dual fuel

[pony express]

i'm getting ready to purchase a new system. carrier 80% v.s. two stage furnace and a 14 seer condenser.
i'm in sacramento, ca. average high 92, average low 45 last year cost per therm averaged close to $1.60. i'm real curiuos about a dual fuel system in my climate.(in the winter if you have a heat pump, you pay about 7 cents per kwh for the first 1000kwh) I asked my contractor about a straight heat pump conversion. he likened it to going from a car to motorcycle to save gas...
what, if any would a dual fuel system save me? (ballpark) i averaged 110 therms per month last winter. on a 28 year old 125,000 btu input furnace.

Thanks for any insight. or any direction to find the answer...

[beenthere]

Have a load calc done to see what size you need.

Then get another contractor. One that understands heat pumps.

[jim baughman]

A straight heat pump conversion with heat strips for backup, just in case, would be fine for your climate. As far as savings go...that is hard to figure since there are so many variables involved....ducts, insulation, cost of fuels, etc. I would hate to try to quote a savings figure to anyone. But the heat pump system has less parts to fail than running both a furnace and a/c systems.

[citywide service]

After the load calc was done I would stick with the heat pump system in your area. I think that nat. gas prices are out of sight now, why pay for a heating form that is going to rise faster than another?

Your electric rates are reasonable, stick with a V/S airhandler, the recommended KW heat strips and go with the heatpump and never look back.

Being as your in Calif. I will say this:

Go with the highest efficiency R410a system you can afford -even if you have to finance some or all of it it will raise the resale value of the house and give you a faster payback and more comfort in the long and short runs. The heatpump on 410 will probably be all you'll ever need with those design temps.

Make sure you address dehumidification with the contractor, and "oh this will handle it" isn't good enough. Make him show you the calc figures. Most have told me that with the electric heat and heatpump humidity isn't a concern in the winter...I don't think I believe that but we will see this winter as this is my first all electric system.

Hope that helps some,

CW.

[tigerdunes]

pony

A high eff heat pump system is really the perfect choice for your climate.

However, you need to have an absolute understanding of California's tiered electric rates which I am told are on extreme side. Just double check this. If electric rates are OK, forget the gas furnace.

I suggest you look at Carrier's Infinity heat pump systems.

Make certain a Manual J heat/cool load calc is performed, get this in writing and review in detail with your dealer.
Also have your ductwork checked as far as size, insulation properties,supply/return balance,leakages, and any hot/cold spots to be addressed due to poor airflow.

IMO

[pony express]

thanks for the replies. it's a two story with most of the duct work between the floors. in cali. to obtain the permit you have to satisfy title 24 and get tested and pass to under 14% ductleakage. it's hard to estimate savings. however with ductwork being equal on the two systems. i was looking for a formula to enter cost per therm/cost per kwh. and the efficiency of the system and get an idea of the difference.

Thanks again for the replies

[pecmsg]

1 kilowatt-hour of electricity = 3,412 Btu
1 cubic foot of natural gas = 1,026 Btu
1 therm of natural gas = 100,000 Btu
1 gallon of propane = 91,000 Btu
1 gallon of gasoline = 124,000 Btu
1 gallon of heating oil = 139,000 Btu
1 gallon of diesel fuel = 139,000 Btu

[tigerdunes]

pony

Here is a fuel comparison calculator. This may help you with your decision making.

Good LucK!

http://www.warmair.com/html/fuel_cost_comparisons.htm

[pony express]

i'm still at it. my carrier guy says hybrids are too new. he thinks i'm crazy for considering even just a heat pump. Is there more air flow on a heat pump compared to a furnace and a 4 ton a/c system?

electricity is 7.9 cents for the first 1000 kwh then it goes to just over 14 cents kwh after that. natural gas 1.70 last winter with usage about 500 therms heating for the winter season. payne furnace built in '78. it's a big dollar item. I want to make the right choice.

Are there any links that will tell me what a 8.0 hspf( i don't have the COP) heat pump uses in electricity(KWH) per btu. or is it more complicated then that...

thanks again for any input.

[docholiday]

I cant get real scientific, but my heating costs are about 40 percent lower with a dual fuel system than my neighbor who has virtually the same gas furnace but no heat pump. It's a real shame your contractor has blinders on.

[icyflame]

[QUOTE]Originally posted by pony express
[B]i'm still at it. my carrier guy says hybrids are too new. he thinks i'm crazy for considering even just a heat pump. Is there more air flow on a heat pump compared to a furnace and a 4 ton a/c system?


Your carrier guy is saying r410a is a new hybrid. He is not in good grace with the Carrier Corp. R410a has been on the market for over five years, may seven or eight years. R410A is being promoted by Carrier in a national multi million dollar ad campain Trying to make the brand name PURON a household word as the present brand name FREON. PURON is here to stay. A Puron Heatpump with the proper sized electric heat package would be a very economical and satisfing system. Don't let them set the LBP at 40 degrees. I run mine down to 20 degrees and feel as though I could drop it another 15 degrees. My backup runs around five percent of the time.

[docholiday]

No, Hybrid is the 2006 buzzword for dual fuel systems. It has nothing to do with what refrigerant is used per sey. And yes, dual fuel systems are not new by any stretch. You may recall the term "Add on Heat Pump"... Thats dual fuel. It just gets a new name every once in a while.

I do agree with not just setting outdoor thermostats at some arbitrary setting. I have found that my heat pump does the work down to 17 degrees. Every home and installation are different, but if the contractor can do a little math, he can figure that balance point.

[icyflame]

:D Thanks for the update! :D

[jayhvac]

http://www.energyright.com/heatpump/dare2compare.htm

here is a link i found that let's you change the energy costs and also look at different heating requirements depending on where you are in the country. This might help you adjust for a lot of factors.

[pony express]

thanks jayhvac. that supports what doc said about him and his neighbor. the carrier guy tells me his mid-level heat pump has eer 0f 11.9 just shy of the 12 min eer to qualify for our local rebate.so i could be looking at paying 20% more for the heat pump.

what's the average life span of a heat pump?

[dan sw fl]

Originally posted by pony express
... more air flow on a heat pump compared to a furnace and a 4 ton a/c system?

Electricity is 7.9 cents for the first 1000 kwh
then it goes to just over 14 cents kwh after that.

Matural gas 1.70 last winter with usage
about 500 therms heating for the winter season.

payne furnace built in '78.

Are there any links that will tell me what a 8.0 hspf
( i don't have the COP) heat pump uses in electricity (KWH) per btu. or is it more complicated then that...



TRANE XL14i
8.7 HSPF
3.5 C.O.P. at 47'F

You need to determine the size of the heat pump
(i.e. 3.0, 3.5 or 4.0 ton) required.

Energy Cost Comparison

Therms used ( Annual) ___ 500
BTUh/ Therm _______ 100,000
BTUH Total ________ 50,000,000
Furnace Efficiency ___ 80%
Effective BTUh Output ___ 40,000,000

C.O.P. for heat pump ___ 3.3

Effective BTUh
for Heat Pump ________ 12,121,212

BTUh/ kWh _________ 3,413
kWh for Heat Pump ( Annual) ___ 3,551

$ / kWh ( < 1,000 KWH) ________ $0.079
Electric Cost for Heat Pump _____ $280.57
Cost for Gas per Therm _____ $1.70
Total Natural Gas Cost _____ $850.00

Savings ________________ $569.43

You also should review your monthly gas and electric usage to determine if you may exceed 1,000 kWh per month.
I suspect your heating usage for a heat pump
may be similar to:

Month _______ kWh
October _ ___ 200
November ___ 400
December ___ 600
January ___ 900
February ___ 800
March __ ___ 500
April __ ___ 200
Total _______ 3,600

You may wish to contact a local mechanical contractor who is familiar with heat pumps and their advantages.

[pony express]

thanks dan, that's helpful info. the contractor is putting together a dual fuel estimate.the carrier "hybrid" hasn't made it here to cali. yet :confused: i'll weigh that against just a straight heat pump. thanks to everyone for taking the time to reply...

[pulaskihvacr]

Originally posted by citywide service
Make sure you address dehumidification with the contractor, and "oh this will handle it" isn't good enough. Make him show you the calc figures. Most have told me that with the electric heat and heatpump humidity isn't a concern in the winter...I don't think I believe that but we will see this winter as this is my first all electric system.

Hope that helps some,

CW.

Indoor RH has nothing to do with the fuel used for heating the air. If you simply raise the dry bulb temp (Heat) the RELATIVE humidity goes down. For all intents and purposes, the amount of actual moisture in the air doesn't change. Humidification should still be considered.

[pony express]

New twist...

We get a lot of fog in the winter. does that effect the efficiency of a heat pump?

[pulaskihvacr]

That's one I would have to give some thought to.. Fog implies that your outdoor conditions are above freezing, so defrost should't be affected (unless your Fog occurs at or below about 40F) Otherwise, except for coil condensation, I don't see it affecting capacity.

[docholiday]

Actually, fog can be a real pain when it occurs in the 30's because your outdoor coil will be below freezing and there is plenty of moisture to freeze to it. Just be sure to use either the shortest defrost intervals or a demand defrost system.