34000 Autry Street, Livonia, MI 48150 | 800.968.5530 | Fax 734.419.0209 | www.hamiltonengineering.com | LIT91127US REV 5/2018
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MAINTENANCE
F. COIL ANTI-SCALING PREVENTION FEATURE
The EVO controller (FMT 914) contains sophisticated software that enables it to monitor the rate of temperature
rise through the heat exchanger. By doing this, it greatly reduces the possibility of heat exchanger failure due
to scaling or fouling. A set of parameters are programmed in at the factory, to provide a design temperature rise
(∆T) setting on each size unit that is fixed. The Anti-Scale is based on an increase over the design ∆T through
the heat exchanger. This Anti-Scale is determined using the inlet and outlet sensors, even if a tank thermistor
is being used. If the Anti-Scale setting is reached, the unit will display A8, shut down and not re-fire until it has
cooled. After the first three times this condition is reached in the FMT 914 reset life cycle (reset life cycle is the
time between factory service history downloads), the FMT 914 control will go into hard Lockout, display E6, and
have to be manually reset. After it has been reset, it will fire again, but at a maximum of 50% of rated input in
an attempt to prevent further damage but still provide some hot water. Once the heat exchanger has been acid
cleaned contact the factory for instructions on resetting the unit for full rated BTU input.
Typical causes for repeated E6 indications at start up are air trapped in the heat exchanger (be sure air vent cap
is loose) or contaminates lodging in the piping or heat exchanger during installation, both of these causes can
generally be cleared by isolating the hot water system and flushing water at full city pressure through the drain
valve or relief valve on the heater outlet.
Please note: Scale monitoring feature only available on HWD (water heater) models.