performs well at the normal 0.5% dosage rate.
Firing the boiler during a power flush
Q. What about firing the boiler whilst carrying out a
power flush?
A. By all means fire the boiler if you can – most chemical
reactions will proceed faster with some heat, and
also, when you come to put the full flow through each
radiator in turn, it’s useful to be able to feel whether
the radiators are heating up across the whole area, or
whether they have cold areas / panels. If they do, then
you can give that radiator extra attention.
A CLEARFLOW pump will handle water temperatures
above 70
o
C. We suggest firing the boiler for up to fifteen
minutes, but there’s no need to leave the boiler firing
continuously.
If you do fire the boiler, remember that when you switch
it off, the heat exchanger is still very hot, and continues
transferring heat to the water circulating through it, and
to the Clearflow pump. If you can’t keep your hand on
the pump tank, switch the boiler off.
If the boiler is non functional, or being replaced, then
you won’t be able to fire it anyway. If you’re using a
powerful chemical such as Powerflush FX2, you’ll still get
a good result even if you can’t fire the
boiler.
The alternative is to use a Kamco
CombiMag Dual Digital combined
power flushing magnet and heater,
with a 3kW electric heater. This is
inserted in one of the flow or return
hoses.
Q. I have a combination boiler system to power flush
but the boiler won’t fire - what can I do?
A. Persuading a combination boiler to fire can be difficult
because the low pressure limit switch senses a lack of
pressure, and prevents the boiler from firing.
1. Remember that when your power flushing pump is
connected into the heating, the maximum pressure you
will find is at the output of the pump impellor, or in more
practical terms, where your inlet hose connects into the
system. From that point on the pressure is falling away
throughout the system until the point where the return
hoses drops the water back into your power flushing
pump tank, where the pressure is again zero.
If you’re using a Kamco CP2 adapter to get connected
into the heating system, your power flushing pump will
be close to the boiler. Consequently if you set the flow
reverser handle so that the water flow is immediately
into the boiler rather than heading out into the radiator
circuit, you’ll be putting 1 bar+ pressure into the boiler
and a combination boiler should fire up.
If you’re not sure of the flow direction, just try with the
flow reverser lever in either direction.
Note: the current Kamco CF40 Evolution and CF90
Quantum were ‘tweaked’ when we designed them to
give extra pressure to help in this situation.
2. If the above doesn’t work, try partially closing the
Clearflow valve on the return side of your pump. By
reducing the cross sectional area, you will automatically
increase the pressure. Flow rate will be decreased, and
so only leave the valve partially closed whilst firing the
boiler. Once you have the water warm, shut off the boiler
and fully open the Clearflow valve for the normal high
flow rate needed for effective power flushing.
3. Here’s another suggestion.
If you’re flushing a combination boiler system that has
been in use for a while (not a new boiler), and you have
connected your power flushing pump into the system
across the copper tails of a radiator, this should work.
You could make up a temporary valved manifold and
loop out the power flushing pump by closing the two
valves in the flow and return hoses and opening the
valve in the bypass between the hoses.
You now have a temporarily completely closed circuit,
and so re-pressurise this the normal way, and then fire
up the boiler until you have the system water good and
hot. When you’ve got it up to temperature, shut off the
boiler and use the valved manifold to put your power
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