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5.3 Charging the Fluid System
• The FireBird HD308, all hose and all accessories are
shipped pre-charged with the “approved blend” of
heat transfer fluid (HTF). The required fluid is a 50%
blend of Inhibited propylene glycol and de-mineralized
neutral PH (#7)water. This provides freeze protection
to -29ºF (-34ºC). The HTF provided with a new system
and accessories is marketed as DowFrost. Use of any
other product that cannot be proven to be equal in all
respects will void warranty of the system.
• Check the HTF level gauge (Fig. 32). The reservoir
should be 1/4 to 1/2 full when the system is cold.
Add approved fluid, if necessary, at the vented filler
cap (Fig. 32).
• Connect all primary hoses from the FireBird HD308 to
the distribution manifold.
• Place all fancoils in the desired locations and route all
the hoses to them OR lay out all hose grid circuits for
ground thaw or concrete curing.
• Connect hoses from the manifold to ONE fancoil ONLY.
• Open 2 HTF circuit valves (Fig. 33).Turn ON the
circulating pump switch (Fig. 12) and let the fluid
circulate until all the air is eliminated from the first
branch circuit. Air has been purged when steady
pressure of 30 to 35 PSI is observed at the glycol
pressure gauge (Fig. 25).
27: Layout for Fluid Distribution
1. Central Hydronic Heating Unit
2. Burner& Heat Exchanger
3. Circulating Pump
4. Reservoir for Expansion & Filling
5. Primary Fluid Hoses, 1”
6. Secondary Fluid Hoses, 3/4” or 1”
7. Manifold for Multiple Connections
8. Fancoil Heat Exchanger
9. Heat Transfer Coil
10. Air Moving Fan
11. Heated Supply Air
12. Intake Air
29: Fancoil Connected to
HD308 Unit
28: Hoses Connected to
HD308 Unit
30: Manifolds for Fancoils - Supply & Return
32: HTF Level Gauge & Vented Filler Cap
33: HTF Circuit Valves, Y-strainer
& High Temp. Limit