This contractor sounds lazy. He'd be surprised with what a load calculation would show. Has he examined the ductwork to make sure it can handle 5 tons? Many times there isn't sufficient ductwork for 5 tons...

ryanhughes...
Thanks for the link to the Trane Commercial site in the other thread.
Only 3.5-ton??? Really makes me wonder about these contractors. My calculation of sq. ft. is 2,778 for 1st and 2nd floors plus 1,242 for unfinished basement. I even measured all of our windows=641 sq. ft. One guy did measured the return duct and the exiting duct and said it will handle a 5-ton. But I guess that does not mean I really NEED a 5-ton. I will keep trying to get a Manual J done. If I can figure out that software program, I'll try to do it myself(?). Thanks... Gary

I'll attach a link to a good program to run the calculation yourself. There is a $49 fee, but I think it's worth it... I think it will be interesting to see what you come out with. You'll have to know your insulation values, but from what you posted above, it seems like you're already on track with all the info. Good luck.

Here is a link that might be useful: HVAC Calc

Before you buy the program and run it yourself, I'd call and "screen" a few more contractors and ask them right on the phone if they'll run the load calculation (Manual J). If they refuse or make up an excuse, move on--save your time and theirs.

ryanhughes...
Well, I downloaded the Manual J program and filled it in. Too curious, so I purchased it. Not sure how to interpret the results but here are a few figures it gave me:
Sensible Gain: 29,945
Latent Gain: 2,396
Total Heat Gain: 32,342 (2.5 ton)
Total Heat Loss: 79,715
I hope I did it correctly. I did the floors, walls, ceiling, windows, basement, skylights, fireplace...
What do you think???? I currently have a 5 ton A/C and the gas furnace is 167Kbtu. Gary

Do you know the current efficiency of your furnace? If you entered all of the information right, then you're way oversized on the A/C and oversized on the furnace (not sure about efficiency). Did you enter insulation values? And just imagine, these contractors didn't want to do a load calculation because you already had a 5 ton! I would go with a 3-ton unit (single or dual stage) with a furnace to match your heat loss (size depends on efficiency). Being that oversized is surprising. How did the old 5 ton keep up? Can you state your location and square footage again? Thanks, and good luck.

Manual J calculations on older buildings can range from 'quick and dirty' to detailed and accurate.

Even a small change in the exterior wall insulation value can have a large impact since there are so many square feet.

Infiltration losses are also a significant factor in most houses, and 'estimating' them takes experience.

Metal windows (used in at least some of the Reston houses) have large losses.
Metal storm windows reduce infiltration, but NOT heat loss (you cannot have any real temperature change across the metal, it conducts heat to well).

There are a number of ways to 'check' an older house system for the required capacity, but not many HVAC contractors have the knowledge or time.

Many send someone to a weekend class to learn how to drive a Manual J tool and they are off and running.

ryanhughes...
My current gas furnace is about an 8 Seer. Location: Reston, VA. I think I entered the data correctly. I might be off some but not much I think. I have a garage so I excluded the garage's floor space when calculating each floors sq.ft. But I did not not exclude the garage's wall space from the wall's sq.ft. since there are insulated walls in the garage.

Here's the data (interior measurements):
1st Floor-1,242 sf.
2nd Floor-1,476 sf.
Basement- 1,242 sf.
Bay windows floor space-60 sf.
NE 1st Floor wall-408sf; windows-130sf
NE 2nd Floor wall-408sf; windows- 68sf
SE 1st Floor wall-256sf; windows- 0sf
SE 2nd Floor wall-256sf; windows- 40sf
SW 1st Floor wall-408sf; windows-217sf
SW 2nd Floor wall-408sf; windows-123sf
NW 1st Floor wall-408sf; windows- 37sf
NW 2nd Floor wall-408sf; windows- 28sf
Skylights: SW 27sf 45 degrees
NE 9sf 45 degrees
Ceiling- 51'x32'
Standard insulation- 4" in walls; 7" in attic.
Misc: 2 people; 1 fireplace; kitchen btus were added.
All windows are new vinyl thermopane.
New vinyl siding with the Dupont Tyvek.
House is very tight.

Can't think of anything else I added in the program.
Don't think I could be that far off to bring it down from a 5 ton to a 2.5 ton. Little scary!!
I can send you PDFs of all the reports,if you are curious.
Gary

The problem with doing a manual J on an existing house is the insulation values can be a mystery. Do you know for sure what the R value is for the walls? You can usually see the ceiling insulation but sometimes can be matted or an unknown material. So there may be some guessing there. Infiltration is also an educated guess.
This isn't to say a calculation shouldn't be done.
You can play with some of the numbers and come up with a worst case situation.
I have a feeling you will end up with a 4 ton. Maybe a 3.5 ton. Most of the typical problems for a second floor is ductwork related. You will want to make sure you get enough air upstairs, especially return air.

funnycide...
I played around with the Infiltration choice. I changed it from 'Best' to 'Avg' and it changed the 2.5 Ton to 3 Ton. (35,700 Heat Gain; 92,495 Heat Loss). But our house is very tight. When built, additional insulation was added; extra caulking; all new vinyl thermopane windows; Tyveck house wrap. I even sneaked in at night and caulked and insulated where the builder did not...
Gary

Gary,

What I would do now is contact the contractors who you liked (or new ones) and explain what you've done. Ask them if they're willing to take a look at your results (print out a PDF of the summary) and share their thoughts. It would be better if they were willing to do their own calculation, but in the real world few will. It is surprising that, for around 4000 sq. ft., a 3-ton unit is all that's needed (I upped the tonnage based on what you described and the calculated btu's) and you originally had a 5-ton unit. Do you know roughly how many supplies and how many returns you have in your house? For example, I have 3 central returns and around 30 or so supplies in my house in total (remember for a 3.5-ton unit). I'm concerned with getting the airflow throughout the house when the ductwork may be oversized for the required tonnage to begin with.

Tweaked it some more for worse conditions. I changed the Infiltration from Best to Avg; Changed the Design Conditions's summer temperature (Winchester's set) from 90 degrees to 95 degrees; Winter left at 10. Inside conditions: summer=74; winter=72.

The results changed to 3.5 Ton. (39,841 Heat Gain; 92,495 Heat Loss). Still not close to 5 Ton.
Interesting... Gary

And you're still not quite at 42,000 BTU/H (3.5 tons), so that's good. Sounds like a 3.5-ton might be a good option. You can play around with it and see if you missed something or there's something you can tweak. I think adjusting the design temps is a good idea. 10* should stay where it is in my opinion, though. Based on your calculation, 3.5 tons would still be oversized, but not grossly. I'm guessing the 5 ton was terrible at controlling humidity and ran short cycles? You're doing well Gary--I'm sure it's been education for you as well.

Did the heat loss change? What furnace efficiency were you planning on going with? This will determine the capacity of the furnace you select, taking into consideration the heat loss value.

The creator (I believe) of HVAC-Calc is also the founder of a major HVAC forum at HVAC-Talk.com (link below). There are many pros on that site, and they seem very willing to assist people in situations such as yours, especially since you've purchased the program that they recommend! I'd register there for some more advice regarding this, since I'm not a professional--not even in the field, just a person with a great interest for the subject. Post in the Residential HVAC forum.

Here is a link that might be useful: HVAC-Talk

ryanhuges...
Yes...good idea. I have a contractor coming tomorrow. Highly rated in Checkbook magazine. We had a talk the other day on the phone about doing a Manual J and he wants to charge several hundred dollars to do one. But he seems to be more up-to-date with this stuff. I'll show him what I've come up with.

I have 2 returns; and 12 supplies on the 1st floor; and 14 supplies on the 2nd floor.

So if I have ducts a 5-ton, getting a smaller tonnage, say 4 ton, is not good??? I feel like I'm a detective. :-> Gary

Gary, I'm not sure about the ductwork 100%. In a sense it seems like it would make the system quieter, but in another sense I would be concerned with loss of velocity--I don't know. This would be one of my major questions for the contractor tomorrow. 2 returns sounds low for a 5 ton unit--that's roughly 1000 cfm per return, assuming you are getting 2000 cfm to begin with. Are they noisy? I'll check back tomorrow to see what this contractor has to say.

The problem with this is that any calculation is only as accurate as its least accurate variable. When you "guesstimate" here and there to fill in a form like this, you come up with a lot of specific numbers that look impressive, but what do they mean? In an existing house, there's a lot that's hard to know about the necessary values.

One suggestion to "reality check" this: Think of how much your current heat and a/c run on really hot/cold days. This is telling you how close your current system capacities are to the TRUE heat loss/gain of your home.

ky114...
I agree that "any calculation is only as accurate as its least accurate variable." But if the contractors don't do any calculations and only do a guessimate and say they will just replace what you have because it must be 'good enough', at least someone has come up with some way to analyse what is going on with this program. Yes, it's a bunch of numbers. At least it gives you more to chew on. How do I do a 'reality check'? Everything seems to work OK. Hard to compare it to anything after being with the current system for 22 years. You kinda get used to it. It might run Ok but maybe by tweaking the system, my bill might drop and I'd be wasting less gas and electricity. That is where I would like to make a difference. Each contractor has given a different setup of equipment. I was hoping they would be pretty close and I only had to choose who had the best price. They are not making it easy to spend a lot of money... Gary

The problem you're up against is that most people are primarily concerned with price and brand name. They're going to get three or four estimates and then take the cheapest, or some will opt for the most expensive, deeming it "better quality."

What I was suggesting with the "reality check" is to do some thinking about the conditions you experience in your home with the current system. Does the a/c or heat run most or all the time on a very hot/cold day? If so, this indicates sizing that's at or close to what you need. Does the house seem damp when a/c is on? This tends to indicate oversizing. Does the a/c or heat run in short cycles? This also tends to indicate oversizing. Is airflow distributed well? A "no" here might indicate need for ductwork revision, more powerful air handler, etc.

You also have to think about what you are and are not willing to tolerate. Is it a problem if you can't get the house below 78 on the warmest days, or are you someone who likes to be able to hold 72 degrees no matter what? That factors into whether or not you want to downsize the equipment.

Also, on the issue of energy saving, reduced equipment sizing is not an energy-saving panacea. It has some impact, but it's not as important as a house's tightness and insulation effectiveness, indoor setpoints, willingness to use setbacks during the night and unoccupied periods, and the efficiency levels of equipment. The only thing you're saving with smaller equipment occurs in the time it takes for efficiency to ramp up to the design level after the equipment starts up, as the smaller equipment should probably run in longer cycles and spend less time in that period of reduced efficiency. Compared to the other factors affecting energy use, that's a relatively small issue.

Gary,

What KY is saying is logical. It may be hard to tell whether or not a system is right since you've lived with it for years and years, as you've mentioned. If you're confident that what you entered is on target, as you are, then I'd go over what you found with a couple GOOD companies and get their input. They may say something crazy, or they may say that you've been living with an improperly-sized unit for ages (which is what I hope they say to confirm your calculation). I guess we'll see how tomorrow goes with the contractor. A dual-stage unit gives you a little more leniency; however, proper sizing is still key, as you know. With a dual-stage unit (I'm not sure if you're planning on going this route), the first stage of cooling (or heating with heat pump) is less, so it will run longer and remove more humidity. I take it you didn't notice any significant issues with the old 5 ton?

Wow. I can now see why I could not find any contractors to do one of these suckers either. It almost sounds like you are better off repalcing with the same size equipment you already have(assuming it is working well) rather than rely on
1) yourself trying to do the J
2) a contractor trying who does not typically do the thing, attempting to do the thing

It seems this thing is an art and your really need to know ALL detail of your home to get an accurate mesurement. After reading all this and NOT know explict details of the inner walls of my home and NOT having confidence in any of the contractors I saw to do the calcs (even if they would) I think I am actually safest just staying with the size unit I have now.

I did give our contractor the 20 year old house plans , he looked for upgrades made since then house was built and he said he did work up some numbers and eventually suggested staying with the size unit we already had. I have no idea what calcs he did but at least he asked for the plans!

Well, you don't want to throw out the baby with the bathwater, Andre, but there is a reason contractors aren't running around doing these Manual J calculations and downsizing everyone's equipment. Also, I do know of a case where a contractor downsized a furnace based on a Manual J and in the past few winters the family has had to supplement the furnace with electric heaters to get the house over 60 degrees on really cold days. The problem, of course, is not with the Manual J, but probably to some extent with the person who did it, and, as you pointed out, a lot of stuff is practically unknowable when you're talking about existing construction.

So, what happens is you wind up throwing fudge factors into the Manual J to provide a margin of safety, because you don't want that call at 3 a.m. saying, "My family's freezing."

I agree with you that staying with the same size equipment is often not a bad option if in making that decision you consider some of the questions I mentioned above. There are cases where equipment should be downsized, but, truthfully, 20 to 25 years ago they were not oversizing that badly on new construction. On older construction, maybe so, because the furnace and a/c put in during the 1980s may have been identical replacements of stuff installed in the 1960s.

KY, question for you (regarding my personal home/load calculation for my home done by a pro):

If you got a result of (I don't remember for sure, but I remember the range) 43-45k btu's of heat load (through a Manual J performed by a competent person) on a home that originally had a 3.5-ton system, would you upsize to a 4 ton? The current 3.5-ton system we have seems to work fine and even cooled the home to 72* during the east coast heat wave (of course running near constantly). The comfort now with the 3.5 ton is great, but I'm not sure if upsizing to a 4-ton system would be ideal. I ask you since you seem to know a thing or two about sizing equipment. The contractor proposed a 4-ton system, which I haven't had installed yet. I worry about short cycling and higher humidity. Do you think a 4-ton system would be a problem, though it may be slightly oversized? Another issue was getting more airflow, which a 4-ton system would provide without losing too much latent capacity by increasing blower speed on a 3.5-ton system.

Thanks. Sorry for cutting in to this thread Gary, but it's pertinent. :)

KY, question for you (regarding my personal home/load calculation for my home done by a pro):

If you got a result of (I don't remember for sure, but I remember the range) 43-45k btu's of heat load (through a Manual J performed by a competent person) on a home that originally had a 3.5-ton system, would you upsize to a 4 ton? The current 3.5-ton system we have seems to work fine and even cooled the home to 72* during the east coast heat wave (of course running near constantly). The comfort now with the 3.5 ton is great, but I'm not sure if upsizing to a 4-ton system would be ideal. I ask you since you seem to know a thing or two about sizing equipment. The contractor proposed a 4-ton system, which I haven't had installed yet. I worry about short cycling and higher humidity. Do you think a 4-ton system would be a problem, though it may be slightly oversized? Another issue was getting more airflow, which a 4-ton system would provide without losing too much latent capacity by increasing blower speed on a 3.5-ton system.

Thanks. Sorry for cutting in to this thread Gary, but it's pertinent. :)

Ryan, in general I'd stick with the size you have in there if you as a homeowner attest that it's working well, but in this case I think the contractor has given you some justification for his position (increase airflow without sacrificing dehumidification).

Also consider that the true capacity of these systems does vary. The nameplate rating is a nominal figure. What if, for example, your current system that's rated at 42,000 BTU is really moving 44,000 BTU of heat, and what if the replacement 3.5 ton is really moving 40,000? I realize that that could just as easily swing the other way, so it's not really a point of decision-making, but it is mainly said to put it into perspective that a 6,000 BTU difference in capacity is not a huge difference.

A couple things tilt my opinion toward the 4-ton. First, that's what the contractor wants to do, based on experience in your area, and taking his recommendation also puts you in a better position if you have problems related to sizing. Second, you mentioned keeping your house at 72 degrees, which is a relatively cool temperature. Generally people who like 72 are not comfortable at 78, and IF the new 3.5 was not as effective as the old one, I could see that you might not be happy since your house could be warmer than you like.

ryanhughes...
The next contractor came today. I did not know it but he only does York. He will be sending his bid to me later. I have no idea where York stands in relation to Trane. I really liked his attitude about everything. He has the highest Checkbook rating-94%. But I don't know anything about York. This Forum didn't have too much to go on. He talked about the York 'modulating' unit as probably being in his recommendation. He said the trend will be to go from the 2-stage to the mod. units. He also said that York is best in the electronics. Got any feel for the York brand as far as reliabilty, etc. Thanks... Gary

York is fine equipment, especially their Affinity line of equipment (quiet). The modulating "mod" furnace is a nice furnace (Affinity line). What did he say about sizing?

Thanks KY. I understand the varying capacities, and that's why I use ARI to double-check them. I've been looking at Trane and Lennox equipment myself, and I do see that, especially for Trane, the heat capacity is lower. I'll let the rest of the thread focus on Gary's situation. Thanks.

* Posted by ryanhughes (My Page) on
Wed, Jun 18, 08 at 14:44
"York is fine equipment, especially their Affinity line of equipment (quiet). The modulating "mod" furnace is a nice furnace (Affinity line). What did he say about sizing?"

Good to hear positive note on York. Though he has not given me the components yet, he seems to be leaning toward the 5-ton since my ducts are sized for it. And I think he is in the 100Kbtu for the furnace. The 'modulating' thing sound interesting to me. Talked about putting a canvas connector in the input and output ducts. He spent some good time explaining what he wants to do. So, it seems now it will be Trane vs York... Yet another contractor is coming tomorrow.

Oh, yea. He does not like flushing the line set. He says it is safer to replace.
I'll let you know the details when I get them.
Gary

I'll do the calculations but I charge for it.

howdy rbadger! Long time!
and OP...he knows his stuff and is well worth the cost.

There are ways to guess and ways to make an educated
acessment. When home was built will give you a good idea
of wall insulation R-value. Measuring insulation depth in attic is also easily ( although sweaty..) R-value.

testing home for duct leakage and house leakage and sealing
these leakage areas will give you an accurate infiltration
number to input on your load calc. (and good for you..hvac-talk is great isn't it!)
I use a blower door to do the diagnostic/testing, but some folks use both a blower door and duct blaster.
Also a 'tight' house is easier to heat and cool and knowing where to seal the ductwork is the way to downsize the system, have lesser utility costs & improve the comfort of the house.

Best of luck with your project.

ryanhuges...
Here's the latest:
I got the bid from the York contractor, $1500 to $2000 more than the lowest Trane bids, so far. What I did not like was the warranty of Parts 5 years & labor 1 year. And I don't think I want start getting into York part, etc. My head is going to explode...

The Trane bids are getting more similar to each other. I have given up on anyone doing anything close to a Manual J. All stick to the 5 ton size of what I already have. They will drop from my current 162Kbtu gas furnace to a 120Kbtu 2-stage furnace with variable fan. Half want to just flush the lineset; other half say best to replace, to be sure. And I think the coil is a larger 24" unit, to handle the 5 ton condenser.

The model numbers are:
XLi51 Condenser: 4TTX5060
XV80 80% Furnace-2 stage, Var Spd: TUD120R9V5K
Coil: 4TXCDO61-(which I think is the 4TXCD061BC3HCA-24.6")
T-stat: Honeywell Vis Pro8320
Lineset: replace.
$8500.

I have found one contractor highly rated in the Checkbook mag that looks good and this price is about as good as I might find. I want to checkout a couple more contractors to be sure.

What do you think??? Gary
P.S. Why are gas water heaters so expensive to replace?: $1120.

Good setup. I would get a media air cleaner to protect the equipment and provide better filtration if it can fit into the budget. You could call the guy and tell him you're ready to sign right now if he'll throw in the media air cleaner. They aren't that expensive (relative to the rest of the equipment). Also, I would request the Trane TCONT802 thermostat--same thing as the VP 8320 but it is Trane branded (not a huge thing but I like the Trane thermostat for Trane replacements). One last thing: ask for the 4TXCD064BC3HCA (12.00 EER, 14.50 SEER) coil rather than the 4TXCD061BC3HCA coil (11.80 EER, 14.25 SEER). You will get closer to 5 tons of cooling, which may or may not be a good thing depending on how much cooling your home really needs according to a load calc (56,500 BTU's vs. 55,000 BTU's). Good luck with the new system. No clue about gas water heaters...

ryanhughes...
I currently have a Honeywell electronic unit that stopped working so I am going to keep it and just put in the 5" Honeywell media filters.

I tried to do some checking on the 4TXCD061BC3HCA coil vs. the 4TXCD064BC3HCA that you recommend. Trying to understand the difference. I see that my coil no. is '61' where your recommendation has a '64' ('nominal capacity in 000's BTUs'). The only other specs that change seem to be the 'Rows / F.P.I.' (what is this?); they would increase from '3/14' to '3/18'. Not sure what this differences mean in performance.

And I see the 'CFM vs Pressure Drop across coil' for your recommendation is lower for each Pressure Drop point.

Did you choose this because with the slower CFMs will be better for de-humidification??? How will the lower CFMs affect the heating cycles, if it does???

Gee whiz...this is interesting! Not sure if I am asking the right questions but I hope you get my drift.

I tried to use the ARI site to see if I could come up with your EER and SEER rating but I just don't understand what I need to input to make it work.
Thanks... Gary

ARI can be tricky until you get the hang of it. Go here: http://www.ahridirectory.org/ahriDirectory/pages/ac/defaultSearch.aspx and put in the following: 4TTX5060 (outdoor), 4TXCD (indoor) and *UD120 (furnace). Entering all of the model number isn't always necessary, and the T is omitted from the furnace model number I assume because American Standard and Trane use virtually the same furnace and that can be an "A" or a "T." I think the rows / F.P.I. indicates the number of coil rows and fins per each inch of the coil. So in this case, I guess the 064 transfers heat a bit better, thus the more capacity and more efficiency (this is just my speculation). I chose this coil because the width is the same and for a bit more efficiency it seems like a good decision. However, for some reason, ARI lists the 061 as having a lower operating cost. I'd take the higher efficiency numbers from the 064. Hope this clears things up a bit.

ryanhughes...
Yes, that is the site I was trying to use. Thanks for giving me the correct inputs. Pretty cool!

It is interesting that the '64' has a higher EER and SEER but its operating costs for cooling are higher (not much).

Just had yet another contractor give me a bid today. He will be emailing it to me tomorrow or so. But he raised a couple points. He said they will change the exhaust line to a double wall pipe to make it more efficient--keeps the gases hotter for better venting. No one else mentioned this.

He also said he would put in a new lineset. His data says it should be 1 1/8" as opposed to 7/8". I asked him to doublecheck this but he gave me a look that he has done this many times. After he left, I found the Trane specs (for a 5 ton) that state the 1 1/8" is for R22 and the 7/8" is for the R410, which I will be getting. I wish I had pointed this out when he was here. I'll wait to see what his final bid says.

Thanks much for your help. I am really learning a lot.
Gary

Goddi,

See the attached link below as it lays out all the lineset sizes for the XLi family of straight-cool condensers. 1-1/8 suction for 5 ton and 7/8 suction for 4 ton (4TTX5).

Here is a link that might be useful: Trane XLi TTX Catalog Page

ryanhughes...
Yes, that is exactly what the last contractor showed me when he said the lineset should be 1 1/8".
But, if you look at this PDF below, and look at the '61' and '64 5 ton unit, it says the R410 requires 1 1/8"; R22 requires 1/8".
How do I resolve this apparent contradiction...if there is one??????
http://gotrane.com/CPS/uploads/userfiles/dxunitarysystems/split%20systems/coils/22-1813-02_12012007.pdf
Gary

ryanhuges...
I just noticed that the PDF I just mentioned says it is for "heat pumps/cooling comfort coils". Does this mean the specs are ONLY for heat pumps and I should not be using it for the lineset specs for my system???
Gary

That looks like the right coil. It does mention "* Reducer supplied with R-410A models" to make the transition to the coil sweat connection.

ryanhughes...
But what do you think about the lineset size question??? Is there a contradiction in the recomendations by Trane for the size of the lineset for R410???
Gary

I understand what you're saying. I think it's merely the fact that the connection for the coil is 7/8 and the connection for the outdoor unit is 1-1/8. You'll have to ask your contractor. I think I'd go with the 1-1/8 lineset. The coil document you provided did specify that a reducer is supplied, so I guess Trane knows about the smaller connector on the coil. I don't know why this is, but I'm sure your contractor can tell you why.

ryanhughes...
Ok...I see what you mean about the reducer. I didn't get it at first. But is seems strange that they would restrict the flow at that point with a reducer. Interesting. I just put the same question up on HVAC-Talk to see what others might say.
Thanks much for your help. I'm waiting on more bids but getting close to understanding all the parameters in this process. Gary

ryanhuges...
I just got this from one contractor when I questioned the size of the lineset. First time I got a straight and clear answer from one of the HVAC contractors. Super! Surprising how so many other contractors want to keep the 7/8" line for this same setup...

"You need a 1 1/8" x 3/8" line set for this equipment. You go by the outdoor unit specifications which state 1 1/8". You don't go by the coil connection size which is 7/8". You run 1 1/8" from the a/c unit up to the coil and reduce it to 7/8"."

Gary

I agree with the contractor. I would go by the outdoor unit dimensions myself. Better than being undersized IMO. Good luck.

hmm ive lost my life reading this much info ,especially from non professional giving each other a lot of information gained from the internet..

However IF you had a 5ton system that worked ok but you have changed the overall infiltration and heat loss and gain with all the sealing up of gaps,better E-windows and doors and more insulation then you have changed the dynamics of the system,man J or no manual J, it is obvious.

If i was installing this system id be putting in a 4ton two stage/two speed outdoor 14/16 seer 410a condensing unit,a two stage 80% VS furnace if you are in the southwest/west/south or if you are in the north or north east then a 90% or higher two stage variable speed 5 ton drive furnace with a 5 ton evaporator coil with TXV valve.This way your ducts and airflow can be adjusted with the 5ton drive to meet a 4ton or higher air flow and the VS motor will help with any mistakes made in the design as long as they are minor.The 5ton coil will help remove moisture faster with the larger surface area and be in tune with the furnace.

I definitly would go with a media type filter and make sure all the ducts get properly sealed on both ends as well as entire system at all attachment points.

I would also recommend ,IF this isnt already done,zoning the single system to at the very least a two zone system seperating the upstairs from the downstiars and using two thermostats in key areas to better fine tune your comfort. the humidistats can be set for proper humidity control and cooling so again this will help the system run as long or short as neccessary to get to your comfort level.

also in closing IF you are going from 22 to 410a i would definitly change the lineset as if the flush isnt done correctly or any trace remains in the lines at all ,even a minute trace it will slowly kill the inside of your compressor and eventually with a few years ruin the new system.Its not worth the risk IMO,so if you are spending this kind of money already what an extra 500-1k to protect your investment?

I am a licensed contractor in the USA but will remain anonymous for liability reasons.

good luck

Hi Ryanhughes...
While I am still digesting all this information, I came across a site that does a free online Manual J that is more complex than most. Check this out and see if it is worth doing. I took a look at it but my eye glazed over after a while. The first question of "number of rooms" is not clear... Do they want bedrooms or 'major' rooms? Excluding bathrooms?? duno. I give up. I have all the information but I just am not sure how to input it correctly. Anyway, I thought you and others might be interested in this site. None of the contractors I've dealth with will do a real Manual J so it is still a guessimate.

http://www.acdirect.com/new_faq/faqs.php?gclid=CNHn7cLJjpUCFRKLxwody1etfw

Gary

Not sure if I'd trust a "free online Manual J." Best to do a Manual J with floor plans in front of you or on site. I wouldn't gamble your system's proper sizing based on an online site. I recommend you look into HVAC-Calc (www.hvaccalc.com).

This is a very interesting thread. This is why I offer free consulting when performing a Manual J and Manual D. Load calcs are a standard to measure by; if your not measuring your guessing It is very hard to find an HVAC contractor who will do a Manual J or Manual D, but then show and explain its benefits for the home owner. Investments on a Hvac system can be as much or more than a vehicle. goddi, I give you an A for effort and determination on wanting to get your answers before you investing your dollars. lol David

Here is a link that might be useful: ACCA APPROVED HVAC LOAD CALCULATIONS

Hi Gary,
For the benefit of this online community would you mind posting the exciting conclusion to your HVAC saga? I feel like I've just read a good book only to discover the last chapter is missing! What decision did you you ultimately make and looking back, do you think the manual-J from HVAC-calc was valid for your home? Thanks, Brian