounted behind the return air register. Our climate now is humid and highs around 100, it cools my first floor of 1320 sf. At the peak of the day it runs like 20 min on and 20 off with it set for 77, the house is shaded, has porches, good insulation etc. Overnight gets very humid outside, like 85%, so I have the HS set so the blower runs slow for like four minutes then kicks up to high speed, this being with it set for 74 degrees. This is a reminder to me it is operating correctly. If I set the RH too dry it will stay on slow speed too long and my SEER 13 is out the window.The upstairs is only cooled/heated when I have company. I just got my highest electric bill and it was a whopping $135 (1025 kwh)and that's with paying a higher rate for supporting wind energy.

srecrcr and sniffdog,

We are in South Florida and only have today to make changes on an installation happening tomorrow. Needless to say, controlling humidity is a big issue to us.

Could you take a look at our thread and confirm that "we're good" or other things we may want to consider? We'd appreciate it!

http://ths.gardenweb.com/forums/load/hvac/msg0810071925522.html?3 (Good price on 2-unit Trane)

Thanks!

jake

I have a geothermal HVAC system. It is a 12 ton system with 3 Econar Geosource 2000 heat pump units. The loop field is horizontal and shared by all 3 units. I have 2 pumps for the loop system - one primary and one backup. One 3-ton and 1 6-ton unit cover the basement and main living areas - we have a master suite on the main level. I have another 3-ton unit to cover the second floor bedrooms which are almost never used.

I have a Sante Fe whole house de-dumidifier in the basement and 2 Honeywell bypass humidfiers on the 2 hvac units in the basement.

In September I will be installing a Broan Energy Recovery Vent with HEPA filter which should complete the HVAC system - finally.

I have 2x6 construction with blown cellulose insulation. Anderson A400 windows and doors. The entire house was caulked on the inside and every nook and cranny not covered by the cellulose was foamed. We also have spray foam in the joist cavities (where cellulose dosn't stick too well) and the attic has 11 inches of cellulose which gives us an R38 barrier. The house is in the mid-atlantic region and in the mountains at 1200 feet elevation.

When my system as installed by the builder, it did not have the humidifiers, dehumidifier, or ERV - all of which should have been part of the system. After several issues (dry air in winter, then damp floor in basement during the summer) I luckily I found this forum and learned what needed to be added to make it right. The Honeywell VP IAQ tstats are fantastic. I think Honeywell could improve the documentation - but rhe functionality is incredible for the price.