So we built a new 3300sf home in Houston TX, read tons on Energy Vanguard and HVAC-Talk and tried to do things right: Put the AC equipment in a mechanical room in, put all the ducts in conditioned space and hired a third party HVAC designer to do the Manual J+S+D. He came up with 2 tons AC (105 % per Manual S - with 59TP6040) downstairs and 1.5 tons HP upstairs (125% per Manual S - with FV4C24), using the Houston TX design of 96 outdoor and 75 indoor.
We have ecobee thermostats and have them programmed for 78 away and 75 home.
The issues since we moved in 4 days ago (outdoor temps have been at design or even 1-2 degrees higher):
- When we come home at around 4:30 and the ecobee set point changes from 78 to 75 both upstairs and downstairs are unable to lower the temp for a while. Upstairs will reach the set point by about 8pm whereas downstairs makes it to 77 within an hour but then takes until 9pm to get to 76 and even until midnight to reach 75. This is almost without any internal gains, only two people, all lights off, no cooking, etc.
- Measured with a laser thermometer, the supply register temperature downstairs closest to the AHU is around 58 degrees but then a bit further away in the same room goes to 65 degrees and the master bedroom which is furthest away is even 70 degrees. There is a slight change in room temperature in those further away rooms but surprisingly not a lot (maybe 1-1.5 degrees max) since we have all the doors open. The humidity is between 48 % and 55 % throughout the day everywhere. In comparison, upstairs the air out of all supply registers is between 58 (closest) and 64 (furthest).
- I noticed that there is strong air blowing out of the condensate drain pipes (they have an open standpipe T) for the downstairs unit. The upstairs unit has the same but there is very little air that comes out of the FV4C air handler.
- The front of the coil door of the downstairs AHU is leaking quite a bit of cold air as well.
- The HVAC installers didn't modify the dip switches on the 59TP6 VS furnace per the designer's instructions. The unit was incredibly loud when I first moved in which made me check the switches. I turned the unit off and set the right switches myself (per the Manual this reduced the airflow from 1065 cfm at 0.5 WIC to 800 cfm at 0.5 WIC.
The builder sent somebody from the HVAC company out (two young guys, didn't leave a savvy impression ...) and they checked the pressure out at the compressor and said it was fine. Then they measured the temperature right at the AHU and said the return was 77 and supply was 56 which was perfect and that the system was running at it's best. I was shocked that they just rammed the probe straight into the flex duct instead of having an opening in the plenum. They didn't even tape over it afterwards. Doesn't that leave a duct leak?? I asked them about the static pressure between return and supply since per the Manual D this was supposed to be 0.5 and that if it was different the air might flow faster or slower than the 800cfm design but they said they don't measure static pressure!?! They told me to talk to their boss if I really wanted the extra measurements or items addressed.
Sorry for this long background, my main questions are what I can expect an HVAC installer to do without being unreasonable?
1) Should I not expect a system to recover from a set back during design conditions? (meaning I should not go from 78 to 75 at 4:30 in the hottest days of the summer)?
2) Is the 70F air coming out of the "further away" supplies downstairs a duct system issue or is this normal for longer duct runs and nothing to worry about since the temperature downstairs with all doors open balances out rather well?
3) Should I insist on a static pressure measurement to confirm it is WIC 0.5 per the Manual D design?
4) Should I insist that they seal around the coil to prevent the air leaks?
5) Is the strong airflow out of the open standpipe normal?
We have ecobee thermostats and have them programmed for 78 away and 75 home.
The issues since we moved in 4 days ago (outdoor temps have been at design or even 1-2 degrees higher):
- When we come home at around 4:30 and the ecobee set point changes from 78 to 75 both upstairs and downstairs are unable to lower the temp for a while. Upstairs will reach the set point by about 8pm whereas downstairs makes it to 77 within an hour but then takes until 9pm to get to 76 and even until midnight to reach 75. This is almost without any internal gains, only two people, all lights off, no cooking, etc.
- Measured with a laser thermometer, the supply register temperature downstairs closest to the AHU is around 58 degrees but then a bit further away in the same room goes to 65 degrees and the master bedroom which is furthest away is even 70 degrees. There is a slight change in room temperature in those further away rooms but surprisingly not a lot (maybe 1-1.5 degrees max) since we have all the doors open. The humidity is between 48 % and 55 % throughout the day everywhere. In comparison, upstairs the air out of all supply registers is between 58 (closest) and 64 (furthest).
- I noticed that there is strong air blowing out of the condensate drain pipes (they have an open standpipe T) for the downstairs unit. The upstairs unit has the same but there is very little air that comes out of the FV4C air handler.
- The front of the coil door of the downstairs AHU is leaking quite a bit of cold air as well.
- The HVAC installers didn't modify the dip switches on the 59TP6 VS furnace per the designer's instructions. The unit was incredibly loud when I first moved in which made me check the switches. I turned the unit off and set the right switches myself (per the Manual this reduced the airflow from 1065 cfm at 0.5 WIC to 800 cfm at 0.5 WIC.
The builder sent somebody from the HVAC company out (two young guys, didn't leave a savvy impression ...) and they checked the pressure out at the compressor and said it was fine. Then they measured the temperature right at the AHU and said the return was 77 and supply was 56 which was perfect and that the system was running at it's best. I was shocked that they just rammed the probe straight into the flex duct instead of having an opening in the plenum. They didn't even tape over it afterwards. Doesn't that leave a duct leak?? I asked them about the static pressure between return and supply since per the Manual D this was supposed to be 0.5 and that if it was different the air might flow faster or slower than the 800cfm design but they said they don't measure static pressure!?! They told me to talk to their boss if I really wanted the extra measurements or items addressed.
Sorry for this long background, my main questions are what I can expect an HVAC installer to do without being unreasonable?
1) Should I not expect a system to recover from a set back during design conditions? (meaning I should not go from 78 to 75 at 4:30 in the hottest days of the summer)?
2) Is the 70F air coming out of the "further away" supplies downstairs a duct system issue or is this normal for longer duct runs and nothing to worry about since the temperature downstairs with all doors open balances out rather well?
3) Should I insist on a static pressure measurement to confirm it is WIC 0.5 per the Manual D design?
4) Should I insist that they seal around the coil to prevent the air leaks?
5) Is the strong airflow out of the open standpipe normal?
