Hi, I'm Douglas and I am here to help you resolve problems with your heating and cooling equipment.
A heat pump is a system, not just a couple of random components. This is especially true with the 13 SEER minimums. The indoor coil becomes the condenser
coil in heat. Each manufacturer designes the indoor and outdoor sections as a matching pair. From page 1 of the 13HPD installation instructions: This unit must be installed with a
matching indoor unit and line set as outlined in the Lennox Engineering Handbook.
The UBHC-17J11 is a 10 SEER air handler and will not have the refrigerant capacity to function properly without a huge charge imbalance issue. Not to mention performance, capacity, efficiency and overall reliability goes. I have heard too many techs say... "I do it all the time" well they dont know that sooner or later the customers just call someone who deals with the mess.
That is not to say there is anything wrong with the Ruud air handler, it's just not a consideration with that outdoor unit. Even a new Ruud unit would not work with that air handler.
The right thing here is to replace the indoor air handler with the proper match for the outdoor unit. Unfortunately because the indoor air handler is a 10 SEER, there is no outdoor unit that will match it. Option 2 is fight it. I wish there was a kind way of saying it but you got hacked by a hack.
The matching air handlers from Lennox are spelled out on page 10 of the spec sheets found here. http://www.innovation-group.com.ua/downloads/eh/60/hp/13hpd.pdf
Although some other companies build air handlers to match these by using Lennox design criteria. Allstyle for instance may make a matching air handler for this.