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Estimator didn't do a load calculation, just looked at size of existing unit

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Estimator didn't do a load calculation, just looked at size of existing unit RAJ 06-12-2006
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Posted by Chris Hill on June 15, 2006, 10:28 am
wrote:
>
>RAJ, why do you care about seeing the actual calculations? If the end
>result is that you need a furnace of XXXBTU, what difference does it
>make how he got to that conclusion (or are you supposed to verify his
>work?). If you were looking for more quotes you would then use the end
>result to ensure that the other guys aren't off the mark, right?

I'd care because unless I see them I won't know if anything was
actually calculated. Last time I had the job done none of the three
guys I called calculated anything.

Posted by DK on June 15, 2006, 10:53 am

>I guess the best way is to just get the estimat first, then say you'll
>sign it only if they do the load calculation. The estimate will
>probably be overpriced anyway, so might as well get something extra out
>of it.
>
>Chris Hill wrote:
>>
>> >He just asked me if the existing system cooled properly. Is this
>> >acceptable?
>> >How would a different sized system effect the existing ductwork though?
>>
>> If you bought a higher efficiency system, you may need larger ducts
>> because I believe they need to push more air. That's what I've read
>> anyway. Don't feel bad, last time I had mine replaced I called three
>> people and none did a load calc. Next time I think I'll offer to pay
>> for the estimate if they'll do one and show their work.

Load Calcs are usually not necessary. Within 5 miles of me, there
are 10,000 homes built by the same 3 builders, each using 5 building
plans. Everyone in the hvac business knows exactly what size unit
these 5 plans require.

The only load calcs necessary are the 7 custom built 7 bedroom homes
that get built each year.

Do all these homes have exactly the same size units for the same
plan?
- No, of course not. Joe and his wife like to run their thermostat
at 60 degrees year around, even in 105 degree spells. Theirs is a 5
ton system while their friends have a 3 1/2 ton system.

All it takes is a brain and talking to your neighbor., not a load
calc - that will probably be inaccurate anyway.

.









Posted by Chris Hill on June 16, 2006, 11:34 am

>
> Load Calcs are usually not necessary. Within 5 miles of me, there
>are 10,000 homes built by the same 3 builders, each using 5 building
>plans. Everyone in the hvac business knows exactly what size unit
>these 5 plans require.
>
> The only load calcs necessary are the 7 custom built 7 bedroom homes
>that get built each year.
>
> Do all these homes have exactly the same size units for the same
>plan?
> - No, of course not. Joe and his wife like to run their thermostat
>at 60 degrees year around, even in 105 degree spells. Theirs is a 5
>ton system while their friends have a 3 1/2 ton system.
>
> All it takes is a brain and talking to your neighbor., not a load
>calc - that will probably be inaccurate anyway.
>
>.
>
>
>
>
>
>
>


Depends on the area in which you live. In a subdivision of new
construction I'd agree. The problem is that once houses get some age
on them they begin to vary. For example, there is one house in my
neighborhood like mine. It has the original windows in it, which are
probably not very efficient. It has the original siding on it as
well. Nobody has even thought to plant trees to shade it and possibly
reduce the cooling load. In about ten years my house won't need near
as much cooling as my neighbor's will.

Posted by STravis on June 17, 2006, 10:52 am

DK wrote:
>
> >I guess the best way is to just get the estimat first, then say you'll
> >sign it only if they do the load calculation. The estimate will
> >probably be overpriced anyway, so might as well get something extra out
> >of it.
> >
> >Chris Hill wrote:
> >>
> >> >He just asked me if the existing system cooled properly. Is this
> >> >acceptable?
> >> >How would a different sized system effect the existing ductwork though?
> >>
> >> If you bought a higher efficiency system, you may need larger ducts
> >> because I believe they need to push more air. That's what I've read
> >> anyway. Don't feel bad, last time I had mine replaced I called three
> >> people and none did a load calc. Next time I think I'll offer to pay
> >> for the estimate if they'll do one and show their work.
>
> Load Calcs are usually not necessary. Within 5 miles of me, there
> are 10,000 homes built by the same 3 builders, each using 5 building
> plans. Everyone in the hvac business knows exactly what size unit
> these 5 plans require.

Very good info right there. In fact all the HVAC companies that have
given me estimates on my new estimate (except the one guy) all sized
furnaces in the same BTU range based on square footage of the house and
existing duct work. These guys know what these homes are like and what
it takes to heat/cool them. Yes, they could spend 30 minutes or more
doing a load calc but unless they know EXACTLY how the house is built
(wall/window R rating, etc), that information may be innacurate...as
the saying goes "garbage in..garbage out".

> The only load calcs necessary are the 7 custom built 7 bedroom homes
> that get built each year.
>
> Do all these homes have exactly the same size units for the same
> plan?
> - No, of course not. Joe and his wife like to run their thermostat
> at 60 degrees year around, even in 105 degree spells. Theirs is a 5
> ton system while their friends have a 3 1/2 ton system.
>
> All it takes is a brain and talking to your neighbor., not a load
> calc - that will probably be inaccurate anyway.


Posted by STravis on June 17, 2006, 10:53 am

STravis wrote:
> DK wrote:
> >
> > >I guess the best way is to just get the estimat first, then say you'll
> > >sign it only if they do the load calculation. The estimate will
> > >probably be overpriced anyway, so might as well get something extra out
> > >of it.
> > >
> > >Chris Hill wrote:
> > >>
> > >> >He just asked me if the existing system cooled properly. Is this
> > >> >acceptable?
> > >> >How would a different sized system effect the existing ductwork though?
> > >>
> > >> If you bought a higher efficiency system, you may need larger ducts
> > >> because I believe they need to push more air. That's what I've read
> > >> anyway. Don't feel bad, last time I had mine replaced I called three
> > >> people and none did a load calc. Next time I think I'll offer to pay
> > >> for the estimate if they'll do one and show their work.
> >
> > Load Calcs are usually not necessary. Within 5 miles of me, there
> > are 10,000 homes built by the same 3 builders, each using 5 building
> > plans. Everyone in the hvac business knows exactly what size unit
> > these 5 plans require.
>
> Very good info right there. In fact all the HVAC companies that have
> given me estimates on my new estimate (except the one guy) all sized

The above should have read "estimates on my new furnace"...

> furnaces in the same BTU range based on square footage of the house and
> existing duct work. These guys know what these homes are like and what
> it takes to heat/cool them. Yes, they could spend 30 minutes or more
> doing a load calc but unless they know EXACTLY how the house is built
> (wall/window R rating, etc), that information may be innacurate...as
> the saying goes "garbage in..garbage out".
>
> > The only load calcs necessary are the 7 custom built 7 bedroom homes
> > that get built each year.
> >
> > Do all these homes have exactly the same size units for the same
> > plan?
> > - No, of course not. Joe and his wife like to run their thermostat
> > at 60 degrees year around, even in 105 degree spells. Theirs is a 5
> > ton system while their friends have a 3 1/2 ton system.
> >
> > All it takes is a brain and talking to your neighbor., not a load
> > calc - that will probably be inaccurate anyway.


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