Terminology for HVAC system

[149256]

I have an older HVAC unit and I just want to know the correct terminology for what type of system it is. I have a single gas furnace air handler that feeds 2 separated slab evaporator coils. There are 2 duct systems separate from each other and each duct system is connected to one evaporator coil. Each evaporator coils has its own exterior compressor. I think this is usually found in commercial systems, but mine is in my home. Is this just a dual system?

I've been keeping it going for years, but I think the secondary heat exchanger is going or has gone bad and looking for a new system that can fit in current space.

Thanks

 

[Fitter30]

Outside units are condensers. That temp star is gas heat? But don't see the flue! House has two separate zones, one or two thermostats? How does the heat work by either thermostat or just one?

 

[Sponsor]

 

[149256]

Outside units are condensers. That temp star is gas heat? But don't see the flue! House has two separate zones, one or two thermostats? How does the heat work by either thermostat or just one?

Thanks. Yes I do realize that the outside units are condensers. The system does the flue it's just not visible. It's 2 inch PVC pipe, its a condensing furnace. And yes it's gas heat also there are two thermostats that control each of the ducting separately for gas heat and cooling they also have dampers on the supply and return on each of the ducts. Situation I'm running into is finding a similar set up these days. The only ones I can find are commercial units but they run on three phase power which I do not have. I'm just trying to keep the cost down with a replacement model. Trying not to buy two separate air handler/furnace units. Thanks again.

 

[Dana]

If you're replacing the whole thing you're probably going to be better off with a right-sized heat pump than replacing it with another oversized fossil-burner + oversized AC coil. The thing looks huge (perhaps ridiculously oversized) for a residential application.

With last winter's gas bills it's possible to reasonably estimate the 99% heat load using the existing furnace as the measuring instrument. A professional engineer's or RESNET rater's Manual-J calculation would include both heating and cooling loads. Do NOT let the average HVAC contractor run the numbers- they tend to have nervous thumbs on the scale pushing you toward oversizing. Even though the upcharge in higher capacity equipment isn't enormous, oversizing takes a toll on both comfort and efficiency. (Most people in the US have never lived with right-sized equipment, and may not know what they're missing.)

Any replacement equipment's capacity should be no more than 1.4x the design load, but if a heat pump it should be as close as possible to (even slightly less than) the design load, and use resistanct heat strip to cover the shortfall during the 1% of hours in a year that the load is greater than design condition. With a heat pump you don't want to use deep overnight setbacks, since that would engage the much lower efficiency heat strip during recovery ramps. There are many heat pumps with rated capacities even in negative doubld-digits F now- these aren't like your grandma's R12 single stage tepid-air heat pump from 1980.

 

[Fitter30]

Is there multiple zone dampers or just two for controlling the air either from one side or the other. Explain how you control the system.