Hey all, I have a 4 ton Goodman GMVC950905CX 2 stage variable speed unit w/ 2 zones set up on electronic dampers on a 2 story house in Richmond, VA. House is about 4 years old, insulated well, wrapped, etc. Ever since we bought the house, the air condition has come on very loud when one zone calls...and even kind of loud when both zones called. There is a bypass, but I think it needs to be adjusted (irrelevant for this topic). My question is, what is the best way to reduce the air flow and also help our humidity issue. With my hygrometer, humidity often reads 60-72% here in the summer, which is greater than even outside. My feeling is, A/C kicks on so hard that it satisfies tstat to quick...the run times are very short, not amounting to dehumidification. We had a tech come out this weekend to "tune up" the heat pump since our energy company offers a rebate for such. I also asked him of my problems. He offered to turn down the blower speed..which was set at 1470+10% to 1470-10%. This made AC quite nice when both zones call, but when one zone calls it is still loud, and it didn't seem to help humidity all to much (again bypass still needs to be adjusted which could help when one zone calls). Recent research has revealed that there is a DEHUM feature that can be wired which turns down speeds 15% when only one zone calls. Is this smart? My father in law just today recommended that maybe we try to disable stage 2 cooling since our 4 ton unit is likely oversized for our 2300sqft 2 story house anyways. Stage one is 70% which would make the unit operate like one that's just under 3 ton. This would result on longer run times and therefore less humidity. He also suggested turning the speed down to a fixed 1100 (since would only be 1 stage)...that would leave about 275cfm per ton when the manual suggest 400. Is this a problem? Is this a reasonable solution? Running the numbers...if we set the blower to 1470-10% which it is already, then use the dehum feature which lowers speeds 15% when one zone calls, that would put it at about 1100cfm right there, with stage 2 left enabled. Would this be better? Is there any other way to address a humidity problem (besides a dehumidifier) and hard airflow apart from what I've laid out? We have the typical 7 day programmable honey well tstats and set point is typically 69-70F and a HZ432 controller
You gave us the model of your gas furnace. Can you post your geo heat pump model? Cooling fan speed taps will not work on your furnace blower control unless it gets an "O" signal from the thermostat. Then try ramping profile "D" for better dehumidification. It will slowly ramp the fan up to full setting after 8 minutes and drop the fan down quickly when the compressor shuts off. Do not use continuous or intermittent fan settings. This will only reevaporate the moisture on a wet coil.
A couple more points. The HW HZ432 panel is in charge of staging and how it stages depends on how it is configured. Staging options are Timer, Tstat and %Zones. I prefer Tstat if there are 3H2C thermostats and configure them according to what the zone may need. %Zones could be used to limit to 1st stage if only one zone is calling. Bypass dampers should not be used on a HP system. It raises the temperature of entering air which reduces efficiency.
With the ECM fan you can adjust fan speeds for cooling and heating using the small rocker switches on the Fan Control Card. Use the table in your owners manual to determine how to make the adjustments. Consider checking the return air heat exchanger for dirt, proper draining of the condensate tray or a dirty Air Filter which could keep the unit from reducing the humidity. If the Air Return HX which is the Evaporator in the Summer, is cold, the humidity should drop out into the condensate tray. If no problems can be found then the short run time is the problem as you mentioned. You can keep the unit in the 1st Stage Cooling or Heating by removing the Y2 wire from the thermostat or where the thermostat wires are terminated in the Unit.
