Install Instructions

55
IM-PR 566442 1114 (Design Manual)
1.11.2.4 Glycol expansion tank selection
Glycol solutions require larger expansion tanks than
100% water solutions. Expansion tanks for glycol
solutions are typically at least 1.2 times the size of
those required for 100% water solutions. To size an
expansion tank for a glycol solution, use the same
equation that you would to size a 100% water
solution. When using the following equation to size
an expansion tank for a glycol solution, be sure
to use the appropriate densities of the % glycol
solution based on the type of glycol (i.e., propylene
or ethylene), and the values provided in Table 1-16
and Table 1-18.
V
t
= V
s
(
D
c
D
h
) (
P
rv
+ 9.7
P
rv
- P
a
- 5
)
•
•
-1
Vt = minimum tank volume (gal)
Vs = fluid volume in system (gal)
Dc = density of the fluid at its initial start
temperature (lbs/ft
3
), whether water or glycol mix
Dh = density of the fluid at its maximum operating
temperature (lbs/ft
3
), whether water or glycol mix
Pa = air side pressurization on the opposite side of
the bladder, typically set at 12 psi from factory (psi)
Prv = pressure relief valve setting in (psi)
Supply
Temperature
Control Method
Supporting
Hardware
Flow Zoning
Fixed
Thermostat (standard or
programmable)
• Thermostatic
mixing valve
• Dedicated heat
source
• Hydronic mixing
block
Fixed – Single speed
circulator(s) with
bypass
• Powerheads
• Pumps
• Zone valves
Variable – Variable
speed circulator(s);
no bypass required
Variable
Thermostat (standard or
programmable) with:
• Outdoor reset and/or
• Indoor reset
• Mixing valve
• Diverting valve
• Injection mixing
• Modulating heat
source
• Hydronic mixing
block
Fixed – Single speed
circulator(s) with
bypass
Variable – Variable
speed circulator(s);
no bypass required
Table 1-27 Control options and methods for radiant heating systems
1.11.3 Glycol system maintenance
Glycol solutions should be checked each year
using a suitable refractometer to determine
glycol concentration. Check the concentration
of corrosion inhibitor periodically, following
procedures recommended by the glycol
manufacturer. Typically, glycol manufacturers offer
a maintenance service for a reasonable cost.
1.12 Controlling the system
While the sizing of a heating system is based
on design day conditions (i.e., full-load), heating
systems are required to operate at part-load
conditions for over 90% of the heating season.
Additionally, modern systems are typically called
upon to deliver water to separate zones at different
supply temperatures. To maintain comfortable
conditions throughout a building regardless of the
instantaneous heat load, it is imperative to specify
a well-designed control system. Designs may
incorporate fixed or variable temperatures, fixed or
variable flow, and multiple zoning options.