Best Of

I went back to this furnace today. First thing I did was measure TESP with just the fan running. I measured 0.53". It was better than I expected. Pressure drop through the evaporator coil was low.

Then I went to measure temperature rise. The burner is equipped with a Carlin 70200 primary control and I noticed the burner was running for 5 minutes before the fan and limit control brought the blower on! So I drilled a hole in the jacket to measure temperature next to the fan and limit helix . The "fan on" setting on the fan and limit control was factory set for 110⁰. The blower didn't come on until the limit control was at 150⁰ and my thermometer was measuring 170⁰. After 13 minutes of operation my temperature rise was 63⁰.,

At this point I was satisfied that a defective fan and limit control was the reason for the heat exchanger failure. I repeated my test and recorded a video of the malfunction. I called the Williamson-Thermoflo tech support agent and informed him of my findings.

He continued to insist that the chimney was the problem and on top of that he said he never, ever saw a heat exchanger fail where the cracks are in my picture. He said he would need to see my a piece of paper go through the cracks or pictures of open holes before he could confirm that the heat exchanger has failed. He said the fan and limit control malfunction could not cause that. I insisted that my combustion analysis and pictures prove the heat exchanger failed.

Fortunately the good folks at the warranty department at Williamson-Thermoflo have provided my company a written confirmation that the warranty claim has been approved at this point.

Despite the way they insisted that a "cold chimney" was the culprit the installation instructions did not state that the furnace can't be installed on an exterior masonry chimney.

Solar is a potential option, however, the design of the structure was not set up for passive. Active solar has its own power challenges and more importantly, this building is being built in an area that sees minus 20 or more on many winter days. Solar will only be helpful during the shoulder seasons and there are complications in doing solar thermal without power.

The initial design we proposed involved Danfoss non- electric thermostats and zone valves, radiant floor heating in concrete, heated by a gasification wood boiler to use the abundant beetle kill pine, and two PV powered circulators backed up by battery that were mounted outside with the boiler. Super simple and effective.

I built this clear pump display to try and observe the small spring checks in action. The IFC fit right into the discharge of the circulators. They have a low "pop" pressure, around 1/2" psi.

First off you want to have some sort of strainer, filter, dirt separator in the piping. It doesn't take much more than a grain of sand to hold them open. See the particles on the paper towel.

On my first run I had some of the clear plastic machinings in the piping and it held the check completely open immediately.

Next the pump and circuit needs to be 100% air free. On first start the air entrained in the fluid would cause the check to bounce, flutter, chatter, pick a word. In this short demo loop it took less than a minute for the air separator to clean the fluid of all air. The check operated smoothly from then on.

Troubleshooters tell me they have replaced these damaged checks after 3-5 years of service. I suspect the checks chatter themselves to an early death.

The check is in a turbulent condition this close to the impeller. Most any check manufacturer asks for several pipe diameters distance between a pump discharge and the check.

All in all, properly protected and commissioned I do see the value in these spring type, conical seal type of checks in circulators.