4
DO provide sufficient cross sectional area in the pro-
cess piping connections equivalent to the system
pipes. In order to prevent undue pressure drop, maxi-
mum velocity in all piping should be less than 10 feet
per second.
DO check all vent tubes, purge valves, and bypass re-
lief valves at least once a month. Blocked vent tubes
may cause excessive system pressures and/or an ex-
plosion.
DO retighten all bolted connections and joints at oper-
ating temperature. Joints will expand and leak as they
get hot. Check all threaded connections on controls,
gauges, etc. for leaks.
DO vent all systems operating at atmospheric pressure
properly. Vents must be rigid metal piping terminating
outside the building or into a suitable container. The
vent line should never be made of plastic, rubber or
other low temperature material and should match the
vent port size on the expansion tank.
DO NOT use process piping connections smaller than
the pipes used in the system.
DO NOT use Magnesium bed or porous insulations
which can absorb fluid. When soaked, these insula-
tions will decrease unit efficiency and may cause a
safety hazard for personnel.
DO NOT permit leaks of any heat transfer fluid to con-
tinue unattended. Periodic inspection of piping and in-
sulation is essential.
DO NOT insulate expansion tank lines or the expansion
tank. These components must be kept cool and below
130°F (54˚C) for most heat transfer fluids.
DO NOT insulate flanges, valves or other connections
which may leak without being observed.
DO NOT use screwed pipe connections on any piping
over 1 inch diameter. Use flanges for connections with
composition gaskets.
Fluid saturated insulation on piping may cause
a safety hazard for personnel. Repair leaks and
replace soaked insulation immediately!!
Relief Valve Installation
The MWS can be operated with water and glycol/wa-
ter liquid combinations. Varying combinations of fluid
produce different boiling points and various pressures.
See Tables 1 and 2 as examples.
Table 1 - 100% Water
Temp. (˚F)
Pressure
(PSI)
Temp. (˚C)
Pressure
(bar)
200
0
93
0
220
3
104
0.21
240
10
116
0.69
260
21
127
1.45
280
35
138
2.41
300
52
149
3.58
Table 2 - Ethylene Glycol / Water Mixture
% Glycol
Mixutre
Boiling
Point (˚F)
Boiling
Point (˚C)
0
212
100
20
216
102
40
220
104
60
232
111
80
260
127
100
386
197
PLEASE NOTE: The charts are examples only! The
user must review and completely understand the fluid
properties chosen and the operating limits to be used
in the heating system.
Operating at temperatures above the boiling point of
the heat transfer fluid WILL PRODUCE PRESSURE in
the system. Systems that operate above the boiling
point MUST HAVE A USER INSTALLED RELIEF VALVE.
The MWS has provided a 3/4” NPT connection in the
outlet line for this purpose. Another user installation
port may be used, provided there are no shutoffs or
restrictions between the pressure chamber and relief
valve.
If an optional relief valve was not ordered from the fac-
tory and the units is operating over the boiling point of
the heat transfer fluid, the user MUST INSTALL AN AP-
PROPRIATELY SIZED RELIEF VAVLE to avoid damage
to the system and to avoid a potential safety hazard for
personnel. Any other installed equipment in the pro-
cess loop should also be adequately sized to handle
the pressure developed during such operation.
Systems that operate over 15 psi are recommended
to be ASME designed & certified. Please check local
codes for requirements.
Units that will be operating 20˚F (11˚C) below the fluid
boiling point will only have atmospheric pressure on
the system and will only need to plug the 3/4” NPT
outlet connection in the outlet line.
