OK, this isn't pure HVAC but I know my buddies here can put me on the right track.
I'd like a tankless water heater and I've already determined that my existing natural gas line won't support it... and up-sizing the line isn't practical... it'd take a huge drywall tearout. Relocating the water heater is even less practical, so putting an outdoor-rated tankless unit closer to the gas meter isn't really any help. This is two-story condo, built on a slab, so options are few and far between when it comes to major repiping and relocation.
I have just two gas appliances; a 66k input furnace and a 40k input storage water heater. The place was clearly built with the expectation that those would be the only gas appliances ever (no line to the kitchen, no line to the dryer, etc.). The furnace and current water heater are connected at the end of a 3/4" black iron pipe, about 55' from the meter (lots of elbows along the way, too. The tankless unit I'd like has a 170k input- the Bosch with a dedicated combustion air intake pipe. Every sizing table I've ever seen indicates that pulling 226kBTU through that gas pipe is just not going to happen at standard pressure.
I know it's possible to switch to 2 psi natural gas service, using a little pressure regulator on each gas-burning appliance- I've seen it in commercial and seem to remember having heard of it in residential once in a blue moon. I know the higher pressure lets you move a lot of gas through a relatively small pipe over longer runs.
How practical 2psi residential service in the real world? Should I even bother calling some contractors to come out and have a look?
[Edited by wyounger on 04-24-2006 at 09:06 AM]
I'd like a tankless water heater and I've already determined that my existing natural gas line won't support it... and up-sizing the line isn't practical... it'd take a huge drywall tearout. Relocating the water heater is even less practical, so putting an outdoor-rated tankless unit closer to the gas meter isn't really any help. This is two-story condo, built on a slab, so options are few and far between when it comes to major repiping and relocation.
I have just two gas appliances; a 66k input furnace and a 40k input storage water heater. The place was clearly built with the expectation that those would be the only gas appliances ever (no line to the kitchen, no line to the dryer, etc.). The furnace and current water heater are connected at the end of a 3/4" black iron pipe, about 55' from the meter (lots of elbows along the way, too. The tankless unit I'd like has a 170k input- the Bosch with a dedicated combustion air intake pipe. Every sizing table I've ever seen indicates that pulling 226kBTU through that gas pipe is just not going to happen at standard pressure.
I know it's possible to switch to 2 psi natural gas service, using a little pressure regulator on each gas-burning appliance- I've seen it in commercial and seem to remember having heard of it in residential once in a blue moon. I know the higher pressure lets you move a lot of gas through a relatively small pipe over longer runs.
How practical 2psi residential service in the real world? Should I even bother calling some contractors to come out and have a look?
[Edited by wyounger on 04-24-2006 at 09:06 AM]
