Hot Water Boiler to Forced Air Ducting

danzig · Post by **danzig** » Thu. Dec. 11, 2008 9:39 am

Hi guys I am asking for some insight on buying a boiler and an installing water to air heat exchanger. My father has a gas forced air furnace. He is wanting to install a supplemental (secondary source of heat). He is having a hard time deciding on a forced air coal furnace or a coal boiler. The house he has is a brick 3 story house (appx. 100 yrs). He is in the process of adding on to the house.
My question is how well do the water to air Heat exchanger (HX) work. can you give me some insight. Does the heat exchanger interfere with the blower and air distribution of the gas furnace ducts. Will the house have reduced air flow or Cold spots? Or is my dad better off getting a forced air coal furnace?

Poconoeagle · Post by **Poconoeagle** » Thu. Dec. 11, 2008 10:49 am

FYI just saw this...

Personally I prefer hot H2o to air but you already have a duct system...
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VigIIPeaBurner · Post by **VigIIPeaBurner** » Thu. Dec. 11, 2008 11:34 am

Poconoeagle wrote:FYI just saw this...

Personally I prefer hot H2o to air but you already have a duct system...
**Broken Link(s) Removed**

About the add... called Keystoker last month to check on DV pricing. If there's no dealer in your area, they'll sell to you direct. New price for a DV Koker is $300 LESS than what the craiglist lister wants

That price dropped $200 since the first listing, if I recall right.

Search on member Coalkirk's listing. He has posted a pic of an install like your inquiring about here: Opinions on Stove Choice

Poconoeagle · Post by **Poconoeagle** » Thu. Dec. 11, 2008 11:49 am

Wow.. it definitly pays to do homework.

VigIIPeaBurner · Post by **VigIIPeaBurner** » Thu. Dec. 11, 2008 12:19 pm

Poconoeagle wrote:Wow.. it definitly pays to do homework.

Sure is a

... but if you need it now and can pay the premium ....

Other threads conclude that Keystoker's output is being hindered by suply-line issues beyond their control. See Keystoker Production

LsFarm · Post by **LsFarm** » Thu. Dec. 11, 2008 10:59 pm

PM forum member Yanche and coalkirk, both use a hot water to hot air exchanger for their houses.

I'd recommend the boiler and a water to air heat exchanger in the heat ducts.. using hot water baseboards or the best way is hydronic hot water heated floors for the additions to the house. A boiler will also provide all your domestic hot water during the heating season.

There is some air flow restriction in the ducts, but most people set up the distribution fan to run full time at a lower speed, and control the heat with the water flow to the heat exchanger. This reduces or eliminates the 'hot blast' of scorched air followed by a cool down typical of forced air systems.

Greg L

coalkirk · Post by **coalkirk** » Fri. Dec. 12, 2008 6:57 am

I'm not an engineer so I designed my system by the seat of my pants. What occurred to me is that the coil needed to have a larger surface area than the duct or the air flow would be adversly affected. Last year, my wifes cousin bought a coil that was the same size as the duct and it just didn't work as the air flow was severely restricted. Notice the transition in the duct to the heat exchanger in the picture below. I'm sure there is a more exact way to chose the coil size and I'm betting Yanche could tell yoou what it is. I decided to go "big" and regulate the temperature with a tempering valve. I send water through my heat exchanger that's about 95 degrees on most days. If it gets really cold, I'll bump it up.

.JPG | 127.4KB | heat exchanger.jpg

Well that pic doesn't show it as clearly as I thought but you can see how the duct tapers before and after the heat exchanger.

LsFarm · Post by **LsFarm** » Fri. Dec. 12, 2008 8:00 am

Coalkirk, do you run your distribution fan full time at a lower than normal speed? Do you have any idea what the cost is? [KW/month] ?

Greg L

coalkirk · Post by **coalkirk** » Fri. Dec. 12, 2008 9:49 am

Hi Greg,

Yes, I do run the fan full time at a lower speed but I do not know what the cost is. The air handler is a 15 amp 240 volt so I'm pulling half the amperage of a 120 fan.