1) Can
I fit a cab heater or demister to my vehicle?
Your
vehicle's alternator should have a minimum rating as below, in order to ensure that the electrical draw of the heater
or demister is well below the system capacity:
600W
cab heater: 60 Amps
800W demister:
75 Amps
1000W demister:
90 Amps
Most modern buses
have alternators rated at 90 Amps or more.
You
also need to ensure that there is a clean, accessible power distribution point (e.g. battery terminals, main fuseboard studs).
Any intermediate cables between the battery and power distribution studs must be at least 6mm2 cross-sectional
area.
2) Can I run a heater or demister
with the engine off?
Although, for example,
the 600W cab heater draws about 22 Amps, which will in theory take nearly two hours to completely discharge a 40Ah battery,
the rating usually means 40 hours at 1 Amp discharge. The battery Ah rating will be much lower for higher currents. Also,
vehicle batteries are not designed for complete discharge, and will deteriorate after only one or two deep discharge cycles.
We therefore strongly recommend that the engine is running when the heater or demister is operating, and that
the off/on switch is linked to the alternator 'on' signal, or at least the ignition 'on' signal.
3) Do you make a 1000W cab heater?
Our demister unit (800W or 1000W) can also be used as a cab
heater.
4) Why can't the heaters deliver
more than 600 to 1000 Watts?
In principle
we could design any heat output wattage. However, limitations are imposed by the electrical power normally available, and
the current rating of standard cables and connectors.
We consider that 1000W (1kW) is the practical upper limit, equivalent to 40 Amps at 25V.
5) How much heat do I need?
Generally, our 600W cab heater
has proved to be satisfactory when used as the only heater in a small enclosed
cab, for example on a crane or forklift. It was originally designed to reduce the cab warmup time on buses and coaches,
and works best as an auxiliary heater for eliminating cold spots in the driver's footwell. For comparison, it puts out
about the same amount of heat as 1 metre of convector, or 'Finrad' type heater.
Our demisters (800W and 1000W) are capable of clearing a large proportion
of the screen, and provide some reflected warmth back to the driver. Also,
they can be effective cab heaters when mounted near the cab floor.
We would be happy to discuss which option suits you best.
6) How long does it take to install a cab heater or demister kit?
Depending on the layout of the vehicle cab and electrical system, it should be possible to install a kit in 2 to
3 hours.
7) Can anyone install a kit?
Installers should be competent and experienced in automotive
electrics. If you are unsure, please contact us.
8) Are any special
tools required?
Because high currents can
create hot-spots at poorly crimped terminals, we insist that all electrical connections are made with the correct tools. Kits
include a sample crimp to illustrate good practice.
Wire stripping must not be done with knives or
plier-type strippers.
Crimping must
not be done with pliers or cheap, non-ratchet tools.
Professional auto electricians should already have suitable
strippers and crimpers.
Alternatively, we
can supply approved tools.
9) Can I connect
the heater harness to any cables on the vehicle?
Almost
certainly not. The cables would probably not have a high enough current rating, and would burn out.
Always connect to the battery or main power distribution studs.
10) Can I specify a longer harness length?
Yes, please contact us if you require a longer harness ( Standard
lengths are 3m for cab heater, 4.5m for demister ).
Alternatively, you can extend a standard harness using cables of 1.5mm2 cross-sectional area.
We recommend connecting with additional crimp tabs and receptacles
rather than butt splices.
11) Why are
relays used?
Dash switches are not rated for
the current draw of a heater or demister. All the current passes through suitably rated standard automotive relays.
12) Do I need to buy any additional parts?
We supply the heater/demister as a complete kit including the
harness, relays, fuses, illuminated dash switch, connectors and mounting screws, so there should be no requirement for additional
parts. We can also supply alternative switches, and longer harnesses if required.
13) What does PTC stand for?
Positive Temperature Coefficient.
As the element gets hotter, its electrical resistance increases
dramatically, so that it self-limits its upper temperature to about 180°C.
This means that in the event of fan failure or blocked airflow, there is no fire risk.
14) Do you stock spare parts?
Yes, we do. We also offer a competitive exchange/refurbishment service.
15) Do you make a 12V cab heater or demister?
We have produced 12V 'specials', but there are two main issues which make 12V heating more difficult than
24V heating:
a) For the same heat output, you need twice the current at half the voltage (Watts = Volts X Amps).
This means that the cables, connectors and relays need
to be uprated and therefore more expensive.
Alternatively,
the heat output can only be half that at 24V if standard connectors, cables etc. are used.
b) 24V vehicles
generally have large alternators, rated at 90 Amps or more, generating around 2000W of available power. In contrast, most
12V vehicles have an alternator rated at around 500W.
As a rule of thumb, we prefer
to limit the current draw of our heaters and demisters to no more than 50% of the alternator output, to leave power available
for lights, wiper etc.
For these reasons,
we would not normally offer a 12V heater or demister with an output of more than 300W.
