Results 1 to 11 of 11
Thread: Direct vented gas water heater
-
11-07-2017, 03:04 PM #1
Direct vented gas water heater
Is it required to have copper tail pipes installed next to the direct flue to the exterior? One today had the copper on the cold water side but not the hot exposing the Pex. Also, it is required to have an expansion tank installed with these water heaters. This one did not.
Thanks in advance!
Jim
Similar Threads:
-
11-08-2017, 10:19 AM #2
Re: Direct vented gas water heater
The direct vent flue does not get excessively hot, so I don't see that it would be a problem. However, your local regs may say something to the contrary.
I have seen PEX directly connected to so many water heaters now that I am convinced it is not easily damaged by moderate heat. The exception would be a standard combustion type gas heater with a hot vent hood. Those need an 18" metal stub before the PEX.
John Kogel, RHI, BC HI Lic #47455
www.allsafehome.ca
-
11-08-2017, 12:36 PM #3
Re: Direct vented gas water heater
The requirement is 6" clearance to combustible material, and PEX is combustible, so a 6" minimum clearance to the vent (and draft hood) is required.
If the pipes went vertical, and if the vent went vertical too, then 18" of metal pipe between the water heater and the PEX would still leave the PEX within 6" of the vent.
-
11-08-2017, 01:13 PM #4
-
11-08-2017, 01:46 PM #5
Re: Direct vented gas water heater
-
11-10-2017, 10:12 AM #6
Re: Direct vented gas water heater
Thermal expansion protection has been in the code for many years, but around here, the AHJs have been slow to adopt it. So, I recommend checking with your AHJ to see if they have adopted the requirement.
But, several (maybe most) water heater manufacturers require thermal expansion protection, so you should be on solid ground to recommend it.
If you choose not to decide, you still have made a choice.
-
12-30-2017, 04:54 PM #7
Re: Direct vented gas water heater
A thermal expansion tank is required on the cold water supply to the tank if there is a backflow prevention device at the water meter or if the water meter has a built in check valve. This is referred to as a closed system. Another situation would be if there is a re-circulation line on the hot water as this would require a check valve thus making a closed system. On a open system as in most residential homes, any expansion of water caused by the water heater would just go back to the city water main.
- - - Updated - - -
Last edited by Gerry Pomanti; 12-31-2017 at 10:16 AM.
-
12-30-2017, 06:07 PM #8
Re: Direct vented gas water heater
That is still an open system as there is no check valve or other restriction (such as pressure regulator, etc) as the system is still open on the supply side.
On a open system as in most residential homes, any expansion of water caused by the water heater would just go back to the city water main.
Some municipalities/water utility systems do not want that thermal expansion 'push back' of water into the main, as such, some municipalities/water utility systems require a thermal expansion control device anyway ... and that could be a thermal expansion tank or a thermal expansion pressure relief valve which is then drained to a suitable location.
-
12-31-2017, 10:25 AM #9
Re: Direct vented gas water heater
Some municipalities/water utility systems do not want that thermal expansion 'push back' of water into the main, as such, some municipalities/water utility systems require a thermal expansion control device anyway ... and that could be a thermal expansion tank or a thermal expansion pressure relief valve which is then drained to a suitable location.[/QUOTE]
That doesn't make any sense. If it's an open system the pressure is always that of the city water supply.
With a hot re-circulation line you need a check valve on the cold water supply to the tank. This creates the closed loop and need for the exp tank. Every hot water tank has a temp and pressure relief valve for safety but the purpose is not to relieve excess pressure from thermal expansion.
-
12-31-2017, 12:39 PM #10
Re: Direct vented gas water heater
Originally Posted by Jerry Peck
With a hot re-circulation line you need a check valve on the cold water supply to the tank.
The recirculation pump simply ties into the farthest hot water branch end (or as close to that as possible) and circulates that water back to the water heater, usually into the bottom tank drain, where that water is reheated and circulated back out the hot outlet from the water heater.
This creates the closed loop and need for the exp tank.
Every hot water tank has a temp and pressure relief valve for safety but the purpose is not to relieve excess pressure from thermal expansion.
some municipalities/water utility systems require a thermal expansion control device anyway ... and that could be a thermal expansion tank or a thermal expansion pressure relief valve which is then drained to a suitable location
-
12-31-2017, 05:06 PM #11
Re: Direct vented gas water heater
That doesn't make any sense. If it's an open system the pressure is always that of the city water supply.
With a hot re-circulation line you need a check valve on the cold water supply to the tank. This creates the closed loop and need for the exp tank. Every hot water tank has a temp and pressure relief valve for safety but the purpose is not to relieve excess pressure from thermal expansion.[/QUOTE]
The expansion tank is there to prevent back flow into the municipal water supply. As always every jurisdiction is different but here is what the Illinois plumbing code says
ftp://www.ilga.gov/JCAR/AdminCode/077/077008900I11300R.html
Section 890.1130 Protection of Potable Water
g) Installation of Devices or Assemblies
7) Closed water systems with hot water storage shall have a properly sized thermal expansion tank located in the cold water supply as near to the water heater as possible and with no shut-off valve or other device between the heater and the expansion tank. Exception: In existing buildings with a closed water system, a properly sized pressure relief valve may be substituted in place of a thermal expansion tank. For closed water systems created by backflow protection in manufactured housing, as required in Section 890.1140(i), a ballcock with a relief valve may be substituted for the thermal expansion tank.
Bookmarks