Re: Bad P-stat?




"Mike" <nospam@xxxxxxxxxxxxx> wrote in message
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"Jack Denver" <nunuvyer@xxxxxxxxxxxx> wrote in message
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"Mike" <nospam@xxxxxxxxxxxxx> wrote in message
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It's a BZ99. The machine is several years old, so it's probably well
overdue for a new p-stat anyway.

I've considered doing the PID thing, but as far as the temp probe goes,
I don't think there's any free ports on the boiler available unless
there's one underneath.


The obvious free port is the one currently occupied by the pstat.

Certainly I could do it that way, but I would prefer to leave the pstat in
place and set to a higher setting as an extra margin of safety.

However, assuming I would want to go the route you're suggesting, does
anyone sell a suitable kit for my machine?

I'm not sure I understand your thinking - your pstat doesn't have a pstat
backup and the machine is still "safe" right now. Any PID will be more
reliable than the pstat that it replaces 'cause the PID is solid state and
the pstat has moving parts and are known to be unreliable - yours already
has proven its unreliability.

My Oscar has a safety overtemp thermostat (in addition to the steam safety
valve and the reservoir empty sensor). If the BZ has one of those (like a
click thermostat on a single boiler but once they hit the set temp you have
to push a reset button to get the machine back on) then there's really no
need for a 3rd line of defense. If you leave a pstat in place and set high,
it will never get any exercise and probably won't work when you need it
anyway.

As for a kit, I dunno. I got an Auber Instruments Chinese PID and an SSR
off their website. I think they also sell on ebay I got a project box, wire
and various spade connectors at Radio Shack. For the probe, an altie was
kind enough to custom make one for me (using the body of vaccum breaker
valve with the correct thread as a starting point) but I recall that Omega
will also make up probes to your spec. Putting the whole thing together was
maybe less than an hour - probe wires to the thermocouple terminals on the
PID, SSR output takes the place of the terminals of the pstat, steal power
off with a double spade on the machine's power switch, control wire from the
PID to the SSR input, done.


.

Relevant Pages

  • Re: Bad P-stat?
    ... I've considered doing the PID thing, but as far as the temp probe goes, I don't think there's any free ports on the boiler available unless there's one underneath. ... Certainly I could do it that way, but I would prefer to leave the pstat in place and set to a higher setting as an extra margin of safety. ... The PID setup introduces an extra point of failure because you now have the SSR and the PID itself to worry about. ...
    (alt.coffee)
  • Re: Bad P-stat?
    ... I've considered doing the PID thing, but as far as the temp probe goes, I don't think there's any free ports on the boiler available unless there's one underneath. ... Certainly I could do it that way, but I would prefer to leave the pstat in place and set to a higher setting as an extra margin of safety. ... The PID setup introduces an extra point of failure because you now have the SSR and the PID itself to worry about. ...
    (alt.coffee)
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    ... Thermostats/pressurestats are well proven and they see no reason to fix what ... PID controllers such as the Fuji ... a small home pstat based machines. ... click thermostats on single boiler machines. ...
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  • Re: Should I PID my Heat Exchanger?
    ... So one really could replace a pressurestat ... with a PID as long as some safety measures are in place. ... >> Silvia or similar single boiler machine. ... The pstat is set to cycle at very high boiler ...
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  • Re: How to install a PID for my Bunn ES-1A?
    ... I'd run the power to the PID thru an inline fuse holder (glass automotive ... Run the 2 wires that formerly went to your pstat to the SSR output contacts. ... No harm in keeping the pressure gauges - worst case if you lack a pump gauge ...
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