Model CFC ClearFire Commercial Boilers
28 Rev. 05-2012
2) The glycol concentration determines the maximum allowable firing rate and output
of the boiler(s). Please refer to the firing rate limitation and corresponding high fire
speed settings vs. glycol % in the charts below.
3) Maximum allowable boiler outlet/supply temperature: 185 deg F (85 deg C).
4) Minimum water circulation through the boiler:
a) The minimum water circulation must be defined in such a way that the
temperature difference between the boiler outlet/supply and inlet/return is a
maximum of 40 deg F (22 deg C), defined as DT (Delta T). A DT Limit
algorithm should be enabled in the boiler controller.
b) Independent from the hydraulics of the heating system, constant water
circulation through each boiler is required. (Requires a dedicated boiler
pump if in a primary/secondary loop arrangement.) Refer to table below for
minimum boiler circulation rates.
5) Minimum over-pressure at the boiler:
For outlet temperatures up to the maximum of 185 deg F (85 deg C), a minimum
operating pressure of 30 psig (2.1 bar) is required.
6) pH level should be maintained between 8.3 and 9.5
Table B5-18. Glycol Application Guidelnes - Model CFC
Minimum required boiler circulation rate (gpm) at maximum firing rate.
ClearFire System ΔT (˚F)
Model-Size ΔT = 10˚ ΔT = 20˚ ΔT = 30˚ ΔT = 40˚
CFC-500 88 44 29 22
CFC-750 131 66 44 33
CFC-1000 175 88 58 44
CFC-1500 263 131 88 66
CFC-1800 316 158 105 79
CFC-2500 438 219 146 110
CFC-3300 578 289 193 145
Notes/Limitations:
1. Maximum firing rate determined by ClearFire CFC - Glycol Firing Rate Limitation chart (below).
Maximum high fire blower speed should be set according to chart.
2. Glycol concentration limit of 25%-50%. Minimum required system operating pressure is 30
psig.
3. Maximum system operating temperature of 180 ˚F. Maximum ΔT of 40˚.
4. Circulation rates correlate with boiler output based on 92% nominal efficiency.
5. Standard altitude (<1000' ASL). Contact C-B for high altitude applications.
6. Pumps should be sized based on system design ΔT and minimum required flow rates.
7. At minimum firing rate, the minimum circulation rate should correspond to the boiler's turndown.
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