Installation, Start-Up, Adjustment and Maintenance Manual
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Inhibited Propylene or Ethylene Glycol added to the water changes its thermal-physical properties,
particularly its density, viscosity and mean specific heat. Graph 2 gives the correction factors for the
hydronic system’s pressure drop as a function of glycol percentage added to the water. The graph is
accurate for water temperatures between 45°F and 55°F. It is important to consider the correction
factor for the sizing of the water pipes and water circulation pump. For the unit's internal pressure
drop, refer to Graph 1. Example: Total System Pressure Drop x Glycol Correction Factor = Actual
Total System Pressure Drop.
Graph 2
– PRESSURE DROP CORRECTION FOR GLYCOL CONCENTRATION
6.3 GAS PRESSURE ADJUSTMENT
The manufacturer supplies the units already adjusted for a particular type of gas. The type of gas can
be checked and easily identified by looking at the rating plate on the side of the unit. Nevertheless,
before starting the unit it is necessary to check and adjust if necessary the gas input to the burner.
Using the table below, locate the proper manifold pressure according to the local gas heating value
(BTU content per cubic foot) and specific gravity. This table is based on the correct natural gas input
for the model by manifold pressure in inches of water column (in WC).
BTU CONTENT
SPECIFIC GRAVITY OF NATURAL GAS
PER CU. FT.
.55
.6
.65
.7
950
3.2
3.6
3.9
4.3
975
3.0
3.3
3.7
4.0
1000
2.8
3.1
3.5
3.8
1025
2.6
3.0
3.3
3.6
1050
2.5
2.8
3.1
3.4
1075
2.3
2.6
2.9
3.2
1100
2.2
2.5
2.7
3.0
1125
2.0
2.3
2.5
2.7
Table
12
- MANIFOLD PRESSURE BASED ON GAS INPUT OF 96,500 BTU/HR USING 1113 ORIFICE.
The conditions referred to by the table above are for the guidance of the installer and the CSA design
certification does not cover the conditions described therein.
Note: For Propane Gas Models, follow the same instructions as given below for natural gas. The
manifold pressure for propane gas should be 10.0” W.C. and adjustment is made at the gas valve
regulator. Manifold pressure at 96,500 Btu/Hr. input using 1133 orifice.
0.96
0.98
1.00
1.02
1.04
1.06
1.08
1.10
20
30
40
50
PERCENTAGE OF ANTIFREEZE BY VOLUME
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