A couple of weeks ago, I had a call from a commercial customer, who stated that one of their package rooftop heaters "made the store smell like gas when it ran".
It's about a 15-year-old Ruud. It has a forced draft blower, as opposed to an induced draft blower. A really dumb design. You can't troubleshoot the thing correctly, because when you take the cover off to get to the gas valve, ignition module, and burners, you expose the draft inducer and lose your forced draft.
Anyway, after a bit of poking around, I concluded that the hx was bad. This unit is a rotted out sack, to say the least.
I told them what I found, and quoted a replacement. several days later, I called to see what they wanted to do.....they said that somebody had already fixed it.....oh, really?
I stopped today for a peek.....couldn't believe what I found. Somebody had plated over most of the side vent outlets, and had installed an induced draft blower over the remaining outlet louvers....then they took a piece of 12" metal duct, and fabricated a "shroud" to protect the draft inducer.
Yikes !! I'll get and post pics later this week.....
I'm guessing, that they found what I found. So, they converted it to induced draft instead of forced draft to "get by".