5
Boiler/chiller interlock
A volt free normally closed circuit is provided as a boiler/chiller interlock. The circuit has 1 high pressure
contact and 1 low pressure contact either of which, when operating, will open the boiler/chiller circuit. If the
high pressure contact is not required with chiller applications it can be omitted. See product wiring drawing.
Operation
Ensure MCBs in the electrical section are at the on position, switch selector switch on front panel to Auto.
Switch main isolator on front door to the on position. The digital display will now go through the starting
check sequence, after about 8 seconds the display will show system pressure.
If the system pressure is lower than the fill pressure then a pump will run and start to raise the
system pressure. Once the system pressure is restored the pump will stop.
If the pressure in the system falls to the duty pump cut in point the duty pump will start, once the system
pressure has been restored the duty pump will stop. Each time the pressure falls the alternate pump (on two
pump units) will start and restore system pressure. If the duty pump after running for 2 seconds
has not succeeded in raising the pressure and it continues to fall by 0.2 bar it will be deemed
that the duty pump has failed. The failed pump will then be locked out and the standby pump
will run and take the place of the duty pump.
If a pump trips for any reason it will be locked out and the standby pump will operate in its place.
Once the reason for pump failure has been ascertained and rectified the selector switch can be switched to
the off position and back to auto to reset the controls.
Maintenance
Routine check (3 monthly intervals)
1. Check that the pump seal is not leaking.
2. Check the pump is not seized and develops the correct pressure.
3. Check that the pump operates without undue noise or vibration.
4. Check that the motor runs without overheating.
Routine check (6 monthly intervals)
1. Check the break tank is clean and that the correct water level has been maintained.
2. Check that all screws are tight on electrical components.
3. Check that the earth connections are tight and making good contact.
4. Check that the gas pre charge is at the correct pressure, this should be done by isolating the unit from the
System and draining water back into the break tank by opening one of the 4mm ball valves (see drawing
for location) once the unit pressure has been discharged, a tyre gauge can be connected to the pre
charge valve to display the vessel pre charge pressure. Recharge as necessary with Nitrogen or dry air.
All other expansion vessels connected to the system can be checked in the same manner.
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