On 26/11/21 9:00 am, billherbst wrote:
Kevin, what you wrote makes perfect sense to me. I'll bet you're right
that the pressure switch is no longer sensing boiler pressure because
of scale blockage in the copper pipe. The city water in Columbia is
ridiculously hard — 255 ppm, according to my cheap little tester.
Scale was the cause of the problem I had a year ago with the boiler
refill valve sticking. That's why I asked whether scale could cause
the problem in my original post. I'll remove the copper pipe that
connects the pressure switch to the boiler and give it a citric acid
bath.
Sometime ago I downloaded the "Brewtus Compendium" - a PDF file
outlining how a PID controller is added etc etc - by C.S. Lennon. Very
useful document. It doesn't actually reflect the standard wiring on
mine (mine has an SSR controlling the brew boiler, and the diagram does
not show that...); but it is really handy for diagnosis flow chart time!
The wiring shows the heating elements fed mains and going through the
steam boiler pstat. The other lead on the pstat is the N/O lead and it
then goes to the brew boiler. So if the steam boiler keeps chugging
away it can only be the pstat..
The document is available on the brewtus group pages somewhere. I
commend it to everyone!
Apropos water :) Here, at my house, I use only rainwater. I have a
choice of rainwater or water from my dam and I'm not drinking that! The
rainwater is perfectly 'soft' and scale is simply not an issue for me.
But I regularly de-scale friend and family machines. Citric is your
friend in that endeavour, but one place you might find it tough to get
to is the bottom of the U. For a couple of $$'s you can get a bicycle
brake cable inner. Get a stainless one, carefully 'fluff' the end a
tiny, tiny bit and you have a robust 1.5m or so long device you can push
through pipes to clean them. Fill with citric first, of course, and
then chimney sweep style clean the sucker! That has not let me down
yet, and it even works with thermoblock machines!
Cheers
/Kevin
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