Help! Got three different load calculations, from 3 to 5 ton!

[phillygal]

I am so frustrated - and so hot! We really need to replace our air conditioner,
and will probably be getting a heat pump, since we presently have expensive
electric baseboard heating. This is our problem: we got three estimates;
one from a company that has serviced our 32 year old Trane for many years;
one from Sears (my sister got her new system from them), and one from a
company that was recommended by three families. Okay, they each measured,
asked questions, and came up with a system and price (I know two of them
did not use Manual J - I don't know about the third one.) Here is the dilemma -
the company that we have been dealing with for many years said we needed a
3 ton unit (reasonable for 2000 sq. ft?), Sears said 3 1/2 ton, and the company recommended by three families said 5 ton! I know it's not necessary, but I would like to find out how many tons my old unit is, just for comparison. I'm not sure whom to trust - I even went on Consumer Reports website and used their load calculation tool for individual room air conditioners
( http://www.consumerreports.org:80/cro/appliances/air-conditioners/reports/sizing-worksheet/index.htm), and came up with 3.8 ton, not including my bathrooms! Should I just find two other contractors to get estimates from, and
make sure they use Manual J? Any help would be greatly appreciated.

[desiray]

I am not an expert, but 2 estimates that I received on a 1500 sq. ft.ranch house, taking into account amount of glass,vexposure of windows, and btu's came up with a 3 ton system. The 3rd estimate was a 2-1/2 ton. This makes it seem like the 5 ton would be a bit big.

[mayguy]

First of all, Don't even bother with the room A/C sizing.. That's just for one room. not whole house.

Above below the ad banner, there is a tab HVAC Calc. You can down load a home owner's version for $50.

3 ish range sounds about right. 5 it out of range.

I am in MN, and my home is 1700 sq ft. and I have 2 tons. no problem.

[RoBoTeq]

I'm usually good with frustrated, hot women but since a 3 ton system in your 2,000 square foot home would be 666.666 square feet per ton, I am a little aprehensive to get involved :D

Without doing a proper load calc, there really is no postitive way to know what your home would be best with. A three ton system in a standard type of home with basic insulation and a normal amount of low-leakage windows is about the norm for the Philly area though.

What is the model number of your existing unit?

[uktra]

Pay to have an independant energy auditor/rater do a load calc. Make sure that person performs a blower door test to check for air infiltration rate (every body else is just guessing-usually wrong). This will give an accurate size answer for you, and do not buy larger. Doing this will be worth the cost--you will probably end up buying a smaller unit that costs less per month to run.

[hackmaster]

Find out what what capacity you have right now..3 or 3 and half ton and stick with that if for all these years the existing system cooled your home as you wanted. Its common sense and really no heat load calc is necessary in this instance although I usually do one anyway just to keep up with the ways of the world. If you have a existing 3 ton which has cooled effectively all these years and some company tries to move a 5 ton on you then show them the door...and thats no matter what his manual j says.

[phillygal]

RoBoTeq,
The model number of the Trane unit we now have is raub3520.
As I said, it is 32 years old. Thanks for any help.

[Toolpusher]

Originally posted by hackmaster
. Its common sense and really no heat load calc is necessary in this instance although I usually do one anyway just to keep up with the ways of the world.

You can check the units data sheets,
some if matched right, can out perform a 1/2 ton bigger lesser seer unit.

I was up against a bid that wanted to sell a 3 ton unit,
By my figures it only called for a 21/2 ton. He questioned my numbers since I was a smaller sized unit.

I showed him what he had now, which was a 3ton. and showed him what a 21/2 ton 13 seer match with the right coil and his indoor unit would produce almost the same cooling btu's as his 3 ton unit he was about to replace.

I ran into them in public one day, they both said how happy they were they went with my suggestion.
Their bills are less, and they have told others .

[wolfstrike]

1) probably going to need the 5 ton.

2) don't buy anything from Sears

[comfortdoc]

Feel free to contact me. I will be happy to walk through the house with you and discuss the aspects of system sizing and all the factors that contribute to properly sizing a system. One of the largest factors in our Philadelphia homes is existing duct sizing. It must be considered.

I will measure your house and input the data in HVAC-Calc right then. You will have a proper manual-J before leaving.

[dan sw fl]

Originally posted by comfortdoc
I will be happy to walk through the house with you and discuss the aspects of system sizing and all the factors that contribute to properly sizing a system. One of the largest factors in our Philadelphia homes is existing duct sizing. It must be considered.

I will measure your house and input the data in HVAC-Calc right then. You will have a proper manual-J before leaving.

Why don't you just ask for a phone number & date?

Blower door test and site review is a good route to
validating few Manual J assumptions.

[billb7581]

Philly Area here, 3 Ton unit (with mismatched coil even) seems to do the job for me (1900 sq feet)

[cem-bsee]

even 3 tons should be too big, if one spends some $ on insulating and sealing! I cool 2133sf of trilevel with 5000btu/h [0.42T] -- in Huntsville AL -- sure a lot hotter than Phila --
using ___ton/sf is little better than using 1T/finger when standing across the street & seeing how many fingers it takes to hide the house profile!

[coolmen]

5 tons/2000 sq in phila. must be the poorest built house around. do the load calcu above for 50.00. its very easy cause I use it every single day. let us know what you came up with.

[RoBoTeq]

Energy auditors, blower door tests, load calcs....oh my!

Geez, do you guys like to complicate things.

That existing Trane looks like a 3 tonner. A new 3 ton system will most likely be a little less on functional capacity, but that is not necessarily a bad thing.

If your existing system did the job of cooling the home and cycled off periodically, do not put in anything larger.

[coordinatesales]

If your house where here in OK, 2000 sq ft would usually be a 4 ton. I can't imagine it being 5 ton where you are at. 3 tons sounds about right for your area. Around here, I wouldn't trust Sears as far as I can throw 'em.

[craig001]

I experiencing the same thing, but only two different sizes in my case. The rep whose company I will probably use told me the same thing RoBoTeq said about the house being comfortable with the current unit then replace it with something close.

As far as Sears goes, they were the highest bid for by over ~$4k for a Carrier Infinity set-up and would not match the bid that used the same equipment. Then the rep no-showed without a call when she was supposed to come out a measure for a Heat Gain/Loss calc. I have a feeling she was told not to come because I was being a pain about their adverised policy of price-matching and they probably didn't want to reduce their bid by the difference plus the 10%. I would have stuck with them if they would have just matched to other guys price since they were the first bid and their contractor rep who came out to survey the job seemed to be knowledgable.

[gas1]

the 3 will work if the old unit is a 3 . dont oversize it
put in more insultion it will help summer and winter

[macgivor]

Dear Phillygal, glad to see that you have many responses;
a main factor is called design temp, and this is usually based
on an outdoor temp of 95 degrees. This means that when the
outdoor temp is 95, the indoor temp can be brought down to 73-75 (assuming humidity and other factors are within norm).
This all adds-up to say that a 2 ton unit will cool your place if the oudoor temp and humidity are not too high; on the other hand, if you have a party in july with 50 people and outdoor temp & humidity of 97 & 97, then you will sure appreciate a 4 or 4 1/2 ton unit. So, what is normal or what is best is sometimes based on what you expect. If you want to be
a polar bear when it is 95 and rising outdoors, go for the 4 ton but you will not get great humidity reduction when temps are 80 -90 outdoors because a big unit cools great but runs in short cycles. If you want great humidity control, go for the 3 ton, but you will not get great cool with a party of 50 in july. Sounds like 3 1/2 ton might be you best of both; Get the idea?
I also live and work in Philly. Be glad to here you response. Sincerely, Macgivor.

[leapfrog]

Originally posted by hackmaster
really no heat load calc is necessary in this instance although I usually do one anyway just to keep up with the ways of the world.Which would be a good thing, since many original installations are oversized.

http://www.fsec.ucf.edu/Bldg/pubs/ACsize/index.htm

[twisterbret]

Originally posted by RoBoTeq


That existing Trane looks like a 3 tonner. A new 3 ton system will most likely be a little less on functional capacity, but that is not necessarily a bad thing.

[/B]

Newer 3 ton units arn't as powerfull as old ones? I'm looking to replace my 3 ton 30 year old AC with a new 3 ton. See What's my AC thread.

Thanks!

[RoBoTeq]

Originally posted by twisterbret

Originally posted by RoBoTeq


That existing Trane looks like a 3 tonner. A new 3 ton system will most likely be a little less on functional capacity, but that is not necessarily a bad thing.



Newer 3 ton units arn't as powerfull as old ones? I'm looking to replace my 3 ton 30 year old AC with a new 3 ton. See What's my AC thread.

Thanks! [/B]

Changing actual sizes of stuff as to what we call it is not a new thing. Just try to find a 2X4 that is actually 2"X4" :D

[dan sw fl]

Originally posted by leapfrog

Originally posted by hackmaster
really no heat load calc is necessary in this instance although I usually do one anyway just to keep up with the ways of the world.Which would be a good thing, since many original installations are oversized.

http://www.fsec.ucf.edu/Bldg/pubs/ACsize/index.htm

The article in your link is Really Out-dated regarding
the latest Florida _requirements_ for equipment & duct sizing/design and new residential construction permitting.

" M1401.3 Sizing.
Heating and cooling equipment shall be sized based on building loads calculated in accordance with ACCA Manual J or other approved heating and cooling calculation methodologies. "

" M1601.1 Duct design.
Duct systems serving heating, cooling and ventilation equipment shall be fabricated in accordance with the provisions of this section and ACCA Manual D or other approved methods."

http://infosolutions.com/icce/gateway.dll?f=templates&fn=default.htm&vid=icc:florida_residential

[xv80satisfiedcust]

The best thing about HVAC calc is you the homeowner can see how dramatic of an effect any FUTURE insulation, windows etc.... can lower your CONSUMPTION.

So, you get a 3 ton that's barely big enough today (if that's what HVAC calc tells you). 3 years from now you finally have the money to do the insulating. Better to have the right size for the future than oversize today.

[phillygal]

Thank you all so much for your helpful replies to my original post!
Since humidity control and efficiency are more important to us than temperature control, we have decided to go with the 3 ton Carrier Performance Series Heat Pump, and will most likely use the local company that has serviced our old machine for many years. They have been in business for over 50 years, with no BBB complaints. I think their price is fair, but a bit above the other estimates I got. I'm thinking that since they are local and familiar with us, we will probably have a prompt response from them with a service request. Hope so.

If I may pose another question or two - is there a rule of thumb for number of registers needed in a particular room? The reason I ask is that
we have only one register in our den on the first floor, and one register in
the bedroom above the den. These rooms are both on the East side of
the house, and although the den is very cool and comfortable in the summer
the bedroom is not, especially in the morning. Would you suggest a second
register be installed in the bedroom (I think it shouldn't be too complicated, because the unit is right above the bedroom in the attic). We also have only one return duct, in the ceiing of the hallway on the second floor. For 2200 sq. feet, should we have another one? Last question - my husband and I and our two kids all sleep with our bedroom doors closed. As I said we only have one return duct in the hallway. Do we need to leave the bedroom doors open at night to get the best results from our heat pump, both winter and summer. I will also ask our contractor these questions, but thought I would use your expertise. Thanks.

[leapfrog]

There are no 'rules of thumb' for the number or size of registers. Ductwork is designed using ACCA's Manual D or equivalent.

Consider having your contractor do a Manual D and then also add return ducts and registers rather than the single return you have now.

[phillygal]

After considering all your helpful replies we have decided to go with a
3 ton unit. However in reviewing the estimates we noticed that the estimate
for the 5 ton unit was substantially less than the 3 or 3.5 ton unit. It is a
Lennox whereas the 3 and 3.5 ton units are Carrier. We understand the quality
is comparable? Does anyone know if Lennox is generally cheaper than
Carrier or if any other brand of equal quality is substantially cheaper?
Thanks for any help.

[hackmaster]

Stick with the 3 ton and you will be quite happy. You dont want to oversize with the 5...your gonna end up with foggy windows and some humidity issues.

[danglerb]

Some brands I have looked at must have at least half a dozen levels of quality, from low low end builder units, to top of line don't ask the price units. You can't compare brand to brand, you have to compare model to model. I am shopping 3 ton for myself, and the price range from the cheapest to the most expensive is about 4:1, and that isn't even comparing no frills to full featured (I require a "nice" variable speed 2 stage furnace), its a question of efficiency and brand "mostly".

Some brands do add to the price just for the "name", and some are worth it, and others need the money for advertising.

Seer affects the cost the most, with a big increases from 13 to 15, and again with 2 stage compressors and 15+.

I've narrowed my own search down to two different systems, a Bryant close to 16 seer that meets the tier2 energystar requirements for about a $350 tax credit, and a midrange York that is barely 14 seer, but a bit less than 70% of the Bryant cost. Both systems will use nice 2 stage variable speed furnaces, differences are brand, seer, rebates, and warranty (but I may be able to actually get a better warranty on the York at modest additional cost to existing bid). Both contractors have been around with fine BBB records for 20+ years, but one is small family owned, and the other larger with several crews. Plus and minus for each choice. ;)

Final note, the York system initially bid out even less, but Bryant includes stuff that I want and had to add to the York, like a nice filter box, and a extended service contract (Bryant had 5 yrs on whole system parts and labor).