Natural gas smell from turning on a second furnace

Whutt316

Hello,
This problem is confusing me. I have a garage that is detached from my house. When I turn the furnace on in the garage, my house smells like natural gas. This smell only is noticeable when I turn on the furnace in the garage. I have 4 things in the house that are ran off of natural gas. My furnace(in the house). my clothes dryer, my stove and my hot water heater. I have talked with some people about this and they think I am crazy. Any help would be appreciated.

Thank you

Zman

Tell us a little about the gas line size and routing.
Do you have a manometer?

JUGHNE

Any problem with the pilot lights on the stove going out when you start the 2nd furnace?

HVACNUT

Yeah can you post BTU ratings of all gas appliances, meter and pipe sizes?
Seems like a major drop in gas pressure and incomplete combustion.

mattmia2

call the utility and have them investigate to make sure it is not leaking.

PRR

I had that with a large water-heater on a small propane tank that we let get low. The pressure got lower than the burner was designed for. The poor combustion spilled unburned gas into the house. Getting that tank topped-off was the instant fix.

My guess (and I think everybody's) is that your pipes were sized for less load than you have now. This happens when loads are added without checking pipe sizes. Draw out the system, pipe lengths, sizes, elbows, supply and loads. Then do some hard arithmetic with the AGA tables. (A Master Plumber can do this faster than you, and a neat sketch may save him some time.)

mattmia2

You can also do it with the equation, which might be best for your case, any table method is going to overestimate to one extent or another and doing it with the equation will tell you exactly what parts you must make larger.