Setting up Dueal Fuel System for optimum performance

[hamons]

So I am not getting any benefit out of having a 2 stage furnace?

[wyounger]

Originally posted by BaldLoonie
Black, you can't do 2 stages of gas backing a heat pump with the VP. At least the way they have it designed. If you want to do some crazy wiring you might be able to jury rig something. I have an old Robertshaw 9720 and a DPDT relay. Pump is stage 1, gas backup is 2 & 3 though normally I have gas backup shut off via a toggle switch. A White-Rodgers 1F90 with 3 stage heat will do the same. The VP won't.

Looks like Loonie's right- I just checked the VP manual. I hadn't thought about that issue.

Blackadder, it looks like you *could* do (other than using the furnace board to control its own staging):
-configure it for 2H/1C with your second heating stage as low fire, and emergency heat as high fire. About the same effect as a toggle switch, but tidy enough to not annoy the missuz.
-use an outdoor thermostat to control furnace staging...?

It's a shame it's so hard to get a single stage furnace with variable speed (Nordyne or bust?) A two stage furnace in conjunction with dual fuel is kinda redundant, and frequently control systems can't handle all the stages anyway. And just watch out if you're looking at a two stage heat pump and a two stage furnace... not much will handle that. Infinity systems can do it.

Y'know, I just went looking, and apparently the Thermidistat can do four stages? I've never tried it, but it looks to me like they can handle a two stage heat pump with a two stage furnace. In fact they even let you program it to choose whether you want low fire or high fire for defrost tempering. It's not as pretty as a VisionPro, but in some ways I still like its bells and whistles better.

And the regular Carrier dual fuel stat can certainly handle three stages in dual fuel, either with a two speed furnace or a two speed heat pump. I have to say, Carrier's dual fuel stat was way ahead of its time when it was released.

[Edited by wyounger on 10-13-2005 at 02:24 PM]

[wango]

So if I have a HP with a two stage furnace with a VS motor I would be stuck with the HP and firststage heat only.

The VP model I have has 3heat and 2 cool.

Is it the VP that controls the 1st to second stage adjustment or is it the furnace?

[docholiday]

Originally posted by hamons
So I am not getting any benefit out of having a 2 stage furnace?

Yes you are. Not financial but comfort. The full fire is probably not needed. Mines a two stage furnace under a heat pump. Works great.

[inturmoil]

BaldLoonie
Associate

Registered: May 2000
Posts: 13299
Black, you can't do 2 stages of gas backing a heat pump with the VP. At least the way they have it designed. If you want to do some crazy wiring you might be able to jury rig something. I have an old Robertshaw 9720 and a DPDT relay. Pump is stage 1, gas backup is 2 & 3 though normally I have gas backup shut off via a toggle switch. A White-Rodgers 1F90 with 3 stage heat will do the same. The VP won't.


Yes you can. There are at least a couple of ways.
With a trane you could just jump w1-w2 and there would be a 10 min timer for 2nd stage gas heat.
I put in a Trane 16i (two stage) heat pump and did it with a vision pro. Use your imagination.
Jason

[dan sw fl]

Originally posted by hamons
I guess bottom line is I'll have to play with it. Lots of variables to mess with though.

Setback temperatures and balance point.

Right now balance point is set to 30 degrees.

With those VERY LOW electric rate$,
maximize heat pump use.
28'F " seems " just about right.

I didn't realize anyone is as low as $0.04/kW
(except Time-of-Day rates).

[wyounger]

That is really, really low. Is it really 4 cents total in KC? I know these things can be easy to misinterpret... utility rate structures can be absurdly complicated.

I know if you go looking for Georgia Power's winter rate, it looks like 4.something cents per kwh, but if you read the fine print, their is a separate "fuel cost recovery schedule" that adds another 2.6 or so cents per kwh to cover the cost of the fuel for the plants. The four cents covers everything else.

[hamons]

We get a special Heat rate if we use a heat pump.

Standard Rate:

Winter (8mos) = $.0651/kwh
Summer (4mos) = $.0736/kwh

plus monthly service charge of $5.78

One Meter Electric rate

Winter (8mos) = .0430/kwh for the 1000 kwh and .0339 after that

plus monthly service charge of $5.76

Summer = .0736

[wyounger]

Wow, wow, wow.

I wouldn't let the gas company near my house if my electric rates were like that.