need your advice on placing the exchanger!!

[dahmower]

Please give me your opinion on where to put the heat exchanger, should it be placed in the cold air return or on the other side where it is pushing the air through the exchanger??
And is bigger always better on exchanger size?? My thinking is the larger the exchanger is the more surface you have to remove heat from.

Just my 2 cents!!

 

[Penguins87]

I was directed to put the water/ hot air exchanger in the plenium above the oil burner. That way the air is pushed by the fan through it. Mine works great!
Secondly, you should get the exchanger that best fits in your plenium. My plenium is 20"x 20". I purchased a 19"x20" exchanger and rivoted a 1" piece of aluminum angle iron to the back and both sides of plenium. Creating alittle shelf for it to sit on. Then just slid the exchanger in. Also filled the 1/2" gap on both sides (very important all air must go through the exchanger).
I was told by HVAC pro that if your house is ducted for say 150,000 BTU system thats all you will get through the duct work. No sense putting in a 250,000 BTU furnace. "Its like having a garden hose hooked to the base of the Hoover Dam". All that water, but you will still only get a hose full.
Good luck!

 

[Medman23]

There is more at work here than just size. Factors to consider for heat transfer to the air in the plenum are cold air return temp, humidity, air speed, water flow in GPM, inlet water temp, and differential pressure drop across the exchanger for both air and water.
Exchangers are rated for btu delivery to the air at a standard air speed with a standard delta T temp drop in the water - usually "X" btu at 1200 cfm with 20* drop in water temp.

There are calculators for this; you input your numbers and get an idea what type of flow you need, how many passes in the exchanger, etc.

Also, not all exchangers are equal - you get what you pay for here, so it is worth the time to do the math and get the best exchanger you can afford.

The exchanger should be in the plenum after the burner and fan, and above the A/C coil if installed. Make sure it is accessible for cleaning, as the fins will collect very small dust particles even with the good filters (I use 3M Filtrete).

There is a wealth of information on this subject here:

http://www.**********/econtent/index.php/forums/viewforum/21/

I hope this helps!