Houston: 3.5 tons for 5,200 sq ft house?

[dash]

Note that I said new construction,and allowed that errors acn and have been made.Existing are more difficult ,so you have to be careful and if you are not sure error on the side of caution.

Garbage in = garbage out,but when the input is proper I've never had a problem.


Who decides if it's undersized?The design documents,does it maintain X° in the home,at X° outdoors,yes or no,period.Yes we have had people say it runs too long,doesn't handle 20 people at parties,etc, etc..That is not the question in this thread.



[Edited by dash on 06-30-2005 at 11:32 PM]

[trane]

Originally posted by uktra
Trane--How many homes have you designed that you guaranteed HVAC monthly costs, humidity levels, and temps no more than 3 degrees room to room?

None, My customers don't require it. But I do guarantee they will be happy with their new system. I can also guarantee they will be cool on the fourth of July and warm on Jan first. Is that also in your guarantee? How many on this site size all the residental equipment themselves (ALL) now how many have had to follow specs that a engineer had came up with on a commercial job and new it wouldn't work? I put in 91 split systems in 1994 that were sized by a engineer using manual J and told them before we started (in december and it was cold) that they would not work. They waited until 13 were installed before they believed me and paid to send all of them back and exchange them for bigger equipment. They also paid me to take out the first 13 and I might add it was your tax dollars paying for all this.

[trane]

[QUOTE]Originally posted by dash
[B]Note that I said new construction,and allowed that errors acn and have been made.Existing are more difficult ,so you have to be careful and if you are not sure error on the side of caution.

Garbage in = garbage out,but when the input is proper I've never had a problem.


Who decides if it's undersized?The design documents,does it maintain X° in the home,at X° outdoors,yes or no,period.Yes we have had people say it runs too long,doesn't handle 20 people at parties,etc, etc..That is not the question in this thread.

What was the question, something about a fake house right? Look at what he started.

[uktra]

Trane--thats a great story, but it doesn't prove manual J is wrong--it only proves the engineers screwed up. The reason I am so confident in manual J is that I also design the thermal envelope of the home with the ducts inside conditioned space. This frees up the 25% over capacity designed into Manual J for things like leaky ducts and leaky homes.

Customer might not demand guaranteed HVAC monthly cost, humidity levels, and even temperatures in the home, but Building America homes provide this at NO EXTRA COST and poeple want it. Sales figures have proven it.

[Edited by uktra on 06-30-2005 at 11:56 PM]

[trane]

Originally posted by uktra
Trane--thats a great story, but it doesn't prove manual J is wrong--it only proves the engineers screwed up. The reason I am so confident in manual J is that I also design the thermal envelope of the home with the ducts inside conditioned space. This frees up the 25% over capacity designed into Manual J for things like leaky ducts and leaky homes.

Don't get me wrong, I have no doubt that the new houses you design can be sized with manual J and be conditioned with smaller equipment than most would think. These are not the average home and the average home owners. I was only trying to say that manual J has to be used with common sense. Got to go but its been interesting.

[uktra]

No one said manual J doesn't need to be used with common sense, or not done correctly. Manual J will work on average homes and average people if done correctly. I have a problem with people like mrbillpro and classical who say manual J won't work in Houston. It will and does.

[Mr Bill]

Originally posted by uktra
I have a problem with people like mrbillpro and classical who say manual J won't work in Houston. It will and does.

Go back and re-read these posts I never said it "would not work" and I also said you need to use some common sense I am sorry either you misread my posts or did not quite understand.

This is what I said below:

Heat load, Manual J,manual D whatever heat load you use to calc. you will be warm in a home.

the hell with all that manual J and D in Houston you will not be comfortable with a 3.5 ton on 5200 sq .ft.

By the way did old J&D put common sense out of business? if so were all in deep po-po.




mrbillpro:
Well, in my personal opinion being in the a/c business for over 27 years in Houston trust me you will never cool a 5,200 SF home in Houston, Tx. with 3.5 tons of air unless it's 3.5 tons of ice you have poured on top of your home. Heat load, Manual J,manual D whatever heat load you use to calc. you will be warm in a home that big here with that little a/c I can promise you that.


mrbillpro:
I don't have read anything you install a 3.5 ton in Houston on 5200 sq .ft. and unless you building it in a cave you won't be comfortable, and I could care less what really anyone thinks I just want the address when you get er" done so I can go by and check out how happy the customer is, that is called proof the hell with all that manual J and D in Houston you will not be comfortable with a 3.5 ton on 5200 sq .ft. unless you have no glass and use R-600 insulation and your inside a cave I work around this everyday in Houston but hey you know better than me go for it!


mrbillpro:
If I have bought a 5200 sq. ft. home my guess would be, either a lot of occupants or a lot of parties call it abnormal conditions may be perfectly normal to some and you brought up a good point as to why you can't totally rely on old J & D.

By the way did old J&D put common sense out of business? if so were all in deep po-po.

[dash]

Aren't "you won't be comfortabe" and "won't work" the same thing?


What has Man D ,have to do with this?Are you saying Houston requires "rule of thumb" duct design or some special duct design ,other then Man. J?

[uktra]

Oh now you claim it will work? which is it you can't have it both ways.

[Mr Bill]

Originally posted by dash
Aren't "you won't be comfortabe" and "won't work" the same thing?


What has Man D ,have to do with this?Are you saying Houston requires "rule of thumb" duct design or some special duct design ,other then Man. J?

You know dash this argument is none of you dam business, why are you in this if you have a beef with me come to Houston and we can work our problems out otherwise let me and ultra work this out.


Aren't "you won't be comfortabe" and "won't work" the same thing?

and no this is not the same thing in my books.

[Mr Bill]

ultra, I am trying to work with you here to learn if about your product and like I said before, I will get out to one of these homes to check it out soon and if I see it does work an apology will be in order and if I get a lot of bad feedback that will be posted also so can we be men about it until I get a chance to check it out in the real world? if not helping you reputation or mine by being behinds about it, and now we have others involved in "OUR" disagreement which is "not" helping anything but kids will be kids.

[dash]

If you only want one person to comment,I suggest you use email,instead of a public forum.

[Mr Bill]

Originally posted by dash
If you only want one person to comment,I suggest you use email,instead of a public forum.

Thanks, I will take that advise.

[uktra]

Dash--trying to get the HVAC industry out of the "dark ages" is a full time job, isn't it?

[Mr Bill]

Originally posted by uktra
Dash--trying to get the HVAC industry out of the "dark ages" is a full time job, isn't it?

Do you really think posts like this help you integrity? With comments like this I am now personally even more skeptical about your product, but I will give you the benefit of the doubt by checking out one of these homes, I hope your sale pitch has a better attitude with the public than here because I will be glad to print your posts and let the new prospective HO read the kind of attitudes the folks that design these homes have.

[uktra]

Mrbillpro-I sincerely apologize for my weak attempt at humor, but let me tell you about a phone call I just had from a friend. She had seven HVAC companies come out to her home to replace an operating old gas boiler, with a new higher efficiency unit. Of the seven companies that came she received only 3 written bids. I helped improve her home many years ago and did a load analysis of 62k btu/h. All of the companies wanted to put in 100 to 120 k btu/h units and no one did a load analysis.

I can tell you that people are becoming more intellegent about decisions of this nature, and that is why I have work. People paying big money for new homes want energy effeciency, good air quality and comfort. The homes you need to visit proves this because they sell faster and have fewer callbacks than code built homes. You can question my integrity all you want to, that is your privilege. I only am concerned with what my clients think.

[pstu]

It would not be bad if people would address the question the way Panama asked in his original post. Some of these valid points which have surfaced, would have been appropriate on the first page. The ways in which human behavior might frustrate the goals of Manual J sizing, is a valid one. If the average homeowner needs over-capacity some way, that is good for the rest of us to know. If the average installer gets something wrong in a way that reduces capacity, that is good for (at least us homeowners) to know. And it would be great to learn about the things with an existing house vs. new construction, which make it trickier to get OK performance.

In my own case (one 1989 house) I think I am collecting empirical evidence that more capacity is needed than Manual J says, and the reason could very well be the ductwork in this house. Or other things that I don't know so far. The existing size is 7.0 tons, a whole-house Manual J is 4.5-5.0. One HVAC guy prescribed 9.0 tons, he is not a hack but rather an old fashioned craftsman, but his main method appeared to be sizing airflow room-by-room based on experience, and then calculating what tonnage is appropriate to that total airflow. My experiments with duty cycle appear to tell me one unit can be downsized by 0.5-1.0 ton, the other unit probably not. In this case I think it will be prudent to pay up for a pro to do the room-by-room Manual J before committing to a new size. The best results won't be obtained by a DIY method, I am sure you will agree.

Best of luck all -- P.Student

[Edited by perpetual_student on 07-01-2005 at 11:28 AM]

[pstu]

If MrBillPro ever gets to visit one of these houses in question, and can tell us why or how Manual J fails to be comfortable, I will regard that as excellent information. I know he's pissed at what I said and that is regrettable. We need to work with peoples' skills as they have, any clue that is contradictory to the Manual J plan would be fine. Maybe the customers of MrBillPro tend to have children running in and out, or want fast cool-down even with the compromises in humidity control etc. which are supposed to happen when you oversize. If anyone can oversize without these disadvantages (perhaps the way Airman designs) it is interesting to hear all the details.


Best of luck all -- P.Student

[Edited by perpetual_student on 07-01-2005 at 11:27 AM]

[pstu]

Apologies to the board for the duplicate posting. The board software is giving me inappropriate messages, this is a case where the error message itself is wrong. At this time I cannot succeed in deleting my own message, or editing it.

Regards -- P.Student

P.S. And then I *could* edit my posts. Computers, aren't they wonderful?

[Edited by perpetual_student on 07-01-2005 at 11:29 AM]

[teddy bear]

It's safe to bet the readers of this subject is down to the hard core posters.
The better the home is designed/built, the lower the sensible, the higher the latent heat ratio needed to provide comfort. There are also are many hours of the year with no sensible cooling load and significant latent load. Also the loads from the occupants vary, single occupant to a "party". In the a/c industry, we hide behind "it's oversized" when people complain about high humidity. Perfectly sized sensible/latent loads for a typical home varies from 100% sensible/0% latent to 0%sensible/100% latent. If we size the a/c properly, we can handle this load right? Here's how far we have come. We offer 70%S/30%L simple single speed, maybe twecked to 65%/30% @ 50%RH. Nexted for a premium price and complexity, we 2 speed the a/c. Max latent also overcooling to remove more moisture.

Soon to be release is partial reheat with a 20% S/80% L meaning overcooling at a lower rate. The reheat feature will be added to the 2 speed a/c with an additional level of complexity and cost. Adding an additional le complex, extremely expensive and energy inefficient, none of these systems are able to provide 0% S/ 100% L. The "gold standard" for humidity control is a simple adequately sized a/c for the max sensible load and high efficiency whole house dehumidifier. This combination provides <50%RH with a 90^F-70^F inside t-stat settings without any cooling load. With normal margins, the retail is 2-3 thousand more than a/c only. The mechanics are as simple as the a/c. Thanks for the future comments. TB