# Swap 125 degree thermostat with 145° one. Is it possible?



## mexier (Aug 21, 2014)

Hello, actual situation showed in the picture









In the meanwhile of finding a way to remove broken screw from the boiler, I was also looking for another thermostat but I can't find it.

The original one was set at 125 celsius degree manual reset and looks an old version.

I can only find an 145 and 165 degree model or also 125 but autoreset mode.

Can I put a 145 one? And in case do I need to raplace some in the electronical board? Thanks for your help


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## jpaul__ (Feb 19, 2016)

recent thread on this forum about removing bolts

can you solder a copper strip say onto boiler under which you prop the thermostat with some heat conducting paste on its face, if necessary, or if you get it out this one from bellabarista?

since it is manual reset suggests it is a safety thermostat so need to replace it with like.

Do not see why electronic might need changing


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## Mad Wally (Feb 24, 2016)

mexier said:


> Hello, actual situation showed in the picture
> 
> 
> 
> ...


NEVER install a thermostat with a higher temperature unless you are an expert and know exactly what you are doing.

Manual reset means it is the safety limit thermostat, a crucial safety device. An incorrect thermostat, incorrect mounting or a wiring error may cause catastrophic failure of the boiler with very severe consequences. Use original parts only and mount and wire correctly. If you do not feel certain then have it done by a professional. See this as working on the brakes of your car.


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## mexier (Aug 21, 2014)

Thanks for your tips. I'll try to remove the screw and if I'll not be able well I really consider solder option.

About the 145 degree...not that I wan to change it but it's unavailable becasue out of production.

In this case I can put a thermostat set @ 125 without manual reset but auto. Would you go this way? Sorry but really not much expert about this...


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## Mad Wally (Feb 24, 2016)

The pavoni one is 127°C

https://www.espressoparts.com/parts/commercial-espresso-machine-parts/browse-common-espresso-machine-parts/thermostats?limit=30


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## Dylan (Dec 5, 2011)

I did the exact same thing to mine, they are delicate, they dont need much more than hand tightness.

I removed it by drilling a tiny hole into the shaft and then using a small flat head screwdriver pressing into this little hole I unscrewed it.

You will be fine with an auto reset thermostat, if you have found one that is a 125 then great.


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## Dylan (Dec 5, 2011)

I did the exact same thing to mine, they are delicate, they dont need much more than hand tightness.

I removed it by drilling a tiny hole into the shaft and then using a small flat head screwdriver pressing into this little hole I unscrewed it.

You will be fine with an auto reset thermostat, if you have found one that is a 125 then great.

Your machine should also have one of these:










Which is another safety device which blows if the pressure gets too high. I appreciate mad wally's cautiousness here but the machinery here isn't complex.


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## mexier (Aug 21, 2014)

Yes the check valve is the 2nd overpressure mechanism of protection. An essential part of course.

Thanks for your imput, 125° will be my choice (althoug I wonder why so many different temperature set for boiler with same electrical resistance and liter capacity)

Dylan did u use the dremel for making the tiny hole or maybe a drill press?

I'm also a bit scared about the width of the boiler. The nut is into it for no more than 4 mm (at max) so I don't wanna transfix it.


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## Dylan (Dec 5, 2011)

Temperature directly relates to the pressure in the boiler, so higher temp is higher pressure. In a machine intended for your average home there is no need for you boiler to be much over 1bar so they temp for the thermostat trip can be much lower, less pressure on the internals of the machine I would assume is a good thing. Why some use 125 and some 120 and others 127 etc etc etc is a mystery to me however.

Yea, I used a dremel with a drill bit intended for drilling holes in circuit boards, I think i broke a few of them too. It may be a pretty bad idea however if you don't get it centre and muck up the threads.

Do just try getting a very small flat head screwdriver (like a jewelry screwdriver) and see if you can get purchase on what is left there, as its brass you might even be able to wedge the screwdriver into the metal a little.


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## Dylan (Dec 5, 2011)

I was just thinking about this, and I could be missing a part of the puzzle that means the following is untrue, but...

If you go to this link you can put in saturated steam pressure: http://www.tlv.com/global/TI/calculator/steam-table-temperature.html

At 145c the machine pressure is 3.1bar

This seems inordinately high, even for a machine that might be used commercially... why have a trip that doesn't trip until such a high temp/pressure?

I mean the safety valve blows long before the machine ever reaches 3 bar, but you could have a 135 (2.1bar) thermostat and still have plenty of overhead if you wanted to keep the machine at a silly high pressure.

It is perhaps unimportant to muse on this, but it does seem odd to me.


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## mexier (Aug 21, 2014)

Thanks for the link, very useful.

Well just to try to understand, safety valve of my machine (LSM 100,commercial, 1 group) in certified to open @ 1.8 bar. According to TLV steam pressure calculator it matches @ 131,5 celcius degree. So around this thermostat value I can find a sense...above sincerely not i.e. 145 or also 165 °C

Maybe something escapes to me...


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## jpaul__ (Feb 19, 2016)

my thoughts ..

there is the steam thermostat itself, in addition to this manually resettable safety thermostat, but it seems logical this safety thermostat should correspond to a temperature higher than the temperature corresponding to vapour pressure where safety valve would fire(since that is automatically resettable.)

Also this manually resettable thermostat will deal with situation where there is no water left - so no steam .

Heating element too has a cut-off fuse as well (resettable ?)

Also although safety valve is a standardised/qualified product I do not know whether you should test them after machine is many years old ( by disconnecting steam thermostat ?) or other maintenance , maybe just replacing ?


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## Mad Wally (Feb 24, 2016)

jpaul__ said:


> my thoughts ..
> 
> there is the steam thermostat itself, in addition to this manually resettable safety thermostat, but it seems logical this safety thermostat should correspond to a temperature higher than the temperature corresponding to vapour pressure where safety valve would fire(since that is automatically resettable.)
> 
> ...


As a senior process and safety engineer for hydrogen production plants (by means of steam reforming) I have designed and reviewed many safety systems for steam generators and thermal reactors. What they all have in common is the order in which they intervene. First a control sensor or thermostat then a non adjustable manual reset safety limit thermostat and finally a safety valve. The safety valve is really a last resort and should never open under normal circumstances.


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## Dylan (Dec 5, 2011)

My safety valve blows before the thermostat trip.


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## DavecUK (Aug 6, 2013)

Mad Wally said:


> As a senior process and safety engineer for hydrogen production plants (by means of steam reforming) I have designed and reviewed many safety systems for steam generators and thermal reactors. What they all have in common is the order in which they intervene. First a control sensor or thermostat then a non adjustable manual reset safety limit thermostat and finally a safety valve. The safety valve is really a last resort and should never open under normal circumstances.


First absolutely correct reply I have seen......unfortunately not all espresso machines are designed like this.

You have a few options, find a 125 manual reset, or use a 127 manual reset that someone has identified to you....The reason the above poster is absolutely correct is because of the way the levels of protection should work and what each ones job is:

1. Pressurestat = process control

2. Manual Limit stat (in case pressure stat fails to operate correctly) = make system safe by cutting power and NOT restoring it without manual intervention, thus protecting your investment.

3. Pressure release valve to prevent boiler rupture/explosion. = stop things going bang if 1 and 2 fail....don't care too much about your investment.

If 3 happens for any real length of time, there won't be any water to easily operate the limit stat, apart from free air radiation from your "glowing" heating element, hence they are really designed to operate which the boiler still has water/steam in it. Plus your "electrical" machine is full of water condensate. Hence the order of operation.

You could probably get away with using one of these, especially if you change your limit stat for one that operates at 2-2.3 bar...which should be absolutely fine for your boiler.

http://sinolec.co.uk/en/manual-reset-thermostat/1211227-thermal-cut-out-130c-nc.html


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## mexier (Aug 21, 2014)

Thanks for all the answers that helped me to clarify mechanisms I wasn't aware of before. So if I understood well It's preferable to find a thermostat with MANUAL reset and possibily at 125-127 °C or at 130 but changing pressurstat (normally working between 0.5-1.4) and buying one with higher limit, right?

I'd prefer keeping my pstat since it's brand new, so 125-127 °C safety thermostat would be the first choice (even if at 127° pressure inside boiler is 1,45 bar).

Correct me if I misunderstood some and I'm wrong, please.


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## Mad Wally (Feb 24, 2016)

Dylan said:


> I was just thinking about this, and I could be missing a part of the puzzle that means the following is untrue, but...
> 
> If you go to this link you can put in saturated steam pressure: http://www.tlv.com/global/TI/calculator/steam-table-temperature.html
> 
> ...


No your assumptions are spot on. Have an adjustable controlling pressostat that keeps the boiler pressure typically between 0.8 and 1.2 bar. Then a non adjustable safety limit thermostat in the 125 to 130°C region limiting the pressure to around 1.4 to 1.7 bar and finally a non adjustable safety valve set at around 2.5 to 3.0 bar. The controlling pressostat is user adjustable. The safety thermostat and safety valve settings are selected by the manufacturer so the boiler (pressure vessel) will never exceed its design pressure.


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## jpaul__ (Feb 19, 2016)

DavecUK, following you comment about not all machines are designed like this, and MadWally's clear description.

I looked at the internals of the Bezzera BZ02 HX machine I recently acquired and was surprised to see it only seems

to have two safety mechanism on the boiler:

- safety valve 2.5bar

- pressostat 1.2bar (probably adjustable)

[also a thermic cut out 130c near element]

whereas on my previous (sold) Rancilio Silvia/Audrey single boiler

- thermostat 110 brew

- thermostat 140 steam

- thermostat 165 resettable

- pressostat ( not sure of pressure )

No safety valve

so it seems with Bezerra there is no resettable thermostat if pressostat fails, safety valve is only recourse (I had expected to see a thermostat hiding somewhere but parts diagram and looking do not reveal it)

Equally on the Rancilio just looking at exploded parts diagram, the absence of a safety valve seems surprising (maybe newer versions have one)

so are both these machines deficient with respect to safety mechanisms ?


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## DavecUK (Aug 6, 2013)

jpaul__ said:


> DavecUK, following you comment about not all machines are designed like this, and MadWally's clear description..........
> 
> so it seems with Bezerra there is no resettable thermostat if pressostat fails, safety valve is only recourse (I had expected to see a thermostat hiding somewhere but parts diagram and looking do not reveal it)
> 
> ...


The thermal saftey breaker, limit stat fusible link etc.. should ideally be a non reset thermal breaker, which for the Bezerra it sounds like it is. Being manually resettable is not really a safety requirement IMO and being self resetting is not a good thing. *The Bezzera seems to follow all good safety protocols.*

With the Racilio, you concern is caused by not understanding the issues around a single boiler non HX machine vs an HX machine. The rancilio boiler is capable of withstanding pressures well in excess of 15 bar, the expansion valve will vent at 15 bar or below, so the various thermostats are fine for that machine. It doesn't have a pressurestat, it simply uses the 110C and 140 C thermostats for brew and then steam respectively, depending on which one you switch in. Bear in mind the very best of these thermostats have an off or on accuracy of 3C (I am pretty certain they won't have fitted the best) and usually they are +/- 7C. The dead band between on and off can be even larger at up to 10C.....so horrendously inaccurate. They are very basic machines made to a price....BUT, not unsafe.



> whereas on my previous (sold) Rancilio Silvia/Audrey single boiler
> 
> - thermostat 110 brew
> 
> ...


The 165C thermostat is resettable and will cut power at around 6 or 7 bar...well within the boilers design limits. If this "limit stat" fails, then the expansion valve will vent at 15 bar, again still well within the boilers design pressure, which is probably in excess of 25 bar. *So the Rancilio Sylvia is NOT unsafe and follows all good design principles for safety.*


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## DreamerB (May 22, 2016)

Although I do not advise doing it, I do not suggest you do it, I do not recommend you do as I did and I most certainly am advising you to not do it. I ran my isomac for a few months without a thermal break.

It was "unsafe" to do so, it could have blown up or worse produced bad shots. It didn't though.

It happened because I couldn't find a thermal fuse that was at the right temp and I thought f*** it you only live once. I gave it a shot. It was stable and the power draw was right on and stayed that way. I figured the age of the fuse caused a fault to show up because I never found a reason for it to originally blow, machine is gone now to a new home with the right fuse.

My advice is don't do what I did... For any reason what so ever. Use the right part for the job or don't use the machine at all.


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## jpaul__ (Feb 19, 2016)

Thanks,

yes looking again at rancilio parts diagram, as you say no pressostat ( I was confused by the water level pressure switch was labelled pressostat







)

when you said expansion valve, i infer that is aka the opv valve (but maybe called former due to difference between hx / single boiler)

I had not contemplated before that the silivia boiler is taking the full brew pressure from the pump, whereas for the hx it is just the 1.2 bar steam pressure, although the build quality/strength of the boilers does not appear so different.


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## DavecUK (Aug 6, 2013)

jpaul__ said:


> I had not contemplated before that the silivia boiler is taking the full brew pressure from the pump, whereas for the hx it is just the 1.2 bar steam pressure, although the build quality/strength of the boilers does not appear so different.


The steam boiler is often a little thinner and usually doesn't have rounded corners, just a flat flange each end. Even so, as you have rightly thought, the steam boilers can take much more pressure than whatever the safety valve is set to. Any standard steam boiler can probably take 8 bar plus. The photo of the stem boiler of the commercial machine and all the damage it did, shows the pressure would have been much higher than 2 bar.


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## mexier (Aug 21, 2014)

Very useful discussion !







:beer:


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## mexier (Aug 21, 2014)

Quick update









Now waiting for the new pavoni thermostat


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