LAARS Mighty Therm VW-PW (Sizes 175-400) - Installation, Operation and Maintenance Instructions - Manual (Page 8)

LAARS Heating Systems
Page 8
supply or reverse the natural draft action of the venting
system. This could cause flue products to build up in
the heater room. More air must be supplied to make up
for the decrease.
2.5 Venting of Combustion Products
2.5.1 General Information
When installed indoors, the drafthood must be
connected to a venting system. The venting system
must be installed by a qualified installer and in
accordance with the latest edition of ANSI Z223.1. In
Canada, the installation must be in accordance with
CAN1-B149.1 or .2, and any local codes that apply.
The vent pipe must have a listed vent cap, and
extend at least 2 feet (0.6 m) above any object within a
10 foot (3.0 m) radius.
NOTE: Do not use sheet metal screws at the
snap lock joints of Type B double-wall gas vents.
Do not weld or bolt the vent pipe to the heater
drafthood. The weight of the stack must not rest on the
heater. The drafthood and heater top must be easily
removable for normal heater service and inspection.
WARNING
Avoid ending heater vents near air conditioning or air
supply fans. The fans can pick up exhaust flue
products from the heater and return them inside the
building, creating a possible health hazard.
Avoid horizontal runs of the vent pipe and 90
degree elbows, reductions, and restrictions. Horizontal
runs should have at least a 1/4 inch (6.3 mm) rise per
foot in the direction of flow. Support a vent connector
for the design and weight of the material used to
maintain clearances and physical damage and separate
of joints.
Always use double-wall or insulated vent pipe
(Type B or equivalent).
WARNING
In cold weather, uninsulated outside vents can chill
the rising flue products, blocking the natural draft
action of the venting system. This can create a
health hazard by spilling flue products into the
heater room.
Avoid oversize vent piping or extremely long
runs of the pipe which may cause too much cooling
and condensation of flue gasses.
When the installation of a power vent or draft fan
in the venting system is necessary, qualified personnel
should design the installation following good
engineering practices and all applicable codes. A
suitable draft switch must be wired into the heater
control circuit at the terminal designated Field
Interlock to keep the heater from firing unless there is
a positive draft.
2.5.2 Replacement of Existing Heater
When a heater is removed from a common
venting system, the venting system may be too large
for proper venting of the other appliances connected
to it.
If replacing an existing heater with a VW or PW
heater and the existing heater was connected to a
common venting system, the common venting system
must comply with ANSI Z223.1/National Fire
Protection Association (NFPA) 54. When resizing any
portion of the common venting system, the common
venting system should be resized to approach the
minimum size as determined using the tables in ANSI
Z223.1/NFPA 54, Appendix G. In Canada, the common
venting system should be resized so the installation
will be in accordance with CAN/CGA B149.1 or .2.
2.6 Water Flow
2.6.1 Reversible Water Connections
NOTE: This procedure is not recommended for
the PW pump-mounted models.
Laars ships the VW heater with the water
connections on the right side. The VW heater can be
installed with the water connections on either side. It
could be necessary, or helpful, to switch the
connections to the left side to improve access for
installation service. Have a professional service
technician perform this modification before installing
the heater using the following procedures:
1. Remove the front cover.
2. If there is a vent cap or drafthood installed, they
must be removed before removing the grate top
assembly. On indoor installations (sizes 175-
250), the drafthood switch must be disconnected
at the left side of the heater.
3. If the unit is in the low-profile outdoor
configuration, remove the hex-head screws
(see Figure 15) and lift the grate top assembly
straight up.
4. Remove the screws that fastens the flue collector
holddown clamps and remove the clamps (see
Figure 16).
5. Remove the flue collector assembly by lifting it
out of the chassis.
6. Remove the screws that fastens the gap closures
and put them aside.