How to Vent A Rinnai Tankless Water Heater

How to Vent A Rinnai Tankless Water Heater

There are several models of gas-fired Rinnai tankless water heaters, and you should go over the manual to see the instruction for installing the vent on your unit.

We’re going to give you details about installing PVC/CPVC standard venting with a non-return flue check valve. Don’t forget that venting with PVC and CPVC must still comply with the requirements of the installation and operations manual.

How to install the vent on your Rinnai water heater?

There are several aspects to address when it comes to venting:

  • Installing the check valve

You have to begin by installing the check valve and connecting the valve adapter to the exhaust adapter ring. You must push the check valve adapter entirely into the Exhaust Adapter Ring.

Use two screws and drive one of them through the hole in the Exhaust Adapter ring. As for the other one, you need to screw it into the other side of the ring, using a 180degree angle and the same height as the first screw. Keep in mind that the Exhaust Adapter Ring doesn’t come with a preexisting hole on the backside.

  • Connecting the Exhaust Adapter Ring

Once again, you need to drive one screw through the front hole in the heater sheet metal and into the Exhaust Adapter Ring. The second screw has to go through the rear area of the sheet metal.

You have to put together the check valve by linking the parts. Make sure to connect the 3” PVC/CPVC mount to the Non-return Flue Check Valve. It’s also essential to apply the lubricant around the outer pipe diameter.

  • Attach the Check Valve to the Check Valve Adapter, and pour 8.5oz of clean water into the check valve. Remember that you also need to take the intake cap off for access to the intake airport
  • Install 3” PVC/CPVC into the check valve and intake airport, cutting pipe end square and gently.
  • Mount the self-tapping screw through the hole from the intake airport.

You can do the same for the PVC/CPVC conventional vent system.

What’s the best way to assemble the header?

There are different tips for different diameters of PVC/CPVC pipes:

  • 3” PVC/CPVC
    • It connects to two units, inline or corner
    • The header length should be 20.5″ center to center, whereas the maximum vent lengths are two units 40ft.
  • 4” PVC/CPVC
    • You can use it for two or three tankless units
    • Get the 3” PVC/CPVC and follow it with 4”x3” reducers
    • The header length is 20.5” center to center
  • 6” PVC/CPVC
    • It links two to five tankless water heater
    • You may utilize 3” PVC/CPVC at the unit and link to a 6” header through the use of reducers
    • The header length is 20.5” center to center

Is connecting the venting complicated?

Nothing is complicated when you follow the steps accurately:

  • Use the self-tapping screw for securing the check valve to the unit
  • Place the 3” PVC/CPVC straight inside the check valve
  • It’s better not to use any adhesive on the PVC/CPVS connection, but only the supplied lubricant. Glue could ruin the check valve and even void serviceability of the valve
  • Use reducers attached to 3” PVC/CPVC for 4” and 6” PVC/CPVC system
  • The slope horizontal will exist toward unit ¼” per foot. Never slope the combustion air pipe toward the tankless unit.
  • The horizontal support vent needs at least 4ft, whereas the vertical vent needs a minimum of every 6ft.

Here are the requirements for horizontal venting:

  • You need to end outside the building
  • The header length is 20.5” center to center
  • Support horizontal vent needs at least every 4ft. Whereas for the vertical is at very 6ft.
  • The exhaust and combustion air endings should have 12” and 20ft maximum separation

You should also check the requirements for vertical venting:

  • It has to end outside the building
  • The vertical support vent should run at least at every 6ft, whereas for the horizontal is minimum 4ft
  • The header length is 20.5” center to center.

What are the exhaust vent termination clearances?

In the case of direct vent applications, the terminations have to be mounted for collecting combustion air and eliminate exhaust.

Do you need to make adjustments for high altitude?

For the PVC/CPVC regular venting, you should make sure that the tankless water heater is installed correction so that you can use it at high altitudes. The high altitude installations are supposed to work fine up to 10,200ft for liquid propane and natural gas.

You should set DIP switches no.2 and no.3 in the first group of switching according to the altitude. The default setting is 0-2000ft with switches SW2 and SW3 in the OFF position. Once you adjust the DIP switch, you no longer need to change the gas pressure setting for the high altitude.

Do’s and Don’ts when installing the vent

There are several things to do related to installing the vent on your water heater:

  • The clearances have to be achieved, and the vent length has to be within the mandatory limits
  • The intakes and exhaust terminations have to vent outside the application
  • Vent length refers to additional venting, terminations, and fittings that are needed for accessing the outside of the building. It doesn’t include the header
  • The header length only consists of the venting ranges that are necessary for attaching several units spaced 20.5″ apart center to center
  • Here are the specs for the maximum equivalent vent length:
    • 90degree elbow means 10ft
    • 45 degree means 5ft
    • Tee termination means 10ft
    • Spacing higher than 20.5” center to center is vent length
    • Vent connections need to be linked together, forming an airtight seal
    • The combustion air intake has to be connected to the unit and secured with a self-tapping screw
    • Venting has to be direct and includes a minimal number of pipe fittings
    • You should adjust the temperature setting on the tankless unit
    • Try not to have sags or dips in the horizontal vent

Don’t forget that there are plenty of restrictions related to the vent installation:

  • Never mount in a different distribution system
  • Try not to combine vent elements from different manufacturers
  • Never connect the venting system with a current vent or chimney
  • Don’t install the water heater, venting, nor vent terminations in areas with corrosive compounds
  • Don’t cover a non-metallic vent pipe nor fittings with thermal insulation
  • Don’t use cellular core PVC, ABS, or galvanized material for the exhaust vent

The conclusion

Installing the vent for your Rinnai tankless water heater isn’t complicated when you follow the instruction in the manual. Should you feel overwhelmed by the job, it’s wise to get professional help, nevertheless.

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