I had a room addition several years ago and in turn I had my HVAC modified for the addition. Since then it's been totally screwed up. Basically I have a VSAH that's pushing 1800 cfm air flow through a 8 X 16 main truck duct that is 54' long that has 19 6" round ducts off the trunk. In addition there are 3 boxed 90 degree turns in the duct before it even gets to the first take-off duct. My NEW HVAC contractor is working to get the system back to spec. In the last couple of weeks he has resized my return ductwork, (it was undersized also) and will start on the supply side shortly. With the AH running he tried to remove the door from the the furnace blower and the suction inside the AH was so great it wouldn't come off, we had to shut the furnace off to remove the door. He said he has never seen one with that much suction before. Is this a sign that the return air ductwork is still too small? What else could be causing this?
Also it seems, according to the contractor, that my heat pump is oversized. What is happening is that the air gets too cold and kicks out the heat pump on AC. So the heat pump runs about 3 minutes then shuts off for 5 minutes when it kicks out. This, with the addition of undersized ductwork, is preventing the house from cooling off. He disconnected the thermostat probe so that it does not read the air temperature and does not kick out the heat pump. He says he never installs the probes in his system and it's not needed. Will this cause a problem?
After getting ripped off so bad by my first HVAC guy I'm kind of leary about this guy now.