I would like to have suggestions as to what to ask of the HVAC contractor at this point.
2 story home 3,000 sqft, 1,800 downstairs, 1,200 upstairs
Trane XL14i heat pumps, 2.5 tons one unit per floor, 9 vents per floor (returns in bedrooms and hall upstairs, single return in family room downstairs)
85 year old home, remoddled, western exposure back half gutted, new windows, insullated, sheathed 1/2" plywood, vapor barier. Eastern exposure (shaded by large oak tree) blow in insullation in walls.
Complete new HVAC installation, nothing reused from old systems.
As briefly as possible: Neither unit is able to cool adequately. Downstairs unit runs on max speed all day and is best able to achieve 77 degrees, around 2 PM unit begins to lose ground and can only hold 80 degrees until around 8 PM and then can come back down to 77. Similar upstairs but because of radiant attic heat takes until 10 pm to come back down.
A number of problems, primarily with the downstairs unit, have been resolved and both now have an 18 degree split and proper pressure at the unit. All these visits and tuning have netted one degree improvement in the downstairs possible temperature 77 verus 78.
Here are the actions taken to date (please excuse the incorrect terminology)
Replaced thermostats (honeywell 8000 series)
Increased fan speed to 450 cfm
Replaced heat exchanger in the downstairs unit
Replaced control valve (the one attached to the exchanger)
Moved the sensor on the valve from 6 o'clock to 2 o'clock position
Reduced fan speed to 400 cfm
patched two leaks in the duct work coming from the unit in to the crawlspace.
The last technican is their most skilled and he's taken this as far as he can, he said they are operating as effiently as possible and it is the combination of the heat load and leaks that some from it being an older house that is causing it not to be able to keep up.
Perhaps true but not the final resolution. What should I tell the contractor and HVAC sub next?