Variable Speed? Inside or Outside Unit

[czechkate]

We are renovating the upstairs portion of our house. It was previously an unfinished attic and we anticiapte the installation of a separate split system heat pump. The current AC and Furnace only services downstairs and is 2 years old. We have contacted 2-3 companies in our area (got names from websites of Trane, Lennox, and Carrier).

We got several quotes and are confused. They spoke about and indicate variable speed units to remove moisture and cut down on noise (which we want). But when we looked at product website they talk about variable speed compressor and variable speed fans. Before we go back and talk to them, we would like to be better informed as to exactly what we are getting and what we need/want. Also, one of the salesman said that we did not need a "Manual J" (whatever that is) calculation because our renovation is so small (600 sq. ft.) we will be looking at a very small unit. The other two did not mention "Manual J".

Sorry for the novel and thanks in advance for your replies.

[dash]

Variable speed is for the indoor section ,the outdoor may have VS fan ,likely not the compressor.


Manual J needs to be done,try HVAC-Calc on this site and do it your self,then a Man. d to deign the ducts.

It's likely a 1.5 ton ,but you never know.


VS is the best for controling humidity,great controls like Carrier Infinity really do a good job.If another brand ask for dehumidifing control.



[Edited by dash on 06-03-2005 at 04:15 PM]

[eric fillion]

ok so dont pay for variable speed furnace and dont pay for what they called variable speed heatpump in real is 2 stage heat pump. and i thing i'm not sure 2 stge heat pump start at 3 and 5 tonne cooling so to big for 600 sg feet .the less capacity you will have whit a central one is 1.5 tonne that is good for 1000 sq feet,maybe to powerful, so if it was for mei go for amini split heat pump.

[tecman]

I put a zone in a 500 sq ft last year. Wanted to find a 1 ton split heat pump, but they are rare indeed. I saw Trane had one, but I couldn't get one easily. I thought of a mini split, but the addition had 3 rooms (main area, bath and large closet), so the mini was not a real good choice. I ended up putting a 1.5 ton Goodman in. In both heating and cooling the over capacity has not been an issue. Does not seem to short cycle in either season, and dehumidification as expected. PSC at low setting and 2 more registers than needed to keep the velocities down.

paul