Power Failure Question-

adirondacklady wrote:Ok, I understand that the fire goes out within 10 minutes if the power goes out. Here's another question: If there is no power to the powervent, how are the gases and exhaust drawn out of the house during that 10 minutes that the fire is still burning? Does it not come back into the house?

Diana

OK, so I had to get my LeisureLine Pioneer with Power Vent through a pretty rigourous and difficult inspection/approval process in my town. In the end my design was approved. Plug the power vent into a battery backup (an APC UPS from Staples, $109) and plug the WMO-1 safety switch (which feeds the stoker/blower/combustion fan) into the regular utility or non-battery outlet on the UPS. I am attaching the final approved wiring diagram.

In my setup running .06 draft the fan will run between 60-83 minutes. It's far longer than the fire will burn.

I must have missed something ? From the diagram I see above if the power vent clogs or fails (not because of power outage) The stove still has power and will continue to burn. I thought the whole purpose of the wmo-1 switch was to shut the stove down if the power vent failed and I can't see how this would happen here ?? I have my power vent and stove powered off the wmo-1 switch if the stove shuts shuts down I was told you also wanted the power vent to shut down so it wasn't sucking air and making it possible for a hopper fire.
I guess I need to know what the wmo-1 is actually sensing heat ? co ?? or what it is supposed to do thanks
Chris H

First - A serious word of caution about your setup! In my diagram I note very strongly not to power the stove through a battery backup. If you do the fire and fan will continue (in your absence) until the battery is exhausted. Once that happens, you now have a healthy fire with no draft and you're right back to adirondacklady's initial comment. Leisureline in their installation instruction is very clear about plugging the coal-trol into the WMO, and the powervent into the WALL.

In normal operation the draft sucks air in through the WMO switch. When the draft is impeded or absent but there is still coal-trol power, the heat (200F or more) backs up into the WMO and opens the circuit gate, which kills power to the coal-trol (which is supplying power to combustion, convection and stoker). This also would happen with a natural draft chimney.

If the power fails, the Powervent continues to run, but the draft drops considerably because there is no longer the combustion fan pushing air into the stove. With a natural draft chimney you would still have draft as well - you can't stop the natural draft of a hot chimney. The fire may continue to burn, but it will not be fed any more fuel, and you Definitely are not forcing air up from the bottom of the grate at a rate that supports combustion. Assuming you're not overdrafting (and have a barometric damper installed) I don't expect the fire would continue to burn and spread to unlit coal. I will most Definitely test this and report back, but perhaps Jerry (LeisureLine) could comment.

Well, I did confirm my thinking with a test. I took a raging 6" deep fire and killed power to the stove. The powervent continued to run. After 73 minutes the battery ran out and I had no coals left on the surface that were lit, and some red coals on the bottom about the size of 3 finger tips. The fire did not back up into the bin while drafting steady at .05, even though there was plenty of fuel for it. My assumption that draft would drop considerably was incorrect. It only fell off slightly at .01".

The fire took longer to burn out than I expected, but I'm satisified with the results. If the power had failed in the middle of the day or night when I run smaller fires, I'm certain it would have been completely extinguished within 30 minutes.

Thanks for the question, and I'm more comfortable now that I know the answer myself.

Bill