LAARS HEATING SYSTEMS
Page 8
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.
2E-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.
2F. Water Flow
2F-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.
7.
Remove the three grommets.
8.
Remove the drain valves and plug. There is one
hex plug on the left side, near the rear of the
jacket. The drain valves are located on the left
side and right side of the heater (see Figure 9).
9.
Remove the four screws that fastens the metal
channels covering the capillary tube on the right
side of the jacket, and lay the channels aside.
10.
In the control compartment, find the manual reset
high-limit switch box (see Figure 15) and loosen
the screw on the top to remove the cover.
11.
Loosen the screw that fastens the white wire and
remove it from the terminal. Pull it out through
the top of the case and separate the other white
wire from the red wire coming from the fuse
holder. Gently pull the two white wires out of the
control compartment and coil them on top of the
heat exchanger.
12.
A temperature control sensing bulb is located in
the front of the header on the inlet side and a
manual reset hi-limit sensing bulb is located on
the back side of the header on the outlet side (see
Figure 17). Remove these sensing bulbs from the
header. The following steps for removal apply to
all sensing bulbs:
a. If there is more than one capillary tube coming
out of the header, label the capillary tubes.
b. Loosen the screw on the capillary tube
retaining clip, then gently pry the clip apart
until it comes free from the temperature
control (see Figure 18).
c. Pull the sensing bulbs out of the temperature
control.
d. Gently pull the capillary tubes into the control
compartment.
e. Pull the temperature sensing bulb out of the
header, and temporarily route it to the front of
the heater.
