I am a building owner. I have several rooftop package units and one of them is past it's design life. I have decided to replace it, rather than continue to bandaid it. This is a 2 stage heat and 2 stage cool application, side discharge, on rails. The application is on Long Island (northeast zone temps).

The existing unit is a York model #D1SS180G26517FDB. I am under the impression this is a 15 ton unit, but I can't find any details at all. York does not give access to older manuals and documentation that I can get to.

The space it handles is 5000 sf, less about 500 sf of hallway covered by another 5 ton unit which covers all hallways. Excluding non-ac areas like closets and such, I figure the net area is 4,250 and that is open and intermingles with force air from another unit doing 5000 sf, so a portion of the load is shared. This space is however, all under the flat roof (top floor).

This being the case, I have been told (and it makes sense), that a modern, high-efficiency 10 ton unit will suffice. Based upon what I've read here, the smaller ac rating may result in a longer runtime on high demand days, but that will do a better job of dehumidification due to more airtime over the coil. As far as heat goes, there is a perimeter hydronic loop in the area, so btu output on a 10 ton will be plenty.

Now, to replace this unit, a Coleman model #RKNB120CM has been proposed.

I know that York makes the unit for Coleman, but to be frank, I can't find any information on this model # either. This is supposed to be a high-efficiency, 2 stage heat - 2 stage cool, with an economizer.

So, the questions I'm throwing out there are:

1. Does anyone have any info on either of these units (old and/or new)?
2. Does anyone have experience good or bad with the branded Coleman units?
3. Does sizing sound ok?
4. Any thoughts or recommendations on equipment, brands, etc for this application?

Thanks in advance for any guidance!