M3
CONDENSING WATER BOILER
23
34-1115 12/15
8.2.4 Connecting to an Existing Vent System
Do not connect the M3 to an existing vent system, until it has been confirmed the existing vent system complies with
all requirements for a new vent system. A venting system in full compliance with the instructions provided in this
manual is required for safe and reliable operation of the M3. Do not connect the M3 to a masonry chimney.
WARNING: Before operating the appliance connected to an existing vent system, confirm the vent system
complies with all guidance and requirements for a new vent system specified in this manual. Failure to
confirm the existing vent system complies can result in unsafe operation and the potential for poisonous
carbon monoxide to enter occupied areas and can cause property damage, personal injury, exposure to
hazardous materials or death.
8.3 PVC Vent Installation
Follow the instructions below for installing schedule 40 solid PVC venting.
The stainless steel vent connection located near the rear of the boiler is 5-7/8” O.D., to accept 6 inch I.D. schedule
40 PVC pipe. After installing a short length of 6 inch PVC pipe to the vent connection, an increasing or reducing
fitting can be connected to adapt to a larger or smaller vent systems (See Section 8.2.1 Maximum Vent Length
(Equivalent Lengths).
1. Read and follow the information, instructions and warnings in “VENTING” section.
2. Do not insulate the plastic vent pipe.
3. Design the vent pipe route so that normal expansion (pipe getting longer) and contraction (pipe getting shorter),
due to on and off temperatures, does not bind or put stress on cemented pipe fittings.
4. A length of 6” schedule 40 PVC pipe must always be the first venting material attached to the M3, when using
PVC venting.
5. Dry-fit the length of 6” PVC pipe onto the M3 vent connector. Then remove the pipe and apply a liberal coating
of room temperature vulcanizing (RTV) adhesive to the outside of the vent connector and to the inside of the
plastic pipe. Before the RTV sets, slide the pipe over the vent connector while rotating approximately 1/8 of a
turn. Inspect and apply additional RTV to the joints, if needed to provide a sound air and water tight seal.
6. Drill a pilot hole through the PVC pipe and into the center of the stainless steel vent connector flange in three
equally spaced locations around the pipe. Drive stainless steel sheet metal screws through the pilot holes to
attach and firmly hold the plastic pipe onto the vent connector flange.
7. Clean and deburr all solid PVC pipe ends, then trial assemble the entire vent system vent before joining with
cement. Mark the pipe and fittings to identify their locations, then disassemble. Reassemble the vent system
using fresh PVC cement to connect the PVC pipe. If both solid PVC and solid CPVC pipe are used in the same
vent system, all joints between the two types of pipe must be made with fresh cement suitable for both
materials. Follow the cement manufacturer’s instructions for making sound air and water tight joints.
8. Vent support – The PVC vent system must be supported at intervals no greater than four feet, to prevent
sagging, distortion and stress on pipe fittings. Vertical pipe must also be supported to avoid stress on all
cemented pipe fittings and to prevent putting excessive weight on the appliance vent connection.
9. The vent pipe must be sealed at the point where it passes through a wall or roof, to prevent rain, insects or flue
products from entering the living space or interior of the building.
10. For proper vent operation and to protect the gas vent from wind and weather, attach a UL listed vent termination
to the outdoor end of the vent or otherwise provide suitable termination to prevent wind, water, debris or
animals from obstructing or entering the vent. Testing for leaks – Once the vent system is installed, it must be
checked to confirm all joints in the vent system are air and water tight. After the vent is assembled, close the
end of the vent with a taped plastic bag or some other temporary closure. With the gas supply turned off,
energize the M3 combustion blower to apply air pressure to the vent system. Spray each joint and vent
connection with commercially available leak detection liquid to confirm no air is escaping from any point. Repair
any leaks and retest. After testing is complete, de-energize the combustion blower, wipe clean the leak
detection liquid and REMOVE the temporary vent closure.
11. Do not use a barometric damper with the M3 venting system. Barometric dampers are designed for use with
certain Category I negative pressure vent systems. The M3 Category IV vent system operates with positive vent
pressure and will not operate safely with a barometric damper.
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