Modulated vs 2 stage

[sealman]

I have a 3000sq ft - 2 story with finished basement- (philadelphia )
looking at a single stage 4ton 14 seer hydrid heat pump with a Modulated gas valve furnace (propane )


Pros and cons Please

[Jim Davis]

I have a 3000sq ft - 2 story with finished basement- (philadelphia )
looking at a single stage 4ton 14 seer hydrid heat pump with a Modulated gas valve furnace (propane )


Pros and cons Please

Better off with 2-stage variable speed(blower) furnace. Has more adjustment capabilities so they don't blow as much cold air. Modulating furnaces have very little field adjustments.

[beenthere]

A mod furnace will give you more heating comfort then a 2 stage will. How much more varies with each house and person. The blower speed can be adjusted for temp rise.

A balance point should be plotted to see where your gas furnace will take over. Depending how low of an outdoor temp the HP is able to run at, a 2 stage may be better, or a mod.

[21degrees]

2 stage compared to mod you will barely feel the difference in comfort. 2 stage has been arround alot lot longer and if ever faced with problem, it will be alot cheaper to repair.

[sealman]

Ok - 2 stage furnace
Now the Heat pump / AC
If we go with a 2 stage first stage will only have enough air flow to cover down stairs and basement ( Path of lease resistance ) and 2nd stage will only come on when the temps are extreme. That leaves the upstaires cold in winter hot in summer.

Does this hold water???

[beenthere]

No, it doesn't work quite like that.

[21degrees]

[QUOTE=sealman;1888808]]

The heating and cooling stages are seperated and have set speeds for levels of demand. are you talking about 2 stage cooling?

[sealman]

2 stage cooling the concern is not enough cooling up stairs


During 1st stage doesn't the blower run at lower speed ( 50% output )

[beenthere]

More like 60 to 80% depending on brand and model.

[beenthere]

2 stage equipment is not a fix for bad duct systems. They can eliminate some duct problems, but they are not a cure all.

[Jim Davis]

Forgot to mention airflow.

With a modulating furnace you can blow cold air out of all the registers or warm air out of just a few. 300cfm in a 1200cfm duct system isn't going to see much air at the farthest point.

[beenthere]

Forgot to mention airflow.

With a modulating furnace you can blow cold air out of all the registers or warm air out of just a few. 300cfm in a 1200cfm duct system isn't going to see much air at the farthest point.

Your some what backwards on that.

You can have more of a problem with low air flow at the closer supplies then the ones furtherest away. The static pressure at the beginning of the duct is low at 40% modulation, so the air can travel past an early supply or 2, and you have more air coming out the ones further away. This is on systems that no one has bothered to balance.

Do a proper balance and there is no problem.
Weather your talking about a 2 stage A/C, or a mod furnace.

[Jim Davis]

Wouldn't that be like saying the foot of throw out of a register increases or reaches the other side of the room faster with lower airflow because there is less static?