I've been getting quotes for adding a heat pump to supplement my existing natural gas furnace.
The trane guy says you can't do a dual stage compressor on dual fuel system since my existing blower is not variable speed.
That seems to make sense to me, however the Lennox guy quoted me single and dual stage compressors without mentioning this as an issue.
With a standard blower, you won't get near the SEER the units are capable of. Also the airflow never will be right. It may be possible to jury-rig a relay to play with the blower speed for the 2 outputs of the outdoor unit but that's just hit or miss at best.
Baldie has a point,but it is possible,the Carrier Thermidistat,will control a standard fan motor with a two speed compressor or for a dehumidification call.
They are stuck with using the fan speeds you have available,and the static of you duct system needs to be tested in advance to predict what speeds to use and the resulting cfms.
It will not deliver the "exact" cfms ,as a variable speed indoor fan would.I'm not saying it's a good way to go ,but it can be done ,assuming the duct system was designed properly to start with.
you wont have any humidity removal in low speed, just buy the whole system or buy a single speed high seer system.
you hardly ever get the seer rating on the equipment and without variable speed it will be even lower.
so if that system says it will get 18 seer youl probalby only get 14 or 15 without varible speed furnace it may even be 13 or 14 actual seer.