Heat Strips

[lksmith]

There was a previous thread (which I can no longer find) where a homeowner (from GA) was talking about having two dual fuel systems installed--one for his upstairs and one for his downstairs. He lived somewhere in GA. One of the "responders" suggested that in lieu of putting in a furnace upstairs he just use supplemental electric heat because of the added heat that would be available from the downstairs furnace.

Well, that seemed like a reasonable idea to me since I live in Atlanta and am thinking about replacing my two systems with dual fuel systems. Seems like there is money to be saved instead of installing a 40K BTU (as suggested by a Trane sales guy) furnace for the upstairs. The Trane sales guy concurred with this idea.

Had a Carrier sales guy over this morning working on a bid and I ran the idea by him. He was dead against it. He said that I currently had only a 15A circuit to run my furnace and that I would need 60A to provide sufficient power for the heat strips. (I see two 20A breakers tied together in my circuit breaker panel for each furnace.) He seemed to think the cost of adding additional electrical capacity would far out way the cost of a new furnace. I think he said the cost of an air handler with electric strips and a variable speed blower would be roughly the same as a furnace (Carrier 70 K BTU he was suggesting) with a variable speed blower.

What do you all think. I'm not sold on any particular way to go. I would obviously like to get the best bang for the buck. Thanks.

Larry Smith

[Wild Leg]

If you currently have a gas furnace, you should not have two breakers tied together serving it.
Those breakers either go to something else, or they are misapplied.

Yes, you likely would have to upgrade the service to run heat strips.
That does come into play, when doing a cost analysis.


Get another opinion.

[lksmith]

Oops...

The two 20's are for the outside units. The furnace breakers are 15 A breakers. Time for stronger glasses.

Larry Smith

[tigerdunes]

lksmith

My suggestion is to go back to your Trane dealer and ask them the cost of the the appropriate size high eff heat pump paired with var speed blower along with the necessary size of heat strip. Then ask him what size breaker you would require for the starting amp draw and the operation of this unit with aux strip heat. Then ask him if your breaker panel has an open slot to handle the capacity required. Heating with a heat pump in Georgia with your reasonable electric rates is your best choice.

My opinion.

[lksmith]

Tigerdunes,

Thanks for your input. I will follow-up with the Trane dealer with those questions. I did want to ask you about you last sentence,

"Heating with a heat pump in Georgia with your reasonable electric rates is your best choice."

Are you suggesting the use of supplemental heat strips or the gas furnace as a back-up to the heat pump?

Larry Smith

[docholiday]

You will likely not be using the aux heat very often anyway. The only costs you can compare are for those times when the aux heat is required and in those cases, the gas will surely cost less. The heat pump part which will do the lions share will cost less to operate than the other two options.

You may also look at what will heat your home in the event of a HP failure. The gas, again will cost less. Given the cost of copper (wiring) and the additional electrical work needed, I would suggest staying with the set up you currently have.

[tigerdunes]

lksmith

Forget the gas furnace for the 2nd floor and purchase a high eff heat pump(with heat strips)paired with var speed air handler.

As far as the main floor, you have 2 choices that make sense-dual fuel(and I would only go with an 80% AFUE var speed furnace)or another system like the upstairs floor.

Nat Gas is no longer a value fuel for winter heating due to supply/demand issues, energy speculators, and possible market manipulation by the the integrated energy companies all the way to the homeowner. I would expect electric rates to be more stable over the next 10 yrs as opposed to nat gas rates, particularly those electric companies with a large nuclear footprint.

Make certain new HVAC equipment is sized correctly. Do not undersize 2nd floor due to those terrible Hotlanta summers. Insist that your dealer perform a thorough inspection to your ductwork system as far as size, supply/return balance, insulation properties, leakages, and address any hot/cold airflow issues that are ductwork related.

My opinion.

[iheatncoolinnc]

Upper level - Why not use the small gas furnace with variable speed blower with heat pump. The gas furnace will probably hardly ever run. The heat pump will do most of the heating for the upper level. The electrical circuit is already upstairs for gas furnace. The gas line is already there. You are not going to get the all electric rate with gas heating downstairs. Lower level I would do the same except I would think about a 90%+ gas furnace for the lower level. A lot of the older houses have to have flue work for the 80% gas furnaces. Look at 80% and 90% option for lower. In atlanta it probably would not justify the 90% if it cost a lot extra. I would strongly suggest the use of heat pumps on both levels with gas furnace back up.

[lksmith]

Well, thank you all for your responses. I don't think we "nailed down" the options but I can now at least get the HVAC guys to price out both options. I'm all but certain that I want the dual fuel option downstairs, it's only the upstairs that is sort of an unknown. I must admit that in the event of a HP failure, it would still be nice to have the furnace as a back-up. I'll see how it all prices out, with the addtional electrical work to be done for the heat strips, and go from there. Thank you all again.

Larry Smith

[berg2666]

OK Lets start over.

From what I have read you have the following. Please correct me if I am wrong.

Downstairs, Gas Furnace system and you want to replace with a dual fuel system.

Upstairs , Gas Furnace system and you want to replace with a heat pump and electric heat backup system, which will be contained all in the air handler.


My Opinion
You have a 120 volt gas furnace system upstairs. If you want a heat strip system you will nned 60 amps of 240 volt.
Which will require bigger wring from the breaker panel, provided you have the capacity in the panel for it, and if you have room in the current conduit for it. I think the price of rewiring will be more then a 40 btuh furnace.
Copper is pretty expensive.

[Edited by berg2666 on 09-01-2006 at 09:29 AM]

[lksmith]

Hi berg2666,

Presently in the attic I have 2 gas furnaces, one for upstairs and one for downstairs. I am definitely going to go dual fuel for the larger downstairs system. I was contemplating swapping out the furnace for the upstairs with an air handler with heat strips. I do have room in my electrical panel for double pole circuit breakers but I'm sure additional power will need to be run from the garage (where the panel is) to the attic (where the air handler would be).

Let me say that "contemplating" is the key word here. It appears from most of those responding to this thread that bringing 240V up to the attic is not going to be easy or cheap so I'm not sure it's the way to go. This whole idea came to me from a previous thread in this forum and a Trane dealer who said an air handler was less expensive than a furnace. At that point we didn't (and I didn't consider) what the additional cost of running new power from my panel to the attic.

Larry Smith

[iheatncoolinnc]

With a manual j load calculation of your upper and lower level, the contractor should be able to determine the balance point of the heat pump. This would be the point at which the heat pump would not satisfactorily heat your home and the back up heat would have to heat your home. I think in Atlanta you will find that the heat pump is going to heat your home most of the time. The operating cost of the backup heat is going to be minimal. I do not think it will matter which you use, electric or gas. Have the windows, walls etc.. been measured by any of the contractors looking at installating heating and cooling in your home? If they have not done proper measurements then they cannot determine how much heating or cooling you need or your balance point. Has the ductwork been looked at and measured for proper air delivery for your new system? Have optional fresh air intake or air filtration been offered for the new system? Digital electronic thermostat or programmable thermostat options are available also.

[tigerdunes]

lksmith

Also add a whole house air cleaner cabinet for your consideration.

You will get a little better operating eff with a var speed air handler paired with a heat pump as opposed to a var speed furnace.

A backup gas furnace for downstairs will allow you enough heating in the winter to survive an upstairs HP breakdown until this system can be repaired. A dual fuel system for upstairs is simply not necessary and is overkill.

My opinion.

[berg2666]

Larry
I hope that you were given educated opinions from us on this forum to help you make the best decision possible.

Erik

Berg Inc.
Shreveport, La

[lksmith]

Hi Erik,

Thanks to you and all the other pros on this forum for bringing up all the pros and cons on this furnace vs. gas furnace issue. This was not as simple as the variable speed vs. multispeed blower question I had posed earlier. I think the best thing for me to do is to bring up all the questions that have been raised on this thread and let the contractors chew on which system they think will provide the best bang for the buck, both dollar wise and comfort and efficiency wise.

One last thought for those who have commented....Let's hypothetically say I already had 240V/60A of power in my attic (which I don't) and still had all the existing furnace requirements (flues, gas lines, whatelse). How would that change the heat strip vs. dual fuel furnace question? In other words, let's take the money end of installing electrical wire out of the equation and talk about just system efficiency, comfort, system costs for about 800 - 1000 sq. ft. of living space upstairs. (Sorry, no load calcs done yet. Will be before final system selection.)

Larry Smith

[hivacer]

If you already had the power there I would go with the heat strips over the gas furnace. Probably your upfront cost will be less with an electric furnace over a gas furnace becasue no Flue, no gas line etc. With the electric furnace you have only electrical connections, and of course duct connections and piping and drain for your heat pump.

As for efficiency it depends on your rates for gas compared to electric, but It seems to me that electric is more stable than natural gas, and gas rates have been skyrocketing lately, I would be more comfortable with electric, and electric strips are always 100% efficient, and your heat pump could be 300% efficient if you look at it in a certain perspective relative to your heat strips.

We can create electricity from coal, water, nuclear, wind etc. etc. etc.... But gas is a dwindling resource and who knows how our supply and demand issues will go.

And as for comfort, I believe either one will be the same, but gas does produce hotter air temps out of the register, but this doesnt really matter. You should consider a humidifier to control indoor humidity with either system.

[taterbugbrown]

A comment about the 60A/240v circuit. That would only apply to a 10kw heatstrip which is usually paired with a 2.5 to 3 ton air handler. Depending on your load calculations, you may only need an 8kw or a 5kw heat strip which do not require such a large circuit. You would be looking at a 40A for an 8kw and a 30A for a 5kw. The smaller circuits also mean smaller wire which would reduce the cost of adding the circuit.

[lksmith]

Thanks for the info...currently there is a 2 ton system system servicing the upstairs. Haven't done the load calcs but I suspect it is more than adequate for that part of the house.

Larry Smith