Heating and air conditioning - Heat Calc Discrepancies

Author

Heat Calc Discrepancies

Vic Spainhower

2006-02-13, 3:21 pm

Hello,

I am in the process of getting bids to replace my Trane 2 1/2 ton XV1500
heat pump and the XL1200 air handler which is 14 years old. I've had 2
carrier dealers provide a bid and 2 Trane dealers provide bids. One of the
Trane dealers spent several hours here measuring each room and mapping out
the entire house. He then left and called back and said the heat calc
indicated a 4 ton unit would be required. Each of the other dealers said no
way but none had done a heat calc. The other Trane dealer came out with a
laptop and did the process here and came up and said a 2 1/2 ton is need and
that a 4 ton would create all kinds of problems short cycle etc.

Here's the details:

1. Located in Pacific Northwest
2. 1800 sq feet
3. new Milguard vinyl windows installed throughout 2 years ago
4. Floor, walls - R11 insulation
5. Ceiling R30 insulation

The major difference between the 2 are the floors and infiltration. Both
claim to have used the same parameters!

I'm no expert in heat pumps and I thought bringing in reputable dealers I
would get the straight scoop!

Any advice?

Vic

travlinjohn

2006-02-13, 4:21 pm

If your home is of typical construction, ie no extensive glass or 20 ft
cathedrals, sounds like the 2.5 ton unit is about right. You'd have to have
a mighty unusual home to require 4 tons in 1800 sq. ft. If the second
contractor's figures are correct. Then he is correct in saying you will be
plaqued with proplems with a four ton unit.
"Vic Spainhower" <vic@showsec.com> wrote in message
news:Td6dnW6VBogkT23eRVn-qA@comcast.com...
> Hello,
>
> I am in the process of getting bids to replace my Trane 2 1/2 ton XV1500
> heat pump and the XL1200 air handler which is 14 years old. I've had 2
> carrier dealers provide a bid and 2 Trane dealers provide bids. One of the
> Trane dealers spent several hours here measuring each room and mapping out
> the entire house. He then left and called back and said the heat calc
> indicated a 4 ton unit would be required. Each of the other dealers said
> no way but none had done a heat calc. The other Trane dealer came out with
> a laptop and did the process here and came up and said a 2 1/2 ton is need
> and that a 4 ton would create all kinds of problems short cycle etc.
>
> Here's the details:
>
> 1. Located in Pacific Northwest
> 2. 1800 sq feet
> 3. new Milguard vinyl windows installed throughout 2 years ago
> 4. Floor, walls - R11 insulation
> 5. Ceiling R30 insulation
>
>
> The major difference between the 2 are the floors and infiltration. Both
> claim to have used the same parameters!
>
>
> I'm no expert in heat pumps and I thought bringing in reputable dealers I
> would get the straight scoop!
>
> Any advice?
>
>
> Vic
>
>

Zyp

2006-02-13, 6:21 pm

Your located in the Pacific Northwest? For Heat Pump application in your
area, the HSPF would require a load calculation based on the heating
load.... not the air conditioning load, with the requirements you posted...
my next question would be how did the 'older' unit perform? Did it meet
your expectations? Are you replacing it because you want something more
efficient?

Zyp

"travlinjohn" <jrwmtw@earthlink.net> wrote in message
news:1z5If.1364$UN.80@newsread2.news.pas.earthlink.net...
> If your home is of typical construction, ie no extensive glass or 20 ft
> cathedrals, sounds like the 2.5 ton unit is about right. You'd have to
> have a mighty unusual home to require 4 tons in 1800 sq. ft. If the second
> contractor's figures are correct. Then he is correct in saying you will be
> plaqued with proplems with a four ton unit.
> "Vic Spainhower" <vic@showsec.com> wrote in message
> news:Td6dnW6VBogkT23eRVn-qA@comcast.com...
>
>

udarrell

2006-02-13, 8:21 pm

Vic Spainhower wrote:

>Hello,
>
>I am in the process of getting bids to replace my Trane 2 1/2 ton XV1500
>heat pump and the XL1200 air handler which is 14 years old. I've had 2
>carrier dealers provide a bid and 2 Trane dealers provide bids. One of the
>Trane dealers spent several hours here measuring each room and mapping out
>the entire house. He then left and called back and said the heat calc
>indicated a 4 ton unit would be required. Each of the other dealers said no
>way but none had done a heat calc. The other Trane dealer came out with a
>laptop and did the process here and came up and said a 2 1/2 ton is need and
>that a 4 ton would create all kinds of problems short cycle etc.
>
>Here's the details:
>
>1. Located in Pacific Northwest
>2. 1800 sq feet
>3. new Milguard vinyl windows installed throughout 2 years ago
>4. Floor, walls - R11 insulation
>5. Ceiling R30 insulation
>
>The major difference between the 2 are the floors and infiltration. Both
>claim to have used the same parameters!
>
>I'm no expert in heat pumps and I thought bringing in reputable dealers I
>would get the straight scoop!
>Any advice? Vic
>
>
How did the 2.5 ton heat pump perform?
Did it cool and heat sufficiently?

I would go with the 2.5 ton calc.
You can always do more things to reduce the heat-loss heat-gain
equation! - udarrell
http://www.udarrell.com/proper_cfm_...ng_systems.html

--
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CAVHBC

2006-02-13, 9:21 pm

"Vic Spainhower" <vic@showsec.com> wrote in message
news:Td6dnW6VBogkT23eRVn-qA@comcast.com...
> Hello,
>
> I am in the process of getting bids to replace my Trane 2 1/2 ton XV1500
> heat pump and the XL1200 air handler which is 14 years old. I've had 2
> carrier dealers provide a bid and 2 Trane dealers provide bids. One of the
> Trane dealers spent several hours here measuring each room and mapping out
> the entire house. He then left and called back and said the heat calc
> indicated a 4 ton unit would be required. Each of the other dealers said
> no way but none had done a heat calc. The other Trane dealer came out with
> a laptop and did the process here and came up and said a 2 1/2 ton is need
> and that a 4 ton would create all kinds of problems short cycle etc.
>

LOL...seen this all the time...

Ask EACH of them the following:

"Did you perform a manual J?"

IF anyone says yes, tell them thanks, but you are looking for a competent
contractor.

It does not matter what part of the country you are in, with a heat pump you
get a manual T...if they cant do the proper load calcs, they can pound sand.

> Here's the details:
>
> 1. Located in Pacific Northwest
> 2. 1800 sq feet
> 3. new Milguard vinyl windows installed throughout 2 years ago
> 4. Floor, walls - R11 insulation
> 5. Ceiling R30 insulation
>
>
> The major difference between the 2 are the floors and infiltration. Both
> claim to have used the same parameters!
>
>
> I'm no expert in heat pumps and I thought bringing in reputable dealers I
> would get the straight scoop!
>
> Any advice?
>
>
> Vic
>
>

Dido

2006-02-15, 8:21 pm

was a original 2.5 ton doing job ok
then you should stay with 2.5 ton
and if you want little reserve put in 3 ton
I will agree with other guys 4 ton for you
size of house I would say slightly oversized.
Good luck from Dido
********************************
"Vic Spainhower" <vic@showsec.com> wrote in message
news:Td6dnW6VBogkT23eRVn-qA@comcast.com...
> Hello,
>
> I am in the process of getting bids to replace my Trane 2 1/2 ton XV1500
> heat pump and the XL1200 air handler which is 14 years old. I've had 2
> carrier dealers provide a bid and 2 Trane dealers provide bids. One of the
> Trane dealers spent several hours here measuring each room and mapping out
> the entire house. He then left and called back and said the heat calc
> indicated a 4 ton unit would be required. Each of the other dealers said
> no way but none had done a heat calc. The other Trane dealer came out with
> a laptop and did the process here and came up and said a 2 1/2 ton is need
> and that a 4 ton would create all kinds of problems short cycle etc.
>
> Here's the details:
>
> 1. Located in Pacific Northwest
> 2. 1800 sq feet
> 3. new Milguard vinyl windows installed throughout 2 years ago
> 4. Floor, walls - R11 insulation
> 5. Ceiling R30 insulation
>
>
> The major difference between the 2 are the floors and infiltration. Both
> claim to have used the same parameters!
>
>
> I'm no expert in heat pumps and I thought bringing in reputable dealers I
> would get the straight scoop!
>
> Any advice?
>
>
> Vic
>
>

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