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Author Topic: Heat exchangers  (Read 2563 times)

willieG

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Re: Heat exchangers
« Reply #15 on: February 12, 2013, 06:58:07 PM »

i amsure many dont and in older homes they are likley way over sized but if y ou  arein a fairly new house (at least hear in ontario) i think a heat loss is required by some  county laws...and i know when i put my inground water furnace in the company not only did a heat loss but did an infa red phot to see where the most heat loss was so i could use this info for future insulating as i tried to improve things

the first two years i used only the water furnace the heat coil (that i never installed becasue i had a fire place) has a light on it that tell you when the furnace can not keep up and it is using electricity to heat the house only came on 2 times..so their calculations i think were quite good

i think most calcualtions are better now than years ago...years ago the plumbing guy sol the furnace and he sold what ever he was getting a deal on

it is my belief you should still "fill your plenum"
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Scott7m

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Re: Heat exchangers
« Reply #16 on: February 12, 2013, 07:12:40 PM »

Yep Ontario has far more regs according to the guy at empyre

From what he says they do mostly low fan speed settings that
Never shut off.

He was the biggest hvac guy in Canada for a long time

I put in as big of a coil as the plenum/duct work will allow

If they have a 14x14 trunk line and a heat pump will heat there home with 88 degree air,
I know my 14x14 coil will easily do it with hotter air


There is a huge difference to installing your own vs seeing a different situation every other day
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willieG

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Re: Heat exchangers
« Reply #17 on: February 12, 2013, 07:17:33 PM »

I'm just not convinced a little bit of restriction amounts to much...
[/quote]
i agree with you 100% but if you restirct a plenum that is 20 inches high by 2 inches that would be 10% i think that is more than a little (but we all have different views of "little bit"
would a 10 percent blockage put more back pressure on your blower? would it cause any early failure of the blower? i don't know these things so that is why i chose to fill my plenum as best i could..i would think the exchangers them selves are causing some added restriction on the blower motor all ready

and i am not arguing with you either..just putting another view out there for interested parties to  sipher on (lol) i have no proof of any of this..just my twisted thinking. i always like your (and other) responses..give me (and others i hope) more things to consider when we are trying to decide
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Scott7m

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Re: Heat exchangers
« Reply #18 on: February 12, 2013, 07:25:55 PM »

I'm not arguing either....

I jut know it's impossible in the real world to get things so precise.....  I used to freak over things like this.  I always do a pre run on the install doing the estimate where I see where I can install as big of a coil as possible...  Usually here it's a 14x18 or 16x18

I've also played with my own to see if allowing air gaps around the sides of the coil amounted to much, I allowed 1" gaps all the way around the sides of my coil and air temp out the vents only dropped 4-5 degrees. 
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Scott7m

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Re: Heat exchangers
« Reply #19 on: February 12, 2013, 07:57:18 PM »

Hey Willie, help me figure this out

If your flowing 6 gpm, and you have a delta t of 20.   How many btu can you actually push through? 

360 gallons an hour, delta t of 20 degrees.........  I'm thinking
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Scott7m

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Re: Heat exchangers
« Reply #20 on: February 12, 2013, 08:36:51 PM »

The results are very interesting, makes you think that the btu ratings we see on heat exchangers is worthless information...

They have no idea how many gallon your system will push, what your delta t would be and so on

For example the figures Willie confirmed me on was if you were pushing 6 gallon per minute and had a delta t of 20, the most btu's you could deliver is 57,000 per hour

You could speed the water up to let's say 10gpm but it wouldn't still get you anywhere near the ratings we see, and you really don't want the delta t more than 20 so...  You can easily see if your needing a lot of btu, big line is essential
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willieG

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Re: Heat exchangers
« Reply #21 on: February 12, 2013, 09:33:11 PM »

the reason we see such high btu numbers on exchangers is the one we buy are normally for uch different applications. if you look on the tags tehy may say something like "Max pressure 300 psi" and "Maximum temp 300 degrres F) these exchangers are also used for steam pressure where temps can be much hotter  than we create and are capable of delivering the  btu they are rated at

with our little OWB we will never be close

the gpm  and the temp you deliver at AND your delta will tell you how many btu you are delivering to your house
 any change of those three things(or any change of any one of those three things)  will change the btu you are putting into the home




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Scott7m

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Re: Heat exchangers
« Reply #22 on: February 12, 2013, 09:36:51 PM »

Yep.... 

So picking out heat exchangers based on there rated btu's is hokum
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automan77

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Re: Heat exchangers
« Reply #23 on: February 13, 2013, 09:11:50 AM »

Talked with a dealer/installer and he told me to go with the same btu as my propane furnace which is 70,000 btu
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comnrailpwr

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Re: Heat exchangers
« Reply #24 on: February 13, 2013, 11:59:59 AM »

i didn't meet my flanges in the middle scott, i set one up against teh other so i only have the thickness of 1 flange. so i have three flanges..one on each side and one in the middle that was the way i could do it to get the least "restriction" due to the flanges


I see


I'm just not convinced a little bit of restriction amounts to much...
In heating, restrictions do not mean a whole lot, during heating the fan is run on medium speed unless heat source is a heat pump. Air conditioning and using heat pumps is where too much restrictions can cause problems. Coil flanges will make no difference in the operation of the original equipment, they wont cause enough restriction. HVAC systems should be designed off the cooling load. Its easier to heat a home than it is to cool it.
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Scott7m

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Re: Heat exchangers
« Reply #25 on: February 13, 2013, 04:46:28 PM »

Talked with a dealer/installer and he told me to go with the same btu as my propane furnace which is 70,000 btu

Sounds far more reasonable....  The 12x18 will easily take care of you, with a proper pump and 1" lines you should be able to push that

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automan77

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Re: Heat exchangers
« Reply #26 on: February 13, 2013, 06:28:53 PM »

anyone ever buy a heat exchanger off ebay, there seems to be some good prices on there but not sure of the quality.
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Scott K
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Scott7m

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Re: Heat exchangers
« Reply #27 on: February 13, 2013, 06:34:14 PM »

anyone ever buy a heat exchanger off ebay, there seems to be some good prices on there but not sure of the quality.

I have before in a pinch, I just don't trust everything I see on there

The 12x18's I carry I sell for $151 w/free shipping...  I trust them and have sold hard telling how many wih no problems

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ghitch75

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Re: Heat exchangers
« Reply #28 on: February 13, 2013, 06:55:12 PM »

Quote
In heating, restrictions do not mean a whole lot, during heating the fan is run on medium speed unless heat source is a heat pump. Air conditioning and using heat pumps is where too much restrictions can cause problems. Coil flanges will make no difference in the operation of the original equipment, they wont cause enough restriction. HVAC systems should be designed off the cooling load. Its easier to heat a home than it is to cool it.

thats all good with gas and oil but electric air handlers with heat strips if you stick a water/air coil in the supply air it will burn the heat strips up from to much restriction and turbulence........i always put the coil in the return.....
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Scott7m

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Re: Heat exchangers
« Reply #29 on: February 13, 2013, 06:59:43 PM »

I never install in the plenum


I always try to install in the main trunk line supply

If that don't work I'll go to the return side and make a new filter space.

If you install in the supply side of the main line the air is already filtered
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