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• Open first zone balance and purge or drain valve to let water flow out the hose. If zone valves are
used, open the valves one at a time manually. (NOTE: You should check the valve
manufacturer’s instructions prior to opening valves manually, so as not to damage the valves.)
• Manually operate fill valve regulator. When water runs out of the hose, you will see a steady
stream of water (without bubbles). Close balance and purge valve or drain to stop the water from
flowing. Disconnect the hose and connect it to next zone to be purged.
• Repeat this procedure for additional zones (one at a time).
For installation that incorporates standing iron radiation and systems with manual vents at the high points,
follow previous section and, starting with the nearest manual air vent, open until water flows out. Then
close vent. Repeat procedure, working your way toward the furthest air vent. It may be necessary to
install a basket strainer in an older system where larger amounts of sediment may be present. Annual
cleaning of the strainer may be necessary.
Upon completion, make sure that the fill valve is in the automatic position and each zone balance and
purge or shut off is in an open position and zone valves are positioned for automatic operation.
J. FREEZE PROTECTION FLUIDS
Use only inhibited glycol solutions which are specially formulated for hydronic systems. Ethylene glycol is
toxic and can attack gaskets and seals used in hydronic systems. Glycol mixtures should not exceed
1. Glycol in hydronic applications is specially formulated for this purpose, and includes inhibitors that
prevent the glycol from attacking metallic system components. Make certain that the system fluid is
checked for the correct glycol concentration and inhibitor level.
2. The glycol solution should be tested at least once a year and as recommended by the glycol
manufacturer.
3. Anti-freeze solutions expand more than water. For example: A 50% by volume solution expands 4.8%
in volume for a temperature increase from 32
o
F to 180
o
F, while water increases 3% over the same
temperature rise. Allowances must be made for this expansion in the system design.
4. A 30% mixture of glycol will result in a BTU output loss of 15% with a 5% increase in head against the
system circulator.
5. A 50% mixture of glycol will result in a BTU output loss of 30% with a 50% increase in head against the
system circulator.
It is highly recommended that you carefully follow the glycol manufacturer’s recommended
concentrations, expansion requirements, and maintenance recommendations (pH additive breakdown,
inhibitor reduction, etc.). Carefully figure the additional friction loss in the system as well as the reduction
in heat transfer coefficients.
K. ZONING WITH ZONE VALVES
1. Connect the boiler to the system as shown in Boiler Piping Details when zoning with zone valves. The
primary/secondary piping shown ensures the boiler loop will have sufficient flow. It also avoids applying
the high head of the boiler circulator to the zone valves.
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