The copy is difficult to read, but it looks like the total cooling requirement is 4.19 ton. I going to assume the 5 ton 13 SEER AC is a single stage. You should ask why a 5 ton when the Manual J is specifying a 4.5 ton condenser. Why bother doing a Manual J calculation if you are going to ignore it.

A 3250 sq. ft house should have a system for each floor. I have a similar size house in central NJ and have two systems. It is the only way to get even temperature for the two floors. I think you will have problems trying to zone a 5 ton single stage condenser. Most 5 ton systems have undersized duct work. Many HVAC contractors don't do zoning well. I would not trust the contractor without confirming his zoning ability.

You already have R50 in the attic (Manual J says R38), and R19 walls so I am not sure if 2 inches of foam are worth the added expense.

I suggest you upgrade to two systems (2 tons for each floor should be fine) with variable speed 95% AFUE furnaces (SEER 15-16). You may want to upgrade to heat pumps and create dual fuel systems. What is your electric rate and do you get a break if you have a heat pump.

The heating load is 88K BTU. The furnaces can be 60K BTU each. The idea would be to use the heat pump most of the time and the propane furnace would be the back up. You could also forget the propane and use electric back up. The propane is nice for domestic hot water, clothes drying, and cooking. You should consider this route if you think you may be hooked up to a natural gas line in the future.

Lithnights. I don't know much about HVAC units but I have been through this as a consumer. I can't read your attachment, but I will tell you that I was just through all this when I replaced my HVAC in Atlanta. What I learned is that a detailed load calc has to be done ( I would have it done by a couple of different companies). In my experience, they almost always err on the side of giving you a bigger system. The don't give you the proper credit in the load calc for added insulation, low e windows and other things. This does not benefit you as a bigger system equals higher energy bills and LESS comfort due to short cycling etc. There may be a reason why they are not going with 2 units. Maybe they can't at this point. But, you need zoning to be comfortable. At least two zones and possibly more depending on how your house is laid out. As I am sure you know, the downstairs needs will vary greatly from the upstairs. For this reason, I would want two units.

I question the value and conclusions of the Manual âÂÂJâÂÂ.

âÂÂTotal Cooling Required With Outside Air:

43,314Btuh
3.51 Tons (Based On Sensible + Latent)
4.19 Tons (Based On 75% Sensible Capacity)âÂÂ

How can you require a larger system (4+ton) based on 75% sensible load than a system (3.5+ton) that is based on full load - sensible AND latent!

I am going to say something here that IâÂÂm sure I will be savagely attacked but too much faith is placed in these Manual âÂÂJâ calculations. As long as someone can wave a piece of paper around with a bunch of numbers that says Manual J itâÂÂs as if its come down from on high. Well no so fast, just like HVAC performance is all about the quality of the installation and not necessarily the brand of equipment installed, so is the Manual J.

Many contractors have poor software or none at all. However good calcs can be performed without any software. Many contractors - including those with good software - donâÂÂt know how or will not take the time to run it effectively, garbage in, garbage out!

Be careful about whatâÂÂs written (or scribbled) on a piece of paper.

IMO

SR

One system with zoning controls. Must have dealer though with demonstrated experience in this area of HVAC. Two properly sized systems preferred though.

Good post by FSQ. I would say though that if Man J numbers look suspicious, then have it performed by a third party or do it yourself{{gwi:807}}. Will pay off in the long run.

I can provide a link if interested.

Your main question that needs to be answered is whether dual fuel systems or go all electric. If you provide your electric rate and cost of propane, I will run a quick fuel comparison calculation that might be helpful in your decision making.

IMO

This post was edited by tigerdunes on Mon, Jun 10, 13 at 14:42

I agree two units. Electric back-up not a problem if LP is expensive and house insulated well.
Questions about the importance of heat loss see link.
http://www.comfort-calc.net/faq.html

Thank you for all the replies. Here are answers to the questions I saw..

Propane is about $3 a gallon.
My electric is $.16 kwh
I believe there may be some kind of break for a heat pump but I haven't looked into that fully.
I am not sure which backup would be more ideal (propane vs. electric) but I think the last time I ran the numbers (using the multipliers from a cost of heating worksheet), propane came out cheaper.

I am not as concerned with the heating aspect of the proposed setup since I plan to run my fireplace for most of the heating of the home. I figure the downstairs would be warm enough from the fireplace, and the 2nd floor would have it's own zone (either with zoning or a separate unit). I'm more concerned with the cooling impact (having it too hot upstairs in the summer).

I would be interested in any link where I could run my own manual J or analysis.

I am thinking of having another HVAC guy look at the numbers, but then it's just their opinion vs. the first guy's opinion, no? I actually had a 2nd HVAC guy walk through it already with me, and although he liked the work he had seen, he did disagree with some of the proposal/design. So it's almost like I need TWO more opinions and compare all three.

I am meeting again with the HVAC guy tomorrow. Are there any questions I should ask them about the analysis and their proposal? e.g. why are you proposing 5 ton when the numbers say 4 tons AND that's not even taken the 2" of spray foam into the equation?

Thanks all!

Fuel comparison calculator

Used your rates.
95% eff for propane furnace
2.75 COP for heat pump which is on conservative side

Cost per 100,000 btu of useable heat
Electric baseboard: $4.22
Heat pump: $1.70
Propane: $3.45

You do need to check with electric supplier for special heat pump rate.

Also attached link for software to size HVAC.

IMO

Here is a link that might be useful: HVAC Calc Software

If this is a location that can lose electrical power in winter, then the propane backup would not be such a bad idea.

if you have a generator.

Tigerdunes, your figures look like what I had run. I think I used 2.75 or 3 COOP so heat pump was no doubt the cheapest, and then the propane was cheaper than the straight electric for backup. I will check out that link.

Weedmeister, we can lose power but it's very rare, especially during heating season. Most power outages are in spring/summer/fall due to heavy rain. And that's less of a concern b/c my fireplace should be able to keep us warm enough, even with an extended power outage.

I do plan on installing a whole house generator (supplied by the propane tank which I will have anyway..for cooking/dryer/how water) in the next couple years.

So, are there any other questions I need to ask the HVAC guy or challenge him on any part of his proposal? e.g. Why using 5 ton? Why only using 13 SEER which is govt minimum? etc.

If you are leaning toward a DF system with propane backup, then I would look at Carrier's relatively new low temp GreenSpeed HP and GreenSpeed Infinity furnace. Carrier is known to have perhaps the best integrated system with their Infinity zoning controls. Worth a serious look. Dealer though must have demonstrated experience both with GreenSpeed HVAC and Infinity zoning. Since you woud have propane for your backup heat, it would also e available for your generator.

IMO

You are going to find that builders and general contractors know very little when it comes to HVAC. They will also want to spend as little as possible on equipment and installation. The theory is HVAC is not a high priority for home buyers so there is little incentive to spend the extra money. Later on it becomes the buyer's problem when the house is uncomfortable and the energy bills are high.

While I agree with TigerâÂÂs above post regarding dual fuel and Greenspeed, have you considered geothermal?

You could have a COP of 4 or better and use it to heat or pre-heat your hot water.

SR

I met with the head of the HVAC company (which by the way does have a good reputation..not some fly by night company..if that matters) yesterday and expressed my concerns. He reassured me that what they were installing would make us happy. Of course it will!! : )

I did mention that when they did the analysis, they didn't consider the likely 2" spray foam, and he agreed that they would need to rerun the data. SIDENOTE: I just got the spray foam cost and now I am thinking I won't be able to do it anyway. So 5 ton may be what I get anyway.

I asked about 2 stage and he suggested against it for my situation.

Still not sure about the zoning or not. I'm tempted to NOT do it, since the HVAC owner assured me that I'd be happy. He mentioned if not, within the first year, they will come out and make it right. So I was thinking IF I'm not satisfied, within the warranty, I would ask them to come out and make it right. Maybe at that point, it would show that zoning or 2 units WAS indeed necessary. As opposed to doing it upfront. But then I think I may need it anyway b/c my wood fireplace will heat up the 1st floor enough, and the 2nd floor will likely always be cooler. A second zone/thermostat will resolve that. I don't know...

This post was edited by lithnights on Wed, Jun 12, 13 at 14:24

Regarding some of the latest comments, I had researched the Greenspeed many months ago and liked what I saw.

My concern is that these guys are York guys and I've read that the Greenspeed can be a tough install to get right if you don't know what you're doing. Bottomline, I'm not sure I trust the HVAC guys to do it.. even assuming they would do a non York install.

I had looked at geothermal as well but I simply don't have the lot space to run the pipes as needed. Nor the much larger upfront expense.

So exactly what is dealer proposing? Brand, model numbers, sizing?

One system without zoning controls? If so you are headed for trouble.

IMO

I am going to repeat the advice I gave earlier. Spend the extra money on two properly sized systems. Use the money you were planning to use on the spray foam. You will be more comfortable and the operating costs will be lower.

I would be suspect of a HVAC contractor who is against zoning and separate systems. It seems the contractor has made a decision as to what he is installing and does not want to change the plan. I would not rely on his warranty to satisfy your problems. It is better to have the fight now, then a year after you are in the house.

Mike,
Just to clarify, I wouldn't say the HVAC guy is against zoning and separate systems. He's using the line of "the analysis told me to do one 5 ton unit. You could do zoning or 2 units at your cost, and I would suggest doing zoning".

At this point, I am having a builder friend have his HVAC run an analysis (small fee) AND I may end up using that $49 product that someone had posted a link for at some point.

I hear you about doing 2 units. But the $6K extra cost to me (not in budget!) is tough. SHOULD it really cost that much more to add an extra unit? I just don't understand the cost. Is the extra heat pump, components, piping, extra blower etc. really that much? The materials can't cost that much, can they? Ok, there's more labor, but could labor really be that much when all their doing is running some extra wiring, extra thermostat, and the copper pipe run from heatpump to the indoor coil? Maybe I'm ignorant but I just don't get it.. $6K? there's no extra duct work material or labor to run ductwork! What am I missing?

And of course they never gave tonnage to what the 1st unit would be and what tonnage that extra unit would be. Nothing like lack of details..

"the analysis told me to do one 5 ton unit."

I would love to see the analysis that shows to install one over sized unit versus two properly sized units.

Two furnaces and two AC condensers or heat pumps require two sets of supply duct work. You could share one a common return. This is how it was done in my house. It is not ideal, but it can be made to work.

Adding the second furnace, condenser, thermostat, wiring, duct work, and labor for $6K is reasonable in my opinion.

I understand if it is not in the budget. How much does he want to zone the first and second floors?

I also become concerned when the AC reaches the 5 ton size. Most houses don't have the properly sized duct work to handle the required 2000 CFM of air flow. Having two smaller furnaces and condensers makes it more manageable in most cases.

You should familiarize yourself with the thread by ellessebe. There are several. He is in big trouble.

There may still be time for you, not certain though.i really feel your GC and his HVAC sub are taking you for a ride down the garden path. It seems you are inclined to follow.

IMO

Mike, I've been asking for this analysis for over a week. Asked builder and asked HVAC guy directly. Getting the runaround, and I feel like I'm being forced into this decision. In fact, over a month ago, I emailed the builder asking for the Manual J analysis. Never replied.

They quoted me $3600 for the 2 zone system. I am almost forced to do either a zone or 2 unit, b/c I will have a high output wood fireplace that will be the main heating source, which will make the 1st floor very warm, but may not get up to the 2nd as much, so I'd at least need a thermostat upstairs. Conceivably, the 1st floor zone, or 1st floor separate unit may never even go on in the winter (I know a guy who has the same fireplace and similar size house and his furnace didn't even kick on last year), but the 2nd floor would def need to kick on to keep it warm enough.

I'm ready to tell the builder that I'm not moving forward with HVAC until I get a full analysis that I requested over a month ago and the chance to run it by another HVAC guy or 2.

tigerdunes, I will check out the thread by ellesseb.

I don't want to follow the path but I'm not sure what LEGALLY/CONTRACTUALLY, I can do. They will argue I am holding up the process, but I will argue that I've been asking for a full analysis for over a month now. I'm not sure who wins that battle.