Load-Calc????

[Pete924]

I received a faxed copy of my load calc from one of my contractors, what should I look for? It states "Total sensible heat Gain = 30,406 and Total Latent Heat Gain= 5338 and Total Sensible and Latent Heat Gain= 35744" How do you calculate for tonnage, heating?? Is there suppose to be a Total Heat Loss calculation also? where would that be?

[abbottshabit]

Are you doing ac and heat? if so you should get a heat loss and a heat gain. So they only sent you gain (a/c) 35744 gain is a perfect 3 ton a/c or 36000.btu Where do you live?

[Pete924]

I live in Long Island NY, I got quoted for heat & A/C. So I am missing part of it right I need the Heat Loss as well. He says even though its a perfect 3 Ton he would recommend a 3.5 ton due to the R5-R6 Insulation downstairs.

[Don Sleeth]

Pete, relax. If the contractor was good enough to do a load calculation for you, I would suggest you give him a chance to explain it to you. The fact that he did the calc is a good sign, he may be the one to do the best job for you. It is Friday night, relax until Monday and get in touch with him then. I am sure he can explain it all to you then, after all, he took the time and effort to do a load calculation for you, I'm sure he would be pleased to explain it also.

I think you have found yourself a good contractor, you are 95% there to a great system. Enjoy your weekend.

don

[Pete924]

Don, I am relaxed the fact that he only gave me a partial load calc is what upsets me. I asked him for the load calc on what he quoted me, he stated he would fax it to me when I spoke with him over the phone. If he knew that he was only going to fax the A/C part only he should of told me that in the first place during our phone conversation.

Just be straight forward and do what you say your going to do, I've never seen a load calc before so thats why I was curious. I gave him the benefit of the doubt and when I finally get a chance to look it over its incomplete.

Maybe I'm over reacting but thats just the way I feel. I already called and left him a message regarding the rest of it. I was polite and respectful just mentioned that if he was aware that it was incomplete to check the fax in case some pages did not come through and hope to see the rest of it soon.

He is the only one out of 3 contractors to give me at least a partial load-calc, so thats good. Hopefully I will get the rest and he could do the job for me.

[Edited by Pete924 on 10-27-2001 at 02:26 AM]

[arxaw]

Originally posted by Pete924
I live in Long Island NY, I got quoted for heat & A/C. So I am missing part of it right I need the Heat Loss as well. He says even though its a perfect 3 Ton he would recommend a 3.5 ton due to the R5-R6 Insulation downstairs.

Ask for the heat loss calcs for the furnace sizing.

A correct load calc takes insulation R-values into account and the A/C should be sized as closely to the calcs as possible. Since your heat gain is just under 36,000 BTUs or 3 tons, you should insist on a 3-ton unit. This will give you better humidity control.

http://homeenergy.org/archive/hem.dis.anl.gov/eehem/96/960907.html

[DSW Air]

with tonge like that your not relaxing like don asked.get some better insulation for the climate seems has code vialation or is there no min. up there.spend a little now or pay for ever.

[E-Man]

Axraw hit the nail on the head. Those basement r values should already have been accounted for.

[E-Man]

Sorry arxaw, I previonsly spelled ya axraw.

[arxaw]

Originally posted by E-Man
Sorry arxaw, I previonsly spelled ya axraw.

heheh, I've been called much worse... :-)

[Pete924]

"with tonge like that your not relaxing like don asked.get some better insulation for the climate seems has code vialation or is there no min. up there.spend a little now or pay for ever." Quote DSWAir

House was built in 1962, Dormer is 16 yrs old. I guess R5-6 was the norm in NY back then? I cant reinsulate the whole downstairs again.

[Maddog]

Hey Pete, maybe he doesn't want to do all the other guys' work for them.

I don't know how many times I've done a load calc, and sometimes even a duct layout, only to have the homeowner give them to my competition, and then give them the job because they priced it less (maybe because I did the legwork for them!).

[troysp]

Several have said that the Pete should install a 3 ton system as a result of the 35744 BTUH total heat gain result that one of his contractors sent him. Assuming that the sensible and latent loads were correct, wouldn't he be better off basing the sizing of his A/C on the sensible capacity of the equipment that his contracor is proposing. From the numbers that he gave, his sensible gain is 85% of the total. If the equipment that is being proposed has a sensible ratio of less than 85%, and the numbers are correct, he could be undersizing the system. Don has the best advise, talk to the contractor. Find out how he did his calculation. Did he take notes when he visited the job regarding window sizes and numbers? Did he measure the walls? Or did he just ask about the square footage? Most of the contractors I've talked to sized by converting square feet to tons. One who claimed to do a heat load calc didn't even visit the house. He basically converted square feet to BTU's. Not very much difference. So do what Don suggested and talk to your contractor on Monday. If you have time and want even more piece of mind, download the homeowner version of HVAC-Calc for less than $40 and do a heat load calc for yourself. You can even download a demo for free, with fixed weather data, to see how easy the progam is to use.

[Zany]

Troysp..The TOTAL heat gain is 35,477 btuh
There for you need to remove 35,477 btuh to keep up with the heat gain. Latent and sensible heat have both been included in this total. If you were sizing just based on sensible heat, then it would be undersized because latent heat wasn't taken into consideration.
Latent heat is basically humidity. It takes btu's in order to change the state of a gas to a liquid.

[troysp]

Zany,
What I'm saying is that he should size the unit by making sure that it's sensible capacity is large enough for the sensible load and then make sure that the latent capacity of the same unit is large enough for the latent load. Since his sensible to latent ratio is about 85%/15%, if he installed a unit that was right according to the total only and that unit had a sensible to latent ratio of say 70%/30%, he would not have the sensible capacity that he needed. I'm pretty sure that this is the same method followed by manual S. It's also the same advice given by Don Sleeth in the manual for his program.

[Wb2ymc]

Hey Pete:
Sounds like you are almost there. But, remember you must adhere to the LIPA rebate parameters if you want that 14 SEER rebate.
Take the sensible heat gain and divide by 77%. Then add 6,000 BTU (that they will allow) and that is the BTU heat gain they will allow for. Also remember you must not calculate for more than 20 degree differential. Meaning on the A/C side if you are deciding it is 92 degrees outside you cannot calculate as your default any more than 72. But they do give you that 6,000 BTu margin of error.
Unfortunatly, that is the reason that most contractors on Long Island have decided to go 12 SEER because they can't be hassled by this process or they just don't know how to do Manual J and don't want to learn.
It's like I have always said.."it's not that I'm so good. it's 'cause most of my compitition is so bad".
On the heat side if you are going with zoning or BTu modulation or two speed technology you are going to be in the ballpark.
My shop is real busy right now and the location of my business probably couldn't service you well. The jobs I am doing near your home are complicated Hydro-air and/or high velocity jobs, and they are construction type and I would not want to install a system that I could not service 100%.

What we do in muti-story is put a boiler downstairs with a fan coil in the basement next to the boiler. This fan coil has dual coils...one for the a/c and one for the heat. Then I only have to bring two pieces of 3/4 or 1" copper to feed the heating coil in another air handler in the attic. I get two zones, I design the boiler around my heating coils and my a/c around the seer rating I want for the condensers. Therefore there is minimul contruction to get heat upstairs and no boxing in of duct work. The other beauty of this is if the homeowner wants a "in-direct" water storage tank then my boiler can handle that future expansion.Usually what happens is you size for the in-direct and and you put the boiler on "priority" for domestic hot water. These in-direct last forever and have the best recovery rate! Additionally, if you ever wanted to put in radiant heat let's say in your kitchen or baseboard in your basement as a seperate zone you have the boiler as the heart of the system and you are not locked into a warm air furnace. Gas hot water heaters are junk and last for 8-10 years.
This method has become very popular around these parts and knowledgable contractors, builders and saavy homeowner know what it is about.
If you want real hi-tech boilers you can look at "Viessmann" or "Budereus" or even those 90+% direct vent "Munchkins".
The in-direct can be added later or you can get the whole package.
This thinking is not new but more expensive but much more flexible in my opinion and for others who have done it. You gotta "think out of the box".
It doesn't seem to me that your in a super rush to do this job based upon all the questions you are asking and the level of research you have done. You may want to keep on digging.
E-mail me with any questions and I will try to help you.
Brian Gelber

[acme]

Hello Pete. If you are interested you can get a software program online to do your own Load-Calculations. It will cost you $39 for the program and lasts 2 months. I have no affiliation with them, though. Hope it helps. The address is below.

http://www.heat-loss-calculations.com/index.asp