Thread: New one for me

I have never seen this before. Someone removed one of the burners in a 50K gas furnace. The remaining burner was half covered in rust.

How did they seal the gas manifold?

No reason to remove a burner unless it rusted out and they couldn't find one, looks like they sealed the manifold with an orffice plug. The pilot burner and thermocouple are still in tact and will lite the one atmospheric burner OK. The problem is condensation will build up on the left side and eventually rust through the heat exchanger. Depending on the age, the fan/limit switch needs to be on the right side to start the fan unless it is timed start from a circuit board, but then the limit switch also needs to be on the right side to protect for hi temp. Anytime someone removes a burner there are so many other factor that are involved in the operation and safety of the furnace. The burners can still be replaced and the heat exchanger cleaned unless it is too late. This needs to be put back to the original design cleaned and tested for CO, or the furnace needs to be replaced.

This unit is about 20 years old. They put a brass plug in the manifold. The one operating burner was half covered with rust. It was a mess.
The house was a flip, and I told my client that the HVAC system really needed to be replaced.

Replacing a gas orifice with a plug was a common, but ill-advised method of derating a furnace back in the days of gravity vent furnaces. The recommended method was to reduce the orifice size on all the burners.

In both cases, gas valves, burner baffles and flue baffles must be adjusted to prevent flue gas spillage, over-firing and to maintain an efficient gas flame. A combustion gas and flame analysis should be performed after each adjustment to confirm the burners are functioning efficiently.

The presence of excessive rust could indicate the flue was too large and not baffled properly. This would cause slow draft resulting in excess condensation inside the flue pipe which would run back to the heat exchangers and burners causing premature rust.

There are other possible causes for the rust. This is just a likely scenario due the presence of the plugged burner jet.

I think this one was rusted because its over 20 years old, and was not serviced for a long time. Since it was only a 50K unit to begin with, I'm thinking that taking out one burner is going to make it insufficient to heat the house come winter.

I told my client that the HVAC system should probably be replaced.