I noticed some confusion between the codebook and training module for piping that I was curious if anyone has an "input" on.
Now I know there's a ridiculous amount of spelling errors and minor mistakes throughout all of these modules as nobody took the time to proof-read any of them before mass producing them, but this stood out to me as I've been involved in gas fireplace installations for years, and we very frequently use 3/8" copper tubing with runs up to 30' and sometimes 40' for a low enough BTU fireplaces. Many of the POS builder fireplaces are in the 17,000 btu range, and some as low as 13,000 btu maximum input.... There are, literally, hundreds (if not thousands) installed this way in my area.
So here's the parts that don't quite make sense to me:
G3-Module 8-2010 version, pg 21 under "indoor installations", reads: "the minimum pipe size that can be used for indoor applications is 1/2" diameter; however, 3/8" diameter tubing may be used for branch lines that are 25' or less in length, and that do not supply more than 15,000 btu/h."
Closest thing in the codebook b149.1-10 that I can find to back up this rule is on pg 37. 6.3.8.2 "For propane, piping less than nps 1/2" shall not be used indoors, except that nps 3/8 piping may be used as a branch line not exceeding 25'"
I think it's just another module error where the guy got his tubing/piping rules mixed up. The codebook is very precise when they're referring to tubing and/or piping. I'm just really confused by where he came up with the 15,000 btu rule.
I also completely understand how we size piping with LMR while staying in the CZ and all that, but I've been told that when we use "copper tubing" branch lines, we don't need to count these branch lines as part of the LMR. We can simply sneak these in a system because it's a different material and just need to ensure it's adequately sized for the appliance it serves... It makes absolutely no bit of sense to me, but that's why I've been hearing several times from other teachers and g2's... I'm curious what others have to say about that.
I know this rule can mean the difference between a customer having to spend an extra grand, or more, to up-size a piping system that may not need to be upgraded at all.
If you suddenly decide to use iron, you have to upgrade the main line, but if you choose copper, or CSST, you're off the hook? It doesn't make sense.
I've never heard of a 15,000 BTU rule.
Clause 6.3.8.2 would apply to propane piping, not tubing. All 3/8 NPS natural gas threaded piping would have to be Schedule 80, as per Clause 6.3.8.1. Using 3/8" copper on a propane or natural gas system is okay as long as it's sized properly, regardless of length.
QuoteClause 6.3.2 - A piping or tubing system supplied at pressures up to and including 14 in w.c. (3.5 kPa) shall be designed to prevent the loss in pressure between the appliance and either the termination of the utility installation or the last-stage regulator from exceeding the maximum allowable pressure drop specified in Table 6.1. The minimum size of pipe, tubing, and fittings shall be determined in accordance with good engineering practice, such as
(a) by the use of Tables A.1 and A.8 of Annex A for natural gas, which include allowance for a reasonable number of fittings, when the maximum allowable pressure drop is 0.5 in w.c. (0.125 kPa);
(b) by the use of Tables A.2 and A.9 in Annex A for natural gas or Tables B.1 and B.6 in Annex B for propane, which include allowance for a reasonable number of fittings, when the maximum allowable pressure drop is 1 in w.c. (0.25 kPa); or
(c) by the method of calculation outlined in Annex A for natural gas or Annex B for propane.
The Gas Code Section E Piping Design System is clear,
QuoteE.2.2 - The pipe size for the sections from A to all appliance outlets shall be determined.
Yeah, the 3/8" they refer to in the codebook is piping and not tubing at all. I don't know of any person who would attempt to run 25' of 3/8" schedule 80 black pipe. Our suppliers don't even bother carrying lengths of it. The smallest black iron I've seen is 1/2" and then the only time I've ever used 3/8" iron is when I'm reducing with nipples to go into a valve, or BBQ quick disconnect...
With the branch lines of copper, I usually chart out how many left over BTU's the customer has on their existing system with the LMR and use proper judgement from that point on where I Tee into the system for what I'm adding. If I think it'll throw it off, I either run it back to tie in within 24" of the gas meter, or get them to upgrade the main coming in.
I know the codebook is going to ensure more then enough btu's for all general appliances, but when you have every appliance with a 3.5" w.c. at the main valve, and incoming pressure of over 7" w.c., wouldn't that appliance still function fine if it had a pressure drop over 1"?
I took out a furnace recently that actually had an allowable pressure drop stamped on its tag stating it could handle a 2.5" pressure drop on a system with an incoming pressure of 7" w.c.
I do see several undersized system and wonder how they still function fine, and that's probably cause they can handle more than a 1" drop in the 7-14 chart.
See Table 6.1 below. If the supply pressure is below 7" w.c. the maximum allowable pressure drop is 0.5" w.c. If the supply pressure is between 7 - 14" w.c. the maximum allowable pressure drop is 1" w.c.
Even if the furnace works and is approved for a higher pressure drop I wouldn't exceed the values found in Table 6.1.
In the Ottawa area, and just working in residential, for the most part we've always used the 7-14" tables. Every pressure we've ever tested was set at about 7" or a hair more. Do you ever see any that are below 7"? To then have to drop to the lower chart of .5" allowable drop?
15 years ago I used to work on gas meters without regulators that were supplied a low gas pressure but I think it was still over 7" w.c. I don't remember ever seeing less than a 7" w.c. supply pressure.