Grant Instruments FH16-D - Manual (Page 9)

Flow Heaters
Part No: 15630/Issue 3 Page March 2003 9
4.2 BS15 filler/de-aerator and bypass system
Good temperature control depends on an adequate flow through the flow heater. If narrow tubes
or small cells restrict flow, a bypass system is required. The bypass ensures that most of the
flow takes place in a large bore loop, with a smaller flow through the external circuit. The BS15
simplifies filling and de-aerating of closed systems; the top of the bypass chamber has a vent
hole to release trapped air and the whole top can be removed for filling. Connecting pipes for
the external circuit are 6mm o.d. connections to the flow heater are 15, o.d.
4.3 Pipe insulation PF2
PF2 foamed polyurethane tubing for insulating flexible pipes between flow heaters, coolers and
other equipment; supplied in 2 metre lengths 16mm internal diameter and 9mm wall.
4.4 Remote temperature probes: FH16-D
Remote, plug-in temperature probes may improve the accuracy of control or display by sensing
temperature in the external apparatus being controlled. Standard probes are fitted with two
metres of cable.
Special probes can be supplied for use in corrosive liquids.
4.4.1 The FF17 probe has a very fast response, with the sensing element at the end of a flexible
nylon probe 10mm long and 4.5mm external diameter.
4.4.2 The LL17 stainless steel probe is more robust but has a slower response. It is 125mm long
and 5mm diameter.
5 Fault diagnosis
Symptom Possible Cause Action Required
Unit does not operate Unit not switched on Switch on
Power lamp off Unit not plugged into power supply Plug in, switch on
Fuse blown in the unit or, for UK
units, in the plug Check and replace
Electrical power supply failure Check that other electrical
appliances on same circuit
are working
Alarm light on Overtemperature cut-out has
operated Reset cut-out as described in
4.6
Temperature does not
rise when expected Set temperature is lower than
liquid temperature
Check set temperature
Set temperature is too close to
ambient
Raise the set temperature or
fit accessory cooling
Temperature control circuit fault Have unit checked by a
competent person
Temperature
continues to rise
when not expected
Set temperature is higher than
liquid temperature
Check set temperature
Temperature control circuit fault Have unit checked by a
competent person
Pump does not
operate Pump obstructed Clear obstruction