Gas Type Selection
The boiler comes from the factory setup for natural gas. The
boiler comes with a conversion kit that must be used if the
boiler is to be installed and fired with propane gas. Instruc-
tions for the conversion of the boiler are located in the instal-
lation and maintenance manual.
Mounting the Boiler
The boiler bracket should be securely fixed to a wall that is
sufficiently strong enough to bear the weight of the boiler
when filled with water as well as the attached plumbing. The
boiler should not be used to support the plumbing system,
all piping attached to the boiler must be properly supported
with appropriate support brackets. Do not install the boiler
on drywall unless anchoring directly to the studs. Install the
boiler bracket to the wall with the provided mounting materi-
als. Ensure that it is level before hanging the boiler.
Gas Piping
The boiler gas piping must be sized to accommodate the full
load of the boiler in addition to all the other gas appliances
in the building. The boiler should be the first appliance con-
nected to the gas supply line. Never use a ½” corrugated
appliance adapter for connecting the boiler. If using propane
contact your propane supplier to size gas piping, tanks, and
100% lockup gas pressure regulator. Install a manual gas
shutoff valve below the boiler following all local and national
code.This valve should be a full port gas ball valve. Install a
drip leg/sediment trap as well as a union to facilitate servicing
of the unit. See the installation and maintenance manual for
complete instructions. The nominal natural gas pressure is
7” W.C. The nominal propane gas pressure is 11 W.C.
Water Piping
The heating system should be flushed before fitting the boiler
to the system, see the installation and maintenance manual
for system flushing instructions.
The boiler must be connected to the heating system utilizing
primary secondary piping to hydraulically separate it from
the system. Piping can be accomplished in two ways either
through the use of a Low Loss Header (LLH) or through
Closely Spaced Tees (CST). When using a low loss header
please refer to the header manufacturer for sizing and instal-
lation information. When using closely spaced Tees they
must be sized and pipe according to standard design prac-
tices based on the btu output of the boiler and the flow rate.
Follow the two piping illustrations below for valve and pump
placement. The PRV must be installed directly below the
boiler before any shutoff valves. Install unions as shown in
the drawing as well as ball valves for boiler isolation to allow
for service and maintenance of the boiler. Important:
Primary boiler loop piping must be a minimum diameter for
each model
VSL II-90: 1"
VSL II-150: 1" 1/4"
VSL II - 200: 1 1/4"
VSL II - 250: 1 1/2"
Primary Secondary Piping:
Primary secondary piping must be used at all times with this
boiler. Failure to properly size and install primary secondary
piping may cause damage to the boiler and void the war-
ranty. There are two standardized methods for primary sec-
ondary piping, the first is to use Closely Spaced Tees here
after referred to as CST. The second method is to use a third
party Low Loss Header also called a Hydraulic separator.
Slant/Fin VSL II Quick Start Guide 3
Figure 2. Mounting boiler Illustration
Figure 1. Service clearances
