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34000 Autry Street, Livonia, MI 48150 | 800.968.5530 | Fax 734.419.0209 | www.hamiltonengineering.com | LIT91110 REV 06/2018
CENTRAL HEATING
CENTRAL HEATING (CH) – Model prefix HWH
In these configurations the room thermostat reference can be a:
On/off—
Thermostat is connected and the input is closed. The flow setpoint temperature is determined by a heat curve.
The heat curve determines the flow setpoint temperature by using the temperature of S6 (outside)(terminals 1 & 2 or
9 & 10, 26 & 27 depending on model). When no outside sensor is connected (automatically detected), the flow setpoint
temperature is determined by the red wheel setting.
*Power being switched is 30 VDC. Connection is made at terminals 5 & 6 (or 13 & 14, 57 & 58 depending on model) (X1–9,18).
Note: if this circuit is not opened pump P3 will run all of the time except during a call for DHW. This circuit
should also be used for warm weather shut down, night set back etc.
OpenTherm—
Thermostat is connected and the input is closed. The flow setpoint temperature is determined by this
modulating thermostat utilizing the heat curve as described below in Outdoor reset. If no outdoor sensor is present, it is based
in setpoint. The thermostat sends the setpoint temperature to the FMT 914. Connection is made at terminals 5 & 6 (or 13 &
14, 57 & 58 depending on model);
this requires the use of the optional OpenTherm Bus, two wire communication board.
0-10Vdc—
Thermostat is connected. The flow temperature is determined by converting the input voltage to a flow
setpoint temperature. When the measured voltage is below 1-volt heat demand will end. Connection is made at terminals 7 & 8
(or 30 & 31 depending on model).
Outdoor Reset—
Boiler water temperature can be controlled automatically based on outdoor temperature if a 10k ohm
thermistor is connected to terminals 1 & 2 (or 9 & 10, 26 & 27 depending on model). The control will automatically sense
the presence of the sensor. When an outside temperature sensor is connected, the flow temperature will be set, in a
linear way, from the outside temperature, in accordance with the equation:
Tflow = (40 – Parameter Data) K + Z (°C)
It is adjustable with two levels of settings:
a) Installer level:
At this level it will be possible to change the angle of the heat curve, that is the K – factor (reset ratio),
plus the minimum water temperature
(p = 2 ET)
at the outdoor temperature you want heating to begin
(p = 2 EP)
.
Minimum water temperature should be based on the type of radiation used for heat distribution. To operate at this level,
you will need a laptop or PDA with the appropriate SIT software.
b) User level:
The user can adjust the boiler water temperature by a parallel shifting of the heating curve when
adjusting the red potentiometer wheel. This is the Z factor and has a programmable range from 0 – 20°C (36°F)
(factory default is 20°C 36°F), which allows for a + 10°C to a -10°C from center position adjustment.
Note: the maximum temperature setting (parameter 2EP) does not shut the boiler down, it sets the curve only!
Calculating required Parameter inputs:
1. Determine maximum outdoor temperature for specifying a corresponding water temperature.
2. Determine the minimum water temperature that will work at the above temperature.
3. Determine the design outdoor temperature of the heating system.
4. Determine the design water temperature to satisfy the radiation style at design air temperature.
Dividing the difference of the two water temperatures by the difference of the two air temperatures equals the “K” factor.
Factory Defaults
K = 1.4
Parameter 2 ES
Range 0 - 8
Z = red wheel position, + or – 18°F
from center point (12:00)
Parameter 2 EU
0 – 36°F range
Maximum outdoor temp. = 70°F
Parameter 2 EP
32 – 104°F range
Water temp at maximum air temp. = 70°F
Parameter 2 ET
32 – 140°F range
