D. SYSTEM PIPING
1. Figure 4.4 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. An alternate piping schematic for piping an indirect
water heater, such as the Peerless
®
Partner
®
, is
depicted in Figure 4.5. Note that, in this configuration,
the circulating pump for the indirect tank must be
sized to provide the minimum flow rate of the boiler.
In this configuration, both the GEN and CH
circulation pumps should be wired to the CH Pump
output on the terminal strip. This is required to
prevent the General (Boiler) pump from running when
a DHW demand is being satisfied. The total load of
CH and GEN pumps must not exceed 10 amps. If the
load is higher, then an isolation relay must be used.
3. The configuration illustrated in Figure 4.6 is for
multiple boilers. This figure shows an indirect DHW
tank in parallel with the heating zones. Notice that the
return to the boilers from the closely spaced tees in
the primary secondary arrangement is reverse return
to provide similar lengths of piping through each
boiler. This configuration shows the boilers in groups
of two to take advantage of the P
UREFIRE
®
PF-850 or
PF-1000 stacking capability.
4. Figure 4.7 shows a multiple boiler configuration which
uses zone valves instead of zone circulators. Systems
which combine both zone valves and zone circulators
can help to minimize electrical loads if there are small
zones in the system. Contact your PB Heat, LLC
representative for assistance with larger systems.
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.
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. Table
4.2 provides the water capacity of the heat exchanger
to help in system volume calculations.
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.
WATER PIPING & CONTROLS
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