The 60kBTU unit is AUH2B060A9V3VA and costs $1212 before the $600 rebate.

The 40kBTU unit is AUC1B040A9241A and costs $621. The heat loss calculation is $36kBTU.

That 40K you were quoted is their builder unit. Only 1 pipe venting (no sealed combustion). They do make a 40K single stage with ECM motor, but I would not recommend because it uses the X13 motor. The X13 is not variable speed and I have seen reliability issues with it in my area on all equipment brands. Also that model does not hit 97% efficiency, so would only get the $300 rebate and be more expensive than either of the options you mentioned. If you go American Standard, the 60K 2 stage variable speed is the no brainer choice.

I just checked, and unfortunately, all the other brands only get 96% AFUE on their 2 stage variable speed models, so only the American Standard and equivalent Trane will get the $600 rebate. So your 2 best options are:

1. AS 60K 2 stage variable speed. This would be the best value.

2. Pay a bit extra and get a 40K 2 stage variable speed from a different brand. This would be the best comfort option.

That sounds sensible......The only 40kBTU supplied by the gas company is the AS "builders model". I will talk to my contractor about the cost of 40kBTU unit from another manufacturer.

I would rather see you buy the American Standard 60K BTU 2-stage furnace, than an Goodman 40K BTU 2-stage model. There are few choices in 40K sizes and even less for 2-stage.

Assuming the duct work is adequately sized, having 60K BTU will be nice when you are coming out of temperature set back when the temperatures are in the single digits.

Mike, as I said in my previous post the following manufacturers have 2 stage variable speed 40K furnaces:

Carrier/Bryant/Tempstar/Heil/Arcoaire/Comfortmaker/Keeprite/Day & Night

Lennox/Armstrong/AirEase

York/Luxaire/Coleman

Rheem/Ruud

Amana/Goodman/Daikin

That's pretty much everyone except AS/Trane. So there are plenty of options besides Goodman. Again I personally like the Amana/Goodman 90% furnaces, but I already spent enough time on that subject in my earlier post.

hvtech42, I stand corrected. I see the Carrier 59TP5 and 59TP6 2-stage furnaces are available in the 40K BTU size, so there are more choices.

I could be wrong, but a few years ago it seemed Carrier/Bryant did not have any 2-stage furnaces in this size.

Yes Carrier does have 40k BTU two stage furnaces available in the Performance series and I'm going to mention the 95 series one to my contractor. There aren't nearly as many 40k BRU two stage furnaces as single stage ones probably because a lot of small spaces are rentals or condos sold by developers so upfront cost is the driver. Still with the rebates I imagine the 60kBTU AS will be cheaper to install......go figure.

FYI I am going ahead with the following:

The 60kBTU two stage variable speed furnace (AUH2B060A9V3VA) will be used to heat the 800 sqft rental apartment. With rebates it's the cheapest to install. After rebates the cost for the whole install including a two stage thermostat and CO detector is $4.5k and $395 to remove the old oil tank.

An 80kBTU two stage variable speed furnace (AUH2B080A9V3VA) will be used to heat my 1550 sqft apartment. After rebates the cost for the whole install including a two stage thermostat and CO detector is $4.7k and $395 to remove the old oil tank.

Both oversized...if you get a true two stage thermostat that controls staging based on demand, you have turned nice 2 stage furnaces into a single stage furnace....but if you are happy, then so am I....apparently, the rebates are controlling your judgement...report back this winter...

good luck

IMO

Thanks for the comments. Yes, the rental apartment furnace is oversized, but the cost of installation is lower than a 40kBTU single stage unit and considerably lower than a two stage 40kBTU unit from someone like Carrier. Even if it only runs as a single stage it's the best option for me.

The 80k BTU unit is correctly sized. I would hope you'd trust both mine and my contractor's heat loss calculations rather than going on apartment area.

Is the larger apartment on the top floor? Is the house attached on either side? What R value did you use for the insulation? What were the indoor and outdoor design temperatures?

What software did you use for the load calculation? I am also skeptical that your calculation is correct. Fortunately it is a 2-stage furnace so it can run in the low stage most of the time.

"but the cost of installation is lower than a 40kBTU single stage unit and considerably lower than a two stage 40kBTU unit from someone like Carrier"

that statement alone does not make sense...any HVAC pro would know that the installation cost of a single stage high eff furnace should be no more and perhaps less than a 2 stage high eff furnace...regardless of brand...

Still skeptical about the 80 K for 1500 sq ft and think the sizing of both are a mistake. 50 KBTU on low stage will surely short cycle on low demand days.

Please report back when winter temps start kicking in.

IMO

For Mike

OP has effectively turned 2 stage furnaces into single stage models.

IMO

We have a government system that gives rebates based on efficiency numbers, but are blind to sizes. I think this is what is happening here. It costs the OP more money to get the smaller furnace. This what was happening a few years ago when the IRS was giving a $1500 tax credit for high efficiency furnaces and ACs. People were over sizing the equipment so they could qualify for the tax credit.

What the OP is installing is still a big improvement in terms of cost and comfort. It will be interesting to see how they perform in moderate and extreme weather conditions.

I used a spreadsheet. R values of the walls vary from R7 to R14 and I used a 64F design temp. difference. The larger apartment is on the second and third floors, rental is on first floor and both furnaces are in an unconditioned basement. The house is detached. Talking to my HVAC guy I am confident that I have made the best choice and sensible compromises give the age and thermal characteristics of the house.

Glad you reached a decision. I think you made the right choice. A good way to think about it is that you got a properly sized 40K single stage furnace, but you got an upgrade to the variable speed blower for free! That is much better than paying hundreds extra for the 40K single stage with X13 motor, or settling for their builder model with PSC motor.

The reason the rebates worked out this way is that American Standard is the ONLY manufacturer with a 2 stage furnace that hits 97% efficiency. The rest of the manufacturers (including the ones with 40K 2 stage models) are 96% or less, so they don't get the best rebate. I think the whole way the rebates are setup is stupid, since there will be NO practical difference to you as a homeowner between 95% and 97% efficiency, but that's a conversation for another day.

Absolutely disagree with above post especially about the X13 for the 40 K XT95 downstairs rental unit. Yes, there were initial issues upon roll out using this motor but were corrected and in my area I see no current issues with that blower motor. In fact it should be noted that all the brands including the so called Big 3 are using this motor in their furnace lineup both Sgl and two stage models. I am one that thinks sizing is important and have never liked the idea of taking a 2 stage high eff var speed furnace and effectively turning it into a single stage model. I agree that there are times that the rebate structure is incomprehensible.

60 K for 750 sq ft

80 K for 1500 sq ft

IMO

The 80k BTU unit is a great fit for my two floor apartment and I agree that the 60k BTU is a compromise for the rental unit, but it's an enormous improvement on the existing 40 or 50 year old York oil furnace.

I will post again with my experiences of the heating after they are installed. But given the previous large oil fired furnaces that were in use I imagine my tenant's and my experiences will be positive. They might be even better with slightly different equipment, but we will have no way of judging that. So I am predicting I'll say the new furnaces are great, but I won't be able to tell you if things could have been better.

In case you are interested in doing a load calculation, you can get a copy of HVAC calc for $49. Here is the link. It will be more accurate than the calculation you have done.

Thanks, but given the uncertainly in my R values I'm not sure that a more accurate calculation is that helpful. I have carefully measure the area of surfaces exposed to temperature gradients, the surface are of windows and doors and assumed an infiltration factor for an old home with some draught remediation. and assumed an extreme of 64 degrees. I have not applied the 15% to 20% safely factor recommended by the Dan Sleeth of HVAC- calc.

Tigerdunes, I agree that X13 reliability has improved, and I also think that a lot of the issues that it did have were due to putting it on poor ductwork.

However, my main point in that post was about price in this specific situation. I agree that I wouldn't pay more to get an oversized 2 stage furnace over a properly sized single stage furnace. But in this case, the single stage X13 would have cost more than the 2 stage variable speed because it didn't hit 97% AFUE for the rebate.

Locked on 1st stage, a 60K XV95 is basically a 40K single stage furnace with a variable speed blower. And reliability notwithstanding, variable speed motors are just better motors than constant torque ECMs.

So which would you rather have? A properly sized, single stage furnace with a variable speed blower for LESS money? Or a properly sized, single stage furnace with X13 motor for MORE money?

With the rebate the AS 60k BTU variable speed unit is no more expensive than a single stage "builders" 40k BTU unit so yes the rebate comes into it, and it is less expensive than any 40k BTU dual stage unit.

My choice really came down to either installing the AS 60 kBTU two stage furnace easily available from National Grid with a $600 rebate and the same as the 80k BTU unit, apart from a couple of burner, that I'm also installing, or getting a more expensive (probably at least $500) Carrier 40k BTU 2 stage unit........or going with something like a 40k BTU Goodman 2 stage unit. As I won't be paying for the fuel to run the rental furnace I chose the lowest installation cost and as a landlord I also like having furnaces from the same manufacturer.

I have a very general question about variable speed furnace efficiencies. If this were a boiler or heat pump, we might expect higher efficiency when operating at its lower speed/capacity. Is that true for furnaces?

Depending on the homes' air leakage rates, this might or might not be significant: Don't forget that with the higher performance furnaces using outside combustion air he is getting rid of what amounts running an exhaust fan the whole time the furnace is fired up.

Efficiency is slightly less on low stage, but by such a small amount that it wouldn't be noticeable on your gas bill.

However, 2 stage or modulating won't save energy, either, over a single stage furnace of equivalent efficiency.. It's strictly a comfort benefit.

Furnaces which short cycle tend to waste fuel. If the 2-stage furnace eliminates short cycling then there may be a small gain in efficiency improvement.

Just to update this thread. The 60kBTU AS Freedom 95 (two stage, variable speed) furnace is half way installed. Final plumbing and electrical (two stage Honeywell thermostat and hardwired CO monitor) will be done tomorrow and then the burn in. The only annoyance was finding a suitable vent location on the side of the house to avoid windows. The installers have left me a load of tape with instructions to tape the joints of the existing ductwork....they did not contract to do that.....but urged me to do it as it's "so easy".

The oil tank removal and my 80kBTU furnace install will be dealt with next week.

Duct tape or mastic tape? Don't waste your time with the former. Use the latter.

Thanks, Snidely, fixed now.

I think you've got your formers and latters mixed up.

Foil tape with a mastic sticky part is what should be used, forget about duct tape. Duct tape isn't for ducts.

Foil tape.

The worst bit of this new furnace is the ugly white PVC sticking out of the side of the house.

FYI the first floor furnace is up and running on a Honeywell TH6220 thermostat. I talked to the guy while he was installing it and he said he'd had a high efficiency furnace for 7 years......and didn't like it as much as his old simpler 80% efficient furnace as he'd spent $1000 on repairs. Man what a buzz kill......still I argued that he was an early adopter and that's always expensive and anyway, if the furnace does need repair he should thank me because I'm keeping him in work....that got a laugh.

We set the default schedule and tested the furnace going from 61 degs to 68 degs. The blower was pretty strong initially, but once it got to set temp it throttled right back and I was just in the apartment and its at 68 degs and there is just a faint flow of air from the vents and zero noise.

furnace is operating on low stage only?

Good question. How would I know that the 2nd stage is on other than by the temperature of the air from the vents? Is there an indicator on the furnace or thermostat or do I have to get in there with a multimeter and check a relay?

The technician initially couldn't find the extra wire for the 2nd stage as it was hidden in the wall so we discussed using the furnace board to control the 2nd stage until another wire could be installed, but the wire was already there so that wasn't an issue. I assumed the furnace came on in 2nd stage as the delta from set point was 8 degs, but I didn't specifically ask the tech. I will do that when they come back next week to install my furnace.

Using furnace board timer is a no no and absolutely defeats the purpose of a nice two stage vs furnace effectively turning it into a single stage model that goes to high stage whether needed or not. Ask dealer how you can tell. If my decision, I would have high stage decommissioned. BTW, you can't tell from temperature and difficult as well from air flow.

IMO

Using the furnace board was only suggested as a temporary fix when the tech couldn't find the wire for the 2nd stage so the tenant could get heat as the electricians had gone home and it was late in the day. It wasn't necessary as the wire was there, just tucked into the wall. I will ask the dealer about the furnace performance next week, but going from 60 degs to 68 degs the temp and velocity of the air from the vents was high and an hour later the temp and velocity of the air was a lot less. I assumed that the furnace was in second stage for the 8 deg delta-T and then went to first stage to maintain the set temp, but I'll double check.

I would say it is on high stage just from your description in above post but it may have dropped back to low stage at end of cycle when stat was satisfied.

IMO

I talked to the dealer today and the furnace has been tested. The electricians tested the continuity of the wires and they were good. A combustion test was done and is ok and the second stage did come on when the set temp was 8 degs above room temp and the technician just checked that visually.

Here is a before and after shot.

maybe 40 or 50 year old York oil burner

New American Standard Freedom 95 Gold 60kBTU furnace.

FYI, both of my oil furnaces have been replaced by American Standard Freedom 95 two stage variable speed gas furnaces. An 80kBTU AUH2B080A9V3VA unit for my two floor 1600sft apartment and a 60kBTU AUH2B060A9V3VA unit for the ground floor apartment. The reasons for choosing those furnaces are covered earlier in the thread. The old oil tanks have also been removed. The cost of the complete job after $1200 in rebates was $10k.

The weather hasn't been cold enough yet to give the furnaces a good work out, but they are very quiet and keep the temperature at the set temp without me even noticing anything.....no clunks or high velocity air coming out of the vents

Excellent! I see you had to make some compromises with the equipment/install; hopefully it will all work out for you and your renters.

Not exactly compromises, I ended up with a couple of excellent systems at a good price. The renters are very happy with the heat in their apartment and removing the two oil tanks has freed up a lot of space in the basement.

Great HVAC....nothing special about pricing....but both furnaces oversized...if you have true 2 stage thermostats, you will never need high stage on either system...

Thanks for the comments tigerdunes. We've been over this quite a bit already. The pricing is average for the North East....labor rates tend to be quite high and the $600 rebate makes the price of the furnaces excellent. I obviously have two stage thermostats and the sizes of the furnaces were decided after heat loss calculations. I live in an older home in a cold climate and my calculations were within 10% of my contractor's. The calculation for my two floor unit came in at 75kBTUs. The contractor initially wanted to install a 100kBTU unit, but I talked him down to 80kBTU. The furnace for the renters below me is a bit large, but it was the smallest two stage available from American Standard. I thought about installing a 92% efficient 40kBTU single stage furnace with selectable motor speed, but as the 60kBTU two stage with variable speed motor was the same price after the rebate I went with that one.so that both furnaces essentially the same and to get the variable speed blower. I imagine having the second stage will also be nice on very cold mornings.

Did you have two oil tanks removed? Removing oil tanks from old houses requires a lot of labor and they have to be disposed properly. That adds quite a bit of cost to the project. Overall I think the prices you got were good. You probably saved a little money by having both furnaces done at the same time.

With were above 70 degrees in the New York city area on Christmas eve. At this rate you may not be able to enjoy your new furnaces this winter!

Yes, both oil tanks were removed. The cost for each was $395 and was included in the total cost of the job.

It's been pretty warm in MA too......that design temp of 6F is looking very conservative......still there's lots of winter to come.

for OP....my comments were directed to those who might be following this thread...I am a great believer in sizing HVAC correctly....I am certain this did not occur on these new installs...

TD

tigerdunes, I know how you like to size correctly, but as you have no direct experience of my home and the calculations and measurements that were done I assume you are basing your conclusions on square footage and your general experience. While I'm sure that is great, I give more weight to the detailed calculations done by myself and my contractor. It seems strange to always insist on a load calculation and then ignore them when they are done. The 80kBTU furnace I chose is right for the 75kBTU calculated heat requirement and the rental unit is a bit large, but was installed for reasons I have explained. If I was to insulate my 1920s two family a bit better I accept that a 60k BTU furnace would probably work nicely for my apartment.

A month ago I replaced a 25 year old 140k BTU Hallmark furnace with an 80k BTU AS two stage gas furnace with ECM. Last year oil cost me $1k. I just got the first month's gas bill. It's never nice getting a bill, but this one was quite pleasant to read as it was $100 for the month and I estimate $80 of that was for heating. So assuming a 5 month heating season I'll only be spending $400......which is a lot less than with the old oil furnace even with oil at under $2/gallon.

Also without the oil tank and with the far smaller foot print of the gas furnace vs the oil furnace, the basement has far more useable space.

Ecm blowers are supposed to save elctricky too!

Yes, but my electric bill is already small so the saving for that won't be enormous. It looks like the new furnace will be cutting my heating bill in half and will pay for itself in around 10 years.