Incorrect settings on AHU during setup cause problems with charge?

[roland764]

I recently had a new system installed, a 2.5 ton Trane XL15i Heat Pump with a TAM7A0C36H31SAA AHU. The installers had left all the dip switches on the AHU in the default positions. The default switch setting for the ODU size was set to 3 tons and by default the ahu’s “comfort-r” or enhanced fan ramping profile was turned off. The switch settings have since been corrected as well as correcting a loose suction line temperature sensor for the electronic TXV in the AHU. Before the switch settings were corrected the return sounded like a jet taking off since it was trying to pull 3 tons of air through a 2.5 ton return. The charge was not rechecked because the outside temperature has been below 55F. Do I need to be worried that the charge could be significantly off due to the original problems?

The one time I have been able to run the system in a/c mode the outside temperature was about 60F and with an inside temperature of about 70F I was getting a supply temperature of 44F. These are pretty low heat load/low ambient conditions, but should I be worried that the temperature split is so large at about 26 degrees F. My main concern would be that the system could be overcharged and could liquid slug the compressor. I do have a 10 year parts and labor warranty, so maybe I should relax and not worry so much about it.

I’ve been reading HVAC-TALK for years & used to do a little work for a HVAC company but I realize this probably gives me just enough information to be dangerous.

Thanks for your thoughts on this!

[Shophound]

It's best to have a warm day outdoors (in the 70's or higher) and a good heat load inside the house before attempting to check/adjust charge. Sure, some techs can simulate it by artifically raising head pressure, but even so they're often working against a house with a low heat load.

[catmanacman]

trane has a performance chart inside the outdoor unit that you can use to verify if you are close in heat mode, this along with weighing in the charge you should be ok until spring whenthey can check the sub cool