Author Topic: Water heater waste heat of an oil furnace  (Read 1707 times)

0 Members and 1 Guest are viewing this topic.

Offline Wolvenar

  • Senior Moderator
  • Hero Member
  • *******
  • Posts: 1466
  • Karma: +40/-0
  • Mr. Murphys pawn
Water heater waste heat of an oil furnace
« on: January 09, 2012, 05:15:00 am »
We never used this for the intent I built it, as it turned out it wasn't
even good enough to work as a preheater.

But it was fun to build.

After seeing a lot of discussion of batch heater, heat reclamation, and TomW's example of a simple couple tanks outside as water preheater system. I wondered if I could pull something off, if only as an experiment.

I started off searching for a couple water heaters that were being thrown out.
 I had by chance stumbled onto the perfect pair for my needs.
One was just a bit larger in circumference so it could fit inside the other, and almost a perfect height also

I cut the top and bottom of the larger out with the top just big enough to tightly slip the smaller inside

Slipped the smaller one in and left it about 3 inches off the bottom,
This left just shy of 1.5 inches (38mm) between the inner and outer tanks.
( not shown but I welded a couple side braces  on the bottom also)

Welded up the top
I don't know why but I had a really rotten time holding an arc welding this,
could been partly from my mask fogging up from my breath in the -15F

Welded on a bottom, still had that problem welding this thing.

And like many of my other projects I either neglected to take photos of it finished and in use, or I cannot find them. I didn't publish them to the gallery, so if I have some it could take me a long time to find them.
However with this project I do not think I did ever take any pictures of it in use, as I was rather disappointed with the outcome.

I cut into the outside tank and welded in a 6 inch inlet pipe on one side on top.
On the other side I welded on a 2 inch pipe in the center. As the center tank only had a 3 inch pipe through it I figured I better make up at least most of the missing airflow. I fit a 6 inch again on the center tanks top and routed a 2 inch from the side to meet it

This worked out well as I put it above and inline of my furnace. the airflow had to go down to come out of the inner tanks top, and part of it around to the 2 inch on the center of the other side.

Then into the normal piping above the furnace was a couple day project
 to build a sturdy non flammable place for it to rest
Calibrating the burn of the furnace went easily, it seemed to not dislike the new exhausting setup,
so I figured I was set.

I filled the tank with water, (53F) and turned up the heat.....
6 hours later, in those still -15f temps the water was only 87F 
This is just sitting water nothing was passing though as it was not piped into anything yet.
10 hours later. 84F..
22 hours later, 89..
2 days 81 ( outside temps in the + 10F)
I drained and refilled it
This time it took 12 hours to get to only 82f

At this point it was obvious this wasn't gonna work.
So talking to the IRC guys, they figure the furnace didn't work hard enough to heat our well insulated house,
and it was re-cooling between fires from the chimney draft.
We tossed around a few ideas, but in the end I decided it was not worth leaving in.

Oh well that's why we do this stuff, to learn right?
Trying to make power from alternative energy any which way I can.
Just to abuse what I make. (and run this site)