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Limit Thermostats

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  • closhuall
    Greetings! I purchased an ES-1A about 9 months ago and have been enjoying it ever since. I signed up to this group discussion and had been just lurking so
    Message 1 of 15 , Mar 25 10:31 AM
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      Greetings!  I purchased an ES-1A about 9 months ago and have been enjoying it ever since.  I signed up to this group discussion and had been just lurking so far,but had an issue come up today so thought I would post here.  
      I turned the machine on this morning and it was heating up, but then when I went to use it, there was no steam/water pressure.  Took off the side panels and noticed the high limit thermostats both have had some melting of the plastic clip insulators.  Not sure if it was recent or not, as I have not had the machine that long.  I pressed the reset buttons and now the machine works again, heats fine, and pressure galore.

      So, one question is there anything specifically i should be looking for that would cause the electrical leads to the thermostats to get so hot that the clip insulator would melt? (ps, the wire insulation looks fine, no damage).

      Thinking I should replace those thermostats.  Since they had gotten so hot to melt the insulator before they tripped, might be worn out and need replacement.  Any recommendations on where and what parts to replace them with?  I have searched the discussion group, but didnt find this specific answer.
      Thanks in advance! 
      Mike



    • closhuall
      A followup to the situation. I ordered a couple thermostats that I think will work and should arrive next week. In the mean time, after resetting the
      Message 2 of 15 , Mar 28 9:44 AM
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        A followup to the situation.

        I ordered a couple thermostats that I think will work and should arrive next week.  In the mean time, after resetting the thermostats, things were working ok, then this morning, had the problem again.

        I turned on the matchine to let it heat.  Came back about an hour later, and no steam pressure.  Removed the side panel and found that the wires around the thermostat were melted.  The jumper wire between the two thermostats had highly melted insulation and the plastic insulators over the blade connecters were melted and burned.  The wire that goes from one of the thermostats to the pressure switch had melted insulation.  The other wise, which i roughly tracked back to the switch seemed ok.

        I removed the wires from the thermostats.  I then bypassed the thermostats completely, connecting the wire from the switch to the wire from the pressure stat.  I wrapped in black electrical tape.  I then turned the machine on and as the boiler was heating up, the black electrical tape began to melt.  I switched the machine back off.

        The melting/heat was not from the boiler but electrical current flowing through that wire.  I disconnected and reconnected the two wires again, covered in electrical tape, and turned machine back on.  This time, as the boiler heated up, no melting of the tape.

        So, wondering if a bad switch might be causing the issue?  Would that make any sense and have any others experienced this problem?
      • Paul Albert Acosta
        You are drawing too much current through the wiring. STOP! Replace and re-land all wiring and connection points. Check the element wire connection points.
        Message 3 of 15 , Mar 28 11:05 AM
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          You are drawing too much current through the wiring.  STOP!  Replace and re-land all wiring and connection points.  Check the element wire connection points.  Now your switch maybe bad because of your actions.  Check resistance between wiring points to find the resistance problem which maybe in the THERMAL LIMIT SWITCHES that your wiring is contented to in series leading to the PSTAT and onto the HEATING ELEMENT. Your element maybe bad or water maybe leaking around it causing a SHORT.  Your MACHINE IS DESIGNED TO SHUT DOWN when too much POWER is drawn. NOW it is mandatory that you replace the damaged wiring in your unit.

          Regards,
          Paul Albert Acosta




          To: BUG-is-Bunn@yahoogroups.com
          From: michael-ashley@...
          Date: Fri, 28 Mar 2014 09:44:02 -0700
          Subject: [BUG] Re: Limit Thermostats

           
          A followup to the situation.

          I ordered a couple thermostats that I think will work and should arrive next week.  In the mean time, after resetting the thermostats, things were working ok, then this morning, had the problem again.

          I turned on the matchine to let it heat.  Came back about an hour later, and no steam pressure.  Removed the side panel and found that the wires around the thermostat were melted.  The jumper wire between the two thermostats had highly melted insulation and the plastic insulators over the blade connecters were melted and burned.  The wire that goes from one of the thermostats to the pressure switch had melted insulation.  The other wise, which i roughly tracked back to the switch seemed ok.

          I removed the wires from the thermostats.  I then bypassed the thermostats completely, connecting the wire from the switch to the wire from the pressure stat.  I wrapped in black electrical tape.  I then turned the machine on and as the boiler was heating up, the black electrical tape began to melt.  I switched the machine back off.

          The melting/heat was not from the boiler but electrical current flowing through that wire.  I disconnected and reconnected the two wires again, covered in electrical tape, and turned machine back on.  This time, as the boiler heated up, no melting of the tape.

          So, wondering if a bad switch might be causing the issue?  Would that make any sense and have any others experienced this problem?

        • closhuall
          Hi Paul, First, thank you for the useful information in your reply. I will followup on the things you mention. Second, the all caps text is unnecessary. I am
          Message 4 of 15 , Mar 28 3:46 PM
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            Hi Paul,
            First, thank you for the useful information in your reply.  I will followup on the things you mention.
            Second, the all caps text is unnecessary. I am not deaf.

            Thanks
            Mike
          • Robert Vandervoort
            Sometimes it isng even those that are the problem. If you have resistance elsewhere the weakest links can fry. I woul take the cover off the top of the
            Message 5 of 15 , Mar 29 8:22 AM
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              Sometimes it isng even those that are the problem. If you have resistance elsewhere the weakest links can fry. I woul take the cover off the top of the pressure stat, that box in the rear right corner, and move the wires over to another set of terminals. This will also put less load on your electrical circuit if the current set of terminals are lookkng kind of fried. If memory serves me, there are two more sets of terminals and it matters not which set you use, just move them over a position.

              Robert

              On Mar 25, 2014 12:31 PM, <michael-ashley@...> wrote:
               

              Greetings!  I purchased an ES-1A about 9 months ago and have been enjoying it ever since.  I signed up to this group discussion and had been just lurking so far,but had an issue come up today so thought I would post here.  

              I turned the machine on this morning and it was heating up, but then when I went to use it, there was no steam/water pressure.  Took off the side panels and noticed the high limit thermostats both have had some melting of the plastic clip insulators.  Not sure if it was recent or not, as I have not had the machine that long.  I pressed the reset buttons and now the machine works again, heats fine, and pressure galore.

              So, one question is there anything specifically i should be looking for that would cause the electrical leads to the thermostats to get so hot that the clip insulator would melt? (ps, the wire insulation looks fine, no damage).

              Thinking I should replace those thermostats.  Since they had gotten so hot to melt the insulator before they tripped, might be worn out and need replacement.  Any recommendations on where and what parts to replace them with?  I have searched the discussion group, but didnt find this specific answer.
              Thanks in advance! 
              Mike



            • edward09603
              I ve had to move to my extra sets of terminals twice now and I don t have any more ones to move too. I ve owned my machine since 1996 and I really need to look
              Message 6 of 15 , Mar 29 8:11 PM
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                I've had to move to my extra sets of terminals twice now and I don't have any more ones to move too. I've owned my machine since 1996 and I really need to look at buying a new set of switches to change this one out.  Probably should change my gauges too.


                Machine has been a beast all these years and I need to make sure it stays alive and giving life in the form of caffeine.

              • jack_burien
                Rather than replace the p-stat, why not consider replacing it with a pid. There are diagrams and info available with this group and if patient, you can find a
                Message 7 of 15 , Mar 30 7:00 AM
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                  Rather than replace the p-stat, why not consider replacing it with a pid.  There are diagrams and info available with this group and if patient, you can find a cal controller reasonably priced on ebay.  The other components are relatively inexpensive and installation is not difficult. 
                  I've done both my machines and like the better boiler control.  jack in fl  :-)
                • Bob White
                  I definitely agree with going to PID. You get better control, no moving parts and no p-stat noise. The PID negates the need for gauges which are notoriously
                  Message 8 of 15 , Mar 30 7:26 AM
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                    I definitely agree with going to PID.  You get better control, no moving parts and no p-stat noise.  The PID negates the need for gauges which are notoriously inaccurate and failure prone.

                    On Mar 30, 2014, at 10:00 AM, jack_burien@... wrote:

                    Rather than replace the p-stat, why not consider replacing it with a pid.  There are diagrams and info available with this group and if patient, you can find a cal controller reasonably priced on ebay.  The other components are relatively inexpensive and installation is not difficult.  
                    I've done both my machines and like the better boiler control.  jack in fl  :-)


                  • jack_burien
                    If you are still interested in the p-stat route, I have one I will give you for the price of freight. It s sitting in my garage and the points aren t in bad
                    Message 9 of 15 , Mar 31 7:23 AM
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                      If you are still interested in the p-stat route, I have one I will give you for the price of freight.  It's sitting in my garage and the points aren't in bad shape.  Just let me know and I can send it straight away.  I'd be glad to clean the garage.  jack in fl
                    • closhuall
                      Thanks for everyone s help. The machine is up and running and appears to be working fine. I took the opportunity to remove and check the heating element and
                      Message 10 of 15 , Apr 4, 2014
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                        Thanks for everyone's help.  The machine is up and running and appears to be working fine.
                        I took the opportunity to remove and check the heating element and it appears in good condition. I also checked resistance and based on info I found in the group postings, appears to be in line.
                        heater element - 7.8 Ohms
                        across the plug with switch on - 7.8 Ohms
                        switch on, no heater - 388 Ohms.
                        Replaced the switch to make sure it was not failing, plus it was pretty spongy anyway.  Now it is nice and crisp.
                        Replaced the high-limit thermostats and all wire from switch to element/thermostats/pstat.  Not that the wire was bad, but used the opportunity to ensure it was a non-issue.  Traced all other wires for any signs of failure, tested continuity, etc.  Moved to "virgin" contact points on the pstat as the ones being used were pretty scored.

                        There are a couple more wires on the switch that I want to replace, just cuz and while I am at it, that are female connectors with piggyback, but will need to purchase some of those connectors before I can do that.

                        The PID concept sounds intriguing, so will do some reading up on previous posts to see whats all involved there.  Sounds like it would be a fun addition to the machine.

                        Thanks again for this input and all the other helpful info from previous posts.

                        Mike


                      • Bob White
                        Good report Mike. Nice to have it back up and running.
                        Message 11 of 15 , Apr 4, 2014
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                          Good report Mike.  Nice to have it back up and running.

                          On Apr 4, 2014, at 12:44 PM, michael-ashley@... wrote:

                          Thanks for everyone's help.  The machine is up and running and appears to be working fine.

                          I took the opportunity to remove and check the heating element and it appears in good condition. I also checked resistance and based on info I found in the group postings, appears to be in line.
                          heater element - 7.8 Ohms
                          across the plug with switch on - 7.8 Ohms
                          switch on, no heater - 388 Ohms.
                          Replaced the switch to make sure it was not failing, plus it was pretty spongy anyway.  Now it is nice and crisp.
                          Replaced the high-limit thermostats and all wire from switch to element/thermostats/pstat.  Not that the wire was bad, but used the opportunity to ensure it was a non-issue.  Traced all other wires for any signs of failure, tested continuity, etc.  Moved to "virgin" contact points on the pstat as the ones being used were pretty scored.

                          There are a couple more wires on the switch that I want to replace, just cuz and while I am at it, that are female connectors with piggyback, but will need to purchase some of those connectors before I can do that.

                          The PID concept sounds intriguing, so will do some reading up on previous posts to see whats all involved there.  Sounds like it would be a fun addition to the machine.

                          Thanks again for this input and all the other helpful info from previous posts.

                          Mike




                        • sh8knj8kster
                          you wrote- ... The Sirai P-Stat used on your Bunn is more than adequate to keep the temperature you want to drink your coffee at, w/o complicating matters
                          Message 12 of 15 , Apr 5, 2014
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                            you wrote-
                            >
                            >The PID concept sounds intriguing, so will do some reading up on previous posts to see >whats all involved there.  Sounds like it would be a fun addition to the machine.
                            >


                            The Sirai P-Stat used on your Bunn is more than adequate to keep the temperature  you want to drink your coffee at, w/o complicating matters omitting it and adding PID.  Robert Harmon (Tex), one of the list owners was the first to add PID to a Bunn espresso machine, here in our group.  When he made the change from the Sirai to the PID I asked him why and his reply was "my wife doesn't care to hear the points constantly open and close on the P-Stat".  I have an idea Robert likes to fiddle with PID's as well, and I know he has a pretty good grasp on how they work, adding them to espresso machines like the Gaggia Classic I bought from Texx back in 2008 he modded using PID to control that single boiler's strike and steam temps

                            On the Gaggia Classic, going with PID made sense as the oem temp stats on that machine swung by about 40 degrees .  Our HX espresso machines operated with the Sirai P-Stat does not have that problem.  That said, be it far from me to dissuade you from changing over to PID to operate the boiler temp as there are some advantages, like having push button LED ability to change your boiler temp

                            I usually operate under the principle "if it ain't broke, don't fix it" and for me, the Sirai P-Stat has served me well the past three years running one with my Quick Mill Vetrano HX espresso machine.  However, I have to admit my Sirai P-Stat (on the vetrano) did leak like a sieve about two months ago after shutting the machine down for 3 weeks anyways while I resolved another problem the machine had (leaking inlet fuel valve)

                            When I started the Vetrano up after making the repair, that's when the P-Stat leak became known


                            And it leaked where you see the visible seal.  Stopping the leak was simple though, and only a matter of removing the part the seal seats in, cleaning the mating surface on the underneath portion where the seal seats (using 4 ought steel wool).  After buttoning it up, the leak issue was resolved.  That will never happen with a PID, but then too, when the PID goes Tango Ivex Tango's Uriah Provo, I would be totally lost for a solution


                            Best,


                            Jake
                            Reddick Fla.     
                          • closhuall
                            Interesting you mention the noise from the machine. I guess the clicking of the pstat has not bothered me much. But, the machine definitely had an audible
                            Message 13 of 15 , Apr 7, 2014
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                              Interesting you mention the noise from the machine.  I guess the clicking of the pstat has not bothered me much.  But, the machine definitely had an audible "breath", as I would hear a small amount of steam escape every 4 or 5 seconds.  Not having had the machine that long and never having owned an HX machine, I did not know if that was normal or not.  But, after searching the group and finding posts about the anti-vacuum valve, I removed it and descaled.  It has been silent ever since.
                            • closhuall
                              Thanks for your input Jake... I did decide to stay with the pstat instead of going the PID route. I did read some other sites where people are using PIDs, but
                              Message 14 of 15 , Apr 16, 2014
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                                Thanks for your input Jake...

                                I did decide to stay with the pstat instead of going the PID route.  I did read some other sites where people are using PIDs, but instead of temperature switching, they use a pressure transducer in place of the pstat.  It would certainly stop the noise of the pstat, but the transducers seemed to be a little cost prohibitive to me (and didnt want to think about a used pressure transducer).

                                I believe the pstat in the machine was original (P302-8) and probably needed a new membrane kit.  Price was about $30 for the kit.  Found a new pstat on ebay for $60 (P302-6) so got that instead.  A noticeable improvement in the deadband as it is reduced a lot with the new pstat.  So the membrane was certainly in need of replacement.  I also added an SSR to do the high amp switching, using the pstat to switch the SSR on and off.  Will see if only passing low current through the pstat helps the longevity of the contacts (it should). 

                                Take care
                                Mike

                              • sh8knj8kster
                                Thanks for your input Jake... I did decide to stay with the pstat instead of going the PID route. I did read some other sites where people are using PIDs, but
                                Message 15 of 15 , Apr 17, 2014
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                                  Thanks for your input Jake...

                                  I did decide to stay with the pstat instead of going the PID route.  I did read some other sites where people are using PIDs, but instead of temperature switching, they use a pressure transducer in place of the pstat.  It would certainly stop the noise of the pstat, but the transducers seemed to be a little cost prohibitive to me (and didnt want to think about a used pressure transducer).

                                  I believe the pstat in the machine was original (P302-8) and probably needed a new membrane kit.  Price was about $30 for the kit.  Found a new pstat on ebay for $60 (P302-6) so got that instead.  A noticeable improvement in the deadband as it is reduced a lot with the new pstat.  So the membrane was certainly in need of replacement.  I also added an SSR to do the high amp switching, using the pstat to switch the SSR on and off.  Will see if only passing low current through the pstat helps the longevity of the contacts (it should). 

                                  Take care
                                  Mike





                                  ~~~Glad to have been of some help to you Mike.  I myself have never personally been bothered by the noise made when the points of the P-Stat open and close.  In fact, I find the noise quite soothing=:-)  Music to my ears you might say, as I know the boiler is operating when I hear the points open and close



                                  Best,



                                  Jake

                                  Reddick Fla.


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