Heat exchanger advice

[Pop M]

OK, I live in a double-wide that sits on a full foundation. Bought the place used and heated my first winter with propane (no natural gas available). I put in US Stove 1557 and used that for heat the next 9 years. It does alright but I'm tired of having the dust, smoke and mess in the house. I had the chance to buy a used Heatmor 200 CB and think I'm gonna take it.

My question is, where is the best place to put my heat exchanger? Conventional wisdom says to put it on the discharge of the propane furnace and use my existing blower but that would place it underneath the furnace (furnace sits upstairs and blows the hot air to duct work under the floor). No issue when the blower is running but when it shuts off the the 180 Deg heat exchanger just sits there sending heat back up into the furnace. Not a big deal with the 1557 but I think it will be a lot hotter with the outdoor burner.

My other option would be to add a second blower and duct work for it. It would still send heat to the existing propane furnace but less than having it right underneath.

What do you think? One of these options or something else?

 

[hondaracer2oo4]

Try http://outdoorwoodfurnaceinfo.com/forum/

More OWB over there.

 

[maple1]

Are you OK with using a lot more wood than you do now?

Not exactly sure about your question. I am thinking it would be OK on the LP discharge - but if it does get too hot you could likely control things so the hot water only circs through the HX when there is a call for heat.

 

[Tennman]

We use two thermostats. One for propane/AC and a dedicated boiler tstat that controls the propane furnace fan and turns the boiler circulation pump for the HX on and off. We wasted a lot of energy for quite a few years by letting the pump run continuously. When we added storage, I corrected this because I knew it would destroy the stored btus. If I understand your question, turning the pump off when the fan is off will minimize the waste heat going back into the furnace. If the furnace/blower is in the attic and one duct/plenum from the blower above to the distribution ductwork under the house, I'd be inclined to place the HX under the floor before the ductwork branches out. The room above where the boiler lines enter our root cellar and where the HX is located is noticeably warmer than other rooms. Just insulated lines and HX in the duct work leak energy, but it's in the house. If you're able to place the HX and plumbing under the floor you'll gain free benefit from this leaking energy. I'd think only practical if all of your duct work is in the crawl space. Understand 100% about getting dirt and dust out of the house along with a huge reduction in fire risk. Hope I understood your question. I'll check back in. But you definitely want to put a relay on that pump so it's linked to the tstat's call for fan regardless of where you put the HX.

Hope that helps. You're roughly installing what we successfully used for about 6 winters before we added storage.

 

[Tennman]

Correction: Just looked at my signature - 5 winters without storage. Ask away, but its a quiet time of year with most of us off messing with other matters.

 

[StihlKicking]

Not sure that I have my head completely around your entire question. As far a temperature goes, the aquastat on my OWB is set on 180 degrees. You don't want it set much higher than that or it will boil your water out. At that I have about a 2 degree loss to my heat exchanger. So the way I understand what you've stated a 178 degree heat exchanger would fit your system with an acceptable amount of heat loss? Your heat exchanger in a OWB system shouldn't ever be over 180 degrees.


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[Tennman]

Well Pop, You get anything useful or did we all waste our time?