Natural gas question

[10towers]

Hey guys I have another question maybe you can help me.

How many percent of natural gas is needed to start a normal combustion (ignite) a residential furnace for heating?

[MikeHolm]

Weird question dude. The limits of combustion is 4-14% but that won't matter about starting up a furnace. You usually need to have around 7" of gas pressure at the input to the gas valve (regulator) to drive it properly and which reduces it normally to 3-4" running pressure. Hope that answers it.