1970s Heatilator?

[ThirteenEcho]

I’m brand new here. Bought a house 10 yrs ago that was built in 1978. The natural stone fireplace surrounds a steel firebox. Two air inlets low on the hearth and either side of the fireplace opening house squirrel cage fans that kick on when the fire achieves a certain temperature (assuming there is a thermocouple in the surrounding airbox that activates fans). One air outlet immediately above fireplace opening and two outlets coming off the top of the surrounding airbox ducted to other parts of the house. Everything still operates as I assume it did when constructed/installed 47 years ago.

I’m assuming it’s a Heatilator, but can’t find a data plate. Popular Heatilator models for that time are Mark 123s, but who knows? One Mark 123 38C installation manual looks very close to what I think I have.

My question:

The fireplace has a glass door (assuming pyro glass as it’s never shattered) and a screen/mesh door that I close during operation. It’s far from airtight but I was told I don’t want an airtight door as it will cause the firebox to heat up too much and could damage the steel firebox. Still I get roaring fires especially at start up. But can Heatilators operate with closed doors, or are they supposed to be operated with doors open (all assuming this is a Heatilator)? I can’t find that information anywhere.

BTW, open doors of course allow a lot of combustion air into the firebox, so my wood consumption would be significant. I’m consuming plenty of wood already the way I’m burning with leaky doors. Just want to make sure I’m operating it correctly, even though I’ve done it this way for the past 10 years.

Thanks.

 

[begreen]

There's a good chance that the doors are tempered glass and not ceramic glass. Keeping the doors open when actively burning may be to protect the glass.