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View Full Version : Your help with this system and quote please



chambery1
09-23-2009, 08:14 PM
Heat calculation says 44k btuh heat gain, with 38k of that sensible and 59k btuh heat loss. Central Arkansas single story, 2500 sq.ft.

After half a dozen bids, am thinking of going this way.

Carrier
Comfort series heat pump 25HCB648A30 condensor
CSPH6012A e coil
Infinity series 58CVA110-20 furnace
Thermidistat Edge tstat
10 yr warranty all parts
1 yr labor warranty from installers, reputable company for 35 years.
Qualifies for the Fed tax credit. (Cert # 3494530)

Increase one R/A duct from 12" to 16" round and double the filter grill are on that return. All the contractors have said my duct system is good for 4 tons, except the R/A is borderline for 3.5 ton, much less 4 ton.

Furnace, when in use, should run most of its time in 1st stage. Winter utility bills are 250% higher than summer bills, so heating is my biggest cost. I have a pretty tight envelope with good insulation R factors and excellent windows and am working on improving that.

Quoted price after factory rebates and before Fed tax credit was very competitive with the other Carrier dealer whom I had less confidence in.

These guys do good installation work based on friends and references.

Does this sound like the right system at a fair price?

Your opinions please!!

beenthere
09-23-2009, 08:29 PM
I'd ask them if they can get a smaller furnace that can handle a 4 ton A/C.

chambery1
09-23-2009, 08:35 PM
No smaller furnaces qualify for the tax credit except single stage, with ECM blowers. In first stage heating with VS blower, would this furnace be more efficient than a 90k in single stage?

Thanks

beenthere
09-23-2009, 08:43 PM
Not that you'll notice.

jerryd_2008
09-23-2009, 09:04 PM
... Central Arkansas single story, 2500 sq.ft.

Furnace, when in use, should run most of its time in 1st stage. Winter utility bills are 250% higher than summer bills, so heating is my biggest cost. I have a pretty tight envelope with good insulation R factors and excellent windows and am working on improving that.

...

Your opinions please!!

Wow! Find that hard to believe. Winter in NW Arkansas is about 1.5-2 months, so heating seems to be minimal versus cooling. And you should be warmer than us. Are you looking at TOTAL heating versus TOTAL cooling cost? Did contractors do a Manual J calculation?

Although we set cooling in the high 70's and heating at about 69-70, our TOTAL energy bills were only $1500-1600 per year on a 3700 sqft house with 4 tons AC and 88,000 BTU 80% furnace. Hoping for a lessor amount on a York DFHP with a 2 stage 4 ton HP and 80% 100,000 BTU VS modulating furnace.

IMO going to larger seems like the wrong direction with a more efficient system.

chambery1
09-23-2009, 09:18 PM
Wow! Find that hard to believe. Winter in NW Arkansas is about 1.5-2 months, so heating seems to be minimal versus cooling. And you should be warmer than us. Are you looking at TOTAL heating versus TOTAL cooling cost? Did contractors do a Manual J calculation?

Although we set cooling in the high 70's and heating at about 69-70, our TOTAL energy bills were only $1500-1600 per year on a 3700 sqft house with 4 tons AC and 88,000 BTU 80% furnace. Hoping for a lessor amount on a York DFHP with a 2 stage 4 ton HP and 80% 100,000 BTU VS modulating furnace.

IMO going to larger seems like the wrong direction with a more efficient system.

WOW, you have a hell of a system Yank!! I'd be proud of that sucker too!

chambery1
09-24-2009, 12:58 AM
Not that you'll notice.

Would my pocketbook notice?

dan sw fl
09-24-2009, 05:03 AM
Heat calculation says
44k btuh heat gain, with 38k of that sensible
and 59k btuh heat loss. Central Arkansas single story, 2500 sq.ft.

Carrier Comfort series heat pump 25HCB648A30 condensor
CSPH6012A e coil Infinity series 58CVA110-20 furnace

Increase one R/A duct from 12" to 16" round and double the filter grill are on that return. All the contractors have said my duct system is good for 4 tons, except the R/A is borderline for 3.5 ton, much less 4 ton.

Furnace, when in use, should run most of its time in 1st stage.

Winter utility bills are 250% higher than summer bills,
so heating is my biggest cost.

I have a pretty tight envelope with good insulation R factors and excellent windows and am working on improving that.

These guys do good installation work based on friends and references.

Does this sound like the right system at a fair price?


Check of the calculation could be performed based on review of existing utility bills. USAGE needs to reviewed along with rates.

Stating the % increase of Winter versus Summer bills does not provide USEFUL information. I.E. One might assume from that statement that the summer bills for COOLING [$40 ] as derived from the overall electric bill of $80 and peak HEATING [ $150 ] bill might be $200.

It makes one wonder how poorly the furnace may actually be operating.

OR the electric rates are relatively inexpensive in comparison to the gas or oil rates used for heating.

beenthere
09-24-2009, 06:03 AM
Would my pocketbook notice?
If your a penny pincher.

A mod or staged furnace doesn't save any money by being in lower firing rates. Just provides more comfort.

Remember, if the single stage is 6% less efficient. That means if the CVA would use $1000.00 in a heating season. The single stage if its 89% efficient, would use 60 dollars more for the year at most.

But, the CVA may not be 6% more efficient in low fire. It could be the same as the CVA.
The CVA is a comfort unit.

chambery1
09-24-2009, 04:00 PM
Back to the original questions, what do you think about the system? Specifically, the heat pump.

Keep in mind that meeting the Fed tax credit requirements puts a limit on which furnaces are available.

If the heat pump performs as rated, then the use of the furnace will be limited as will be the CCF's of natural gas consumed and paid for. When I start applying savings rates due to efficiencies of higher rated furnaces, I can't get the savings to justify the additional initial cost of the higher rated units.

What are your opinions on this Carrier heat pump?

Thanks

beenthere
09-24-2009, 04:10 PM
The heat pump is fine.
I didn't look up its performance ratings.

Carrier makes fine equipment.

Did they do a load calc. Do you know at what outdoor temp the system has to switch to the furnace.

40, 35???

chambery1
09-24-2009, 04:47 PM
Yes, their load calc numbers are shown in the initial post. I also ran a load calc using HVAC-Calc and my numbers were just less than theirs. I know I'm oversizing the furnace but it seems the best way to go to get the tax credit $$ versus initial costs and operating costs.

Using Carrier's balance point worksheet, the HP should operate 1st stage down to 42, 2nd stage down to 34, then switch to furnace.

beenthere
09-24-2009, 04:56 PM
Find out how many hours you spend at or below 34. And then, when and if first when the furnace will go to second stage.

chambery1
09-24-2009, 06:59 PM
108 HDD using 34 degrees, 90 HDD at 33 degrees. All HDDs based on 5 year averages from degreedays.net.

Carrier furnace is supposedly 60% 1st stage, so 110K at 80% eff. is 88k at 60% 1st stage is 53k. Per HVAC-Calc 53k is sufficient down to 15 degrees. HDDs below 15 are zero per degreedays.net. HVAC-Calc uses 10 degrees as default outside design temp. for my city. Don't know if I'm doing the math right.

2 questions, 1) Do these numbers mean the furnace should rarely kick into high stage? 2) What does all this mean to you? because I sure don't know. Which raises a third question I suppose, what questions am I not asking!

Thanks again

beenthere
09-24-2009, 07:06 PM
If HVAC calc used 10, and you never really have temps that go below 15.
Your furnace will almost never go into second stage. Except for recovery if you use set back.

I'd ask them to double check, that there isn't any other furnace that will get you the tax credit(might not be).

First stage isn't always as efficient as second stage. When it comes to furnaces.

chambery1
09-24-2009, 10:12 PM
Under what circumstances might 1st stage be as efficient as 2nd stage?

And to turn that around, under what circumstances might 2nd stage be more efficient than 1st stage?

Where would one go to get this type of information? http://www-library.lbl.gov/docs/LBNL/598/65/PDF/LBNL-59865.pdf

Conclusion: Based on the 2006 ASHRAE test procedure, which appears to provide a more accurate
method for calculating the energy consumption of two-stage furnaces, the results indicate that
two-stage technology by itself does not save energy. However, the combination of two-stage
furnaces with BPM motors (BPM motors are also known as Electronically Commutated Motors (ECM) which is registered trademark
of General Electric) provides electricity savings and overall financial benefits to the
consumers.

I think I'll stay with the VS two-stage.

beenthere
09-24-2009, 10:16 PM
First stage is seldom as efficient as second stage. Its just a few percent lower then second.

It was printed in a study. Don't remember what it was called though.

chambery1
09-25-2009, 12:25 AM
First stage is seldom as efficient as second stage. Its just a few percent lower then second.

It was printed in a study. Don't remember what it was called though.

You don't agree with the above referenced study?

I am still searching the web for info but not having much luck. That study indicated that 2 stage with VS saved $ due to lower electrical costs for blower, with virtually no difference between fuel cost for single stage versus 2 stage heat. Still looking for the answer.

beenthere
09-25-2009, 05:26 AM
The blower operating cost was less. But was on proper duct system, not an under sized one with high static pressure. Is your duct system sized to have .5" total static at max firing rate.

Also, reread that report. One study has a 2 stage VS using 3% more fuel.

Your house is not a lab. So the furnace isn't working under Ideal conditions.