On Tue, 26 May 2009 16:54:14 +0100, Dave Osborne wrote:

Call Redring (Applied Energy Products) technical help line on 08709
000430

http://www.applied-energy.com/en/contact

Haven't looked at the Heatrae products but noticed that Redring are pretty
keen on you only fitting their own taps or shower fittings to their
heaters. I've just been dealing with another make and model of this type
of heater which has been giving problems because it is prone to tripping
its overheat cutout thermostat. Resetting this involves opening up the box
so it's a hassle for the user. This particular unit is described as an
"INSTANTANEOUS HAND WASH WATER HEATER ... that can be used with either
taps or an open outlet sprayhead". It's actually feeding a washbasin, sink
and commercial washing machine but only seems to trip when the latter is
drawing from it (so I am told: I've never been there when this happens).

Presumably there is a certain tolerance on the sensitivity of the flow
switch that tells the unit when to switch on and off, and on the
temperature at which the overheat cutout is set. At flow rates just
above the turn-off rate (which due to hysteresis(sp?) is a bit below the
turn-on rate) I've measured the water temperature at 80C, which must be
close to the overheat trip temp. Presumably under certain circumstances
the washing machine induces the heater to get up this sort of temperature
then cuts off rapidly enough for the residual heat energy in the heating
element to take the temp up enough to trip the overheat.

Apparently the more powerful 12.5kW model in this manufacturer's range
(this is a 9.5kW unit) has a thermostat operating to cut out one of the two
heating elements at high output temperatures, but this model relies on the
flow switch alone (even though it also has two elements). I suspect the
Redring unit which stipulates you use its own taps relies on these always
providing sufficient flow rate to keep the outlet temperature down. And of
course that means you could not fit a TMV to regulate the outlet
temperature as that would throttle the heater output.

So overall I think some of these units may be a poor design for practical
use.

--
John Stumbles -- http://yaph.co.uk

Extreme moderate