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Antifreeze solutions expand more than water. For example, a
50% by volume solution expands 4.8% for 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.
4. The flow rate in systems utilizing glycol solution
should be increased compared with a water system
to compensate for increased heating capacity.
5. 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.
6. 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 solution is
likely to remove mill scale from new pipe in new
installations.
7. 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 a glycol solution is used. Adding
make-up water may significantly dilute the system.
8. 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.
9. Do not use galvanized pipe in glycol systems.
10. Use water that is low in mineral content and make
sure there are no petroleum products in the solution.
11. Mix solution at room temperature.
12. Do not use a chromate treatment.
13. Do not use glycol solution in a system that may
reach temperatures above 250°F.
14. Refer to Technical Topics, #2a published by the
Hydronics Institute Division of GAMA for further
glycol system considerations.
F. SPECIAL APPLICATIONS
1. If the boiler is used in conjunction with a chilled
medium system, pipe the chiller in a separate
secondary loop.
a. Assure that the boiler circulator is disabled during
chiller operation so chilled water does not enter
the boiler.
b. Install a flow control valve (spring check valve) to
prevent gravity flow through the boiler.
c. See figure 3.8 for recommended system piping.
2. For boilers connected to heating coils in a forced air
system where they may be exposed to chilled air
circulation, install flow control valves or other
automatic means to prevent gravity circulation of the
boiler water during cooling cycles. See figure 3.9 for
illustration.
WATER PIPING AND CONTROLS