Went to a hair salon today where my employer changed out an old 5-ton gas pack for a new one back in mid-April. The tenant in the space is complaining of high humidity in her space since the new unit was installed. She had PERGO type wood flooring installed at some point in the past and the floor boards are now buckling severly and paper products are becoming limp, curling and wrinkling all throughout the space.
They're also complaining that the cookies they leave out for snacking are getting very soggy. They are very NOT HAPPY about this!
In the space today I found that the floor is indeed buckling way too much.
We put some data-loggers in the space from last Wednesday afternoon until about noon today.
The graphs from the loggers show some severe swings in humidity and temperature throughout the period. Values are as follows.
Front of space/reception area:
Temp Min 69.20 deg. F Temp Max 78.68 deg F
RH% Min 54.8 %RH RH% Max 80.06 %RH
Rear of space/Wash Station-Hair drying area
Temp Min 69.59 deg F Temp Max 79.36 deg F
RH% Min 52.31 %RH RH% Max 78.18 %RH
Above Drop Ceiling next to Front Return Grille
Temp Min 69.79 deg F Temp Max 79.95 deg F
RH% Min 52.72 %RH RH% Max 76.38 %RH
If you can imagine the graphs as a saw toothed wave, the Temperature and Humidity readings are moving in opposite directions during the 24 hr periods of the days. When the temp decreases, the humidity rises. And, when the temp rises, the humidity decreases.
I took our balometer and checked airflow volumes between supplies and returns and found one problem. There are 859 cfm's of air coming from all the supply grilles and only 596 cfm's of air through the return grilles. The supplies are all 6" round runs with a 6' flex run to the lay-in grilles. They average about 72 cfm each.
There are two 24x24 lay-in return filter grilles for 20x20x1 filters with a 14" flex run each to the return plenum under the unit. There were 1" pleated filters in the grilles with 2" pleated filters in the RTU. I removed the 1" filters from the grilles. I still don't have enough return airflow.
I checked on my Ductulator and found that the return plenum needs to be 15" x 20" and that is what it is into the unit. With two 14" return runs to the plenum, there should be plenty of return air.
I have opened the sheave on the blower motor as far as I dare to slow the blower and give the evap coil a bit more ability to collect the latent heat from the air. I helped another tech a few days ago and we found the set-screw on the adjustable sheave had worked loose and spun itself shut running the blower too fast and drawing moisture off of the evap. coil. We do not have a tachometer so I can't reference the fan curve to see what is happening with the blower.
I checked the ductwork and did not find any leakage anywhere I could look. Unfortunately, it's a bit higher off the floor than I can reach even with a ladder, it was a visual inspection mostly.
Where the plenums joins the bottom of the RTU, both are well sealed. I probed around with a small wire and met resistance all around the perimeter, no openings.
There is a fresh-air intake on the return panel of the unit, it has been completely closed.
I do not find any problems with the refrigeration circuit of this unit. It's a CARRIER 48TFD006A511, Serial# 1604G20288. My ODA was 92 deg. F and my pressures were 265 psig high and 82 psig low. My return temp was 77 deg F and the supply was 58 deg F. These were taken at the unit, across the coil. On the grilles inside I only got an 11 deg F Delta-T. All the ductwork is insulated. I didn't take SH and SC as I felt they were not necessary for this problem. The unit is removing as much moisture from the air as it can, good pee-stream from the condensate drain and, it is removing a fair amount of heat from the space as the air from the condenser coil was rather warm. Hands-on measurement, didn't use the thermometer. I am concerned about the 82 psig suction pressure with the 77 deg F return air temp. The pressure seems a bit high for that temp. This unit has a metered header leading into the evap coil, no restrictions there. There were no leaks of outside air into the unit that I could find except for the screw slots on the fresh-air damper on the return panel. Those slots are 1/4" wide and about 3-4" long, with a gasket behind them. Shouldn't be enough infiltration to be a concern.
The tenant is past becoming upset about this and has told me that she is going to call her landlord and tell them she is leaving the space if the problem is not corrected. According to the tenant, there have been 8 seperate service techs out there to work on this problem and I'm No. 9. She's very unhappy with the service she is getting and the fact that her expensive new floor is coming apart and also causing people to trip from the pressure ridges.
My biggest concern is, where is all this extra latent heat coming from and how can I get rid of it? And, why were there no problems with the old unit and this one is nothing but a problem? The old one was replaced due to a lightning strike and the new one has been hit twice since install, I've been told. The old one was a CARRIER also so, keep the derogatory comments to yourself please. I've only been on this one twice and I thought I had it the last time. I was wrong!
I apologize for the length of this read. I figured giving all the info I had would be helpful to those who can help me. I appreciate all attempts to help me solve this problem. THANK YOU!!