(02-02-2018, 10:54 PM)blackhat Wrote: Gas line sizing isn't done by any form of pressure test. Its a series of calculations applied to the job and then used with a set of tables. If you can supply a sketch with distance measurements from meter to appliances and the appliance gas consumption numbers, I'll do a sizing for you. As you've noticed there's a myriad of venting systems used and each appliance has its limitations on the lengths to the venting permitted. That info can normally be found in an online copy of the install manual for a unit you're interested in.
So here is what I found:
Meter says "175 CFH @ 1/2 Diff." and "5 PSI W.P."
Line coming out of meter into house is 1.35" OD (assuming that is 1"...)
I didn't go into the crawl space, but can if need be to confirm sizing or where it decreases size down there. Measuring across the floor, there is right at 50' of pipe by the time it goes down into the crawl space; over; across; then back up through the utility room floor.
That should require four 90
o turns (I can't imagine they'd have used any more). There would be another three 90s to get to where I'd hang the heater.
It is 3/4" pipe where it comes out of the floor. There is a 3/4 x 1/2 x 1/2 Tee that takes gas from that pipe to the furnace and current heater. Would be no problem if I need to change that to a 3/4 x 3/4 x 1/2 Tee.
The furnace (Rheem model RGLG-10EBRJR - installed 1993) says it is 100,000 BTU/hr. (Of note...1993. I'm assuming that furnace will not outlast our next water heater. It heats the house well, so we'd go with whatever is an "equal" replacement today. With higher efficiency is that the same or lower BTU???)
No other gas appliances.
Appreciate any advice you can offer!!!