System Piping; Freeze Protection - PEERLESS PureFire PF-80 Installation, Operation & Maintenance Manual

f. Table 4.5 provides a list of recommended
circulators for boilers on a secondary loop of a
primary/secondary system which uses water as a
heating medium.
g. Special consideration must be given if a glycol
based anti-freeze solution is used as a heating
medium. Propylene glycol has a higher viscosity
than water, therefore the system pressure drop will
be higher.
NOTICE
The circulator sizing given is for primary/secondary
installations only. The system circulators must be
sized based on the flow and pressure drop
requirements of the system.
11. Indirect Water Heater: An indirect water heater should
be piped to a dedicated zone. The P
provides electrical terminals for connecting a domestic
hot water (DHW) circulator. Examples of piping for
the indirect water heater are shown under subsection
"D", System Piping of this section.
D. SYSTEM PIPING
1. Figure 4.5 shows a single boiler with multiple heating
zones. In this case, the DHW zone is piped in parallel
to the heating zones on the primary loop.
2. For a single boiler with one heating zone and one
DHW zone which utilizes an indirect water heater like
the Peerless ® Partner
Figure 4.6. In systems like this, the DHW circulator
must be sized to provide the minimum flow rate
through the boiler.
3. In Figure 4.7 an additional boiler is added and more
heating zones are shown. Notice that the two boilers
are piped in parallel on the secondary loop. This
maximizes the efficiency of the boilers since the lowest
temperature system water is returning to both boilers.
4. Figure 4.8 shows a multiple boiler system with several
different types of heat distribution units. This system
illustrates how different temperature zones can be
supplied from the same source by blending supply
and return water to the zone.
5. In Figure 4.9 zone valves are used instead of zone
circulators. Notice that the system is piped using
reverse return piping to help balance the flow through
the zones. If the zone lengths vary balancing valves
are required on each loop.
E. FREEZE PROTECTION
1. Glycol for hydronic applications is specially formulated
for heating systems. It includes inhibitors which prevent
the glycol from attacking metallic system components.
Make sure that the system fluid is checked for correct
glycol concentration and inhibitor level.
2. Use only inhibited polypropylene glycol solutions of
up to 50% by volume. Ethylene glycol is toxic and
can chemically attack gaskets and seals used in
hydronic system.
F ® boiler
URE IRE
® , pipe the boiler as shown in
WATER PIPING AND CONTROLS
3. The anti-freeze solution should be tested at least once
per year and as recommended by the manufacturer of
the product.
4. Anti-freeze solutions expand more than water. For
example, a 50% by volume solution expands 4.8%
with a 148°F temperature rise while water expands
about 3% for the same temperature increase.
Allowance for this expansion must be considered in
sizing expansion tanks and related components.
5. The flow rate in systems utilizing glycol solutions
should be higher than in a water system to
compensate for decreased heating capacity of the fluid.
6. Due to increased flow rate and fluid viscosity, the
circulator head requirement will increase. Contact the
pump manufacturer to correctly size the circulator for
a particular application based on the glycol
concentration and heating requirements.
7. A strainer, sediment trap, or some other means for
cleaning the piping system must be provided. It
should be located in the return line upstream of the
boiler and must be cleaned frequently during the
initial operation of the system. Glycol is likely to
remove mill scale from new pipe in new installations.
8. Glycol solution is expensive and leaks should be
avoided. Weld or solder joints should be used where
possible and threaded joints should be avoided.
Make-up water should not be added to the system
automatically when glycol solution is used. Adding
make-up water will dilute the system and reduce the
ability of the solution to protect from freezing.
9. Check local regulations to see if systems containing
glycol solutions must include a back-flow preventer or
require that the glycol system be isolated from the
water supply.
10. Do not use galvanized pipe in glycol systems.
11. Use water that is low in mineral content and make
sure that there are no petroleum products in the
solution.
a. Less than 50 ppm of calcium
b. Less than 50 ppm of magnesium
c. Less than 100 ppm (5 grains/gallon) of total
hardness
d. Less than 25 ppm of chloride
e. Less than 25 ppm of sulfate
12. Check with the local water supplier for chemical
properties of the water.
13. The following test will determine if the water is of the
appropriate hardness. Collect a sample of 50% water
to 50% propylene glycol. Let the solution stand for 8-
12 hours shaking it occasionally. If white sediment
forms, the water is too hard and should not be used
to dilute the glycol.
14. Mix the solution at room temperature.
15. Do not use a chromate treatment.
16. Refer to Technical Topics #2a published by the
Hydronics Institute for further glycol system
considerations.
21