Instruction manual
17
P/N HN-IOM-1 82-0331 Copyright 2009 Mestek, Inc.
Finned copper tube gas boilers & water heaters – Control manual
Configuring for DHW applications (continued)
5
DHW Method 1 —
DHW tank sensor
(on DHW Sensor terminals)
DHW tank temperature controlled directly
❑ — tank
temperature sensor (10k thermistor) in tank connected to
DHW TEMPETURE SENSOR input (J10B 1/2) —
see Figure 4, page 23 for location.
Single or multiple boiler application ❑ .
Dedicated water heating or combined space heat- ❑
ing and DHW.
Limiting maximum boiler temperature when
applying for DHW applications —
When the
boiler is to be used for domestic water heating,
jumper JPS1 must be clipped. is limits the
maximum water outlet temperature. Failure to
comply could result in overly hot water being
delivered to the system. See Figure 3, page 22 for
location of JPS1.
Method 1 operation
Method 1 regulates 1 or more boilers using three parameters
that are set in the DHW Setup menus — DHW SETPOINT
and DHW DIFF, and ADD BOILER DELAY.
DHW SETPOINT — is is the target tank water temperature
(usually the maximum allowable temperature in the tank).
DHW DIFF — is is the control range for ring the boiler or
boilers (typically set at 5 °F for this method). NOTE that a nar-
row dierential seing may cause frequent cycling.
OFF TEMP (= SETPOINT)
All boilers are o when tank temperature is at or above SET- ❑
POINT temperature.
ON TEMP (= SETPOINT minus DIFF)
Boilers are brought on one at a time, and only when the tank ❑
temperature is below ON TEMP.
Boilers are added if temperature remains below ON TEMP. ❑
e HeatNet control waits for the ADD BOILER DELAY
time between each boiler.
When temperature reaches ON TEMP or above, no more ❑
boilers are added.
OPERATING BAND
Active boilers remain on until the temperature reaches the ❑
SETPOINT.
Method 1 post purge option
When tank temperature reaches OFF TEMP, all active boilers
turn o. e master boiler DHW relay will remain on for the
POST PURGE time set in the DHW Setup menu.
DHW post purge allows dumping the residual heat in the boiler
to the DHW tank.
Post purge will increase tank temperature
above SETPOINT —
Adding additional heat to
the DHW tank aer the setpoint temperature is
reached will increase tank temperature ABOVE
setpoint. Ensure that this is acceptable. IF NOT,
then the pump post purge must be disabled (set
to zero).
Method 1 setup procedure
Tank sensor ❑ — Install a 10k tank temperature sensor in
the tank. Wire the sensor to master boiler DHW SENSOR
terminals, J10B terminals 1/2 (Figure 4, page 23).
Clip jumper JPS1 ❑ (see Figure 3, page 22 for location) on
all boilers that will be used for DHW.
Header sensor ❑ — For combined space heating/water
heating — Install a header sensor and wire it to the master
boiler HEADER SENSOR terminals, J10A terminals 7/8
(Figure 4, page 23).
DHW pump ❑ — Wire the DHW pump relay or valve to the
normally-open contact, DHW PUMP/AUX. STATUS ter-
minals, J13 terminals 9/10 (Figure 3, page 22).
Master boiler setup ❑ — Navigate to the SETUP / DO-
MESTIC HOT WATER menu.
For DHW BOILER? enter NO (will be changed to a.
YES only aer other parameters are set).
Set the desired values for DHW SETPOINT, DHW b.
DIFF and ADD BOILER DELAY.
Enter YES for USE SENSOR?c.
For DHW PRIORITY?, select YES if the space heating d.
system pump is to be turned o during DHW heating.
Select NO if the space heating pump is to continue run-
ning during DHW.
Select the desired POST PURGE time (how long the e.
DHW pump or valve will remain open aer the boilers
have shut down). See previous WARNING regarding
pump post purge operation.
DHW MASTER?f.
Dedicated DHW — select YES so the master boiler will
control itself plus HeatNet member boilers.
Combined space heating/DHW — Select NO for
combined space heating/DHW systems. e master
boiler for a combined system will have a header sensor
connected for space heating. is will automatically
make it the master for both space heating and DHW.
Go to DHW BOILER? and select YES. Note that, if g.
jumper JPS1 has not been cut, the display will show a
message to do so.
If DHW operation is to be handled by a single
member boiler of a multiple boiler system, install
necessary piping, including diverting valve if
needed, and set up the boiler’s control seings to
switch to DHW on call from the tank sensor.