Valor 739 ILN

[Moritz]

Installed 2 Valor 739 ILN inserts back to back in a see through masonry fireplace. Both sets of 3" venting share the same 16x16 flue. Made a custom box out of sheet metal that fit into the flue to expand out to accommodate both terminations. Terminations are fairly close together and now have sheet metal separating the two.
Client now has troubles turning on one of the inserts if the other one has been running (some of the time). Never has a problem lighting the units if both are turned on at the same. Would the heat from the exhaust on fireplace 1 have an effect on my downdraft/fresh air on f/p 2? Anything I could be missing or any trouble shooting?
The client lives in the wide open prairies 3 hours away.

 

[DAKSY]

What is the gas pressure feeding the units?
I'd take a reading at BOTH valves with both off off & then with ONE burning.
The pressure may not be enough once one drawing from the gas line...
An increase in piping may be in order...

 

[robatnorfolk]

Did you install the terminals at different heights or are they right next to each other? Typically we extend one of the terminals 12 to 16 inches higher to eliminate any of those issues.