# Advice needed - Fracino Cherub overpressure issue



## nightslayer (May 29, 2016)

I have a Cherub that I believe is 7 years old - bought it secondhand off a forumite and have only used Ashbeck water with it. Have recently encountered an issue where the machine will overpressure after about an hour of being on, and set off the safety valve - it appears that the heating element does not shut off. I am presuming that the issue is with the pressurestat, and that this isn't an issue with contacts (because then it shouldn't be turning on), so it is probably either a spring (?) issue or a stuck diaphragm, which is my best working assumption. What I cannot fathom is why the pressurestat works for the first 45min or so of operation (this window has been steadily growing smaller, however.) - presumably if it's a diaphragm issue it shouldn't work at all? I also presume this isn't a scale issue given the fact that the pressurestat is located on top of (and directly screwed on to) the boiler, rather than with a pipe going through the bottom. Descaling the boiler doesn't seem to have changed anything.

Couple of questions -

1. Does anyone think that getting in a new pressurestat will solve this issue? Fracino are quoting me £78 for the part so I am very reluctant to buy one in unless it definitely is the problematic issue.

2. Is there any cheaper place to get a Sirai pressurestat - Fracino doesn't say what model exactly but I think its the 30A P302?

3. How difficult is it to remove the pressurestat and reinstall it myself? I have a couple of small spanners and adjustable spanners but nothing heavy duty.. I also have PTFE tape if necessary.

4. Would the safety valve need to be replaced, now that it's been blown a couple of times?

Apologies if this thread belongs better in the faults rather than the Fracino forum!


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## NewboyUK (Jul 14, 2018)

Are you handy with a test meter?

And have you remover to top off the pressure switch to see the condition of it?


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## nightslayer (May 29, 2016)

Not done either yet, and don't have a test meter. The issue isn't that there's no current going through though; issue is that the machine isn't cycling off when it hits 1.2bar, which is why I think it might be a diaphragm/pressure switch issue? It cycles on and off fine for about 30-45 minutes before giving me issues. Happy to run whatever diagnostics are necessary!


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## NewboyUK (Jul 14, 2018)

Pressure switch.

Potentially after 45 mins the heat is built up and contacts stick together.

Pressure stats are normally closed switches so can stick shut resulting in over pressure.


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## nightslayer (May 29, 2016)

Cheers mate. Didn't realise they can stick shut. Do you know if there's a difference between the 20A (P303) and 30A (P302) variety? Also are industrial grade tools necessary for removal? I do not, for example, have a spanner torque bar..


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## NewboyUK (Jul 14, 2018)

30a version preferred as it seems to last longer. Fracino dont use the 20a one any more for a good reason.

Just screwdrivers and a few spanners needed. Easy job - just make sure off/cold before you start.


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## nightslayer (May 29, 2016)

(Double post)


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## nightslayer (May 29, 2016)

NewboyUK said:


> 30a version preferred as it seems to last longer. Fracino dont use the 20a one any more for a good reason.
> 
> Just screwdrivers and a few spanners needed. Easy job - just make sure off/cold before you start.


 Was hoping it'd be an easy job - can't seem to get the pressurestat off! The contacts don't seem to be welded together (though there is a fair bit of carbon and some shiny bits) so I'm wondering if it's scale/a hardened diaphragm. There seem to be two nuts which are separated by a bit of pipe. I can get the top nut closest to the pressure stat to turn but that just seems to turn the whole pressurestat with it, which can't make a full rotation in the machine because of two pipes in the way. I also can't get the nut to turn independently of the pressurestat. Very annoyingly, there's hardly any room to fit a spanner in there, much less turn it! Now I'm also not sure what to do to tighten it back on?

edit: have turned it on to have a look with the lid off and it appears the pressure stat is leaking steam - the presence of some scale on the metal bit suggests it's not just due to my having loosened the pressurestat..


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## nightslayer (May 29, 2016)

Am struggling to figure out how to get this thing off - am I supposed to hold the pressurestat with one hand while pulling at the nut below clockwise looking down..? Should I remove the pressure gauge pipe (or is that nut also welded on tight) for easier access to the pressurestat nuts? There don't seem to be any videos online of people replacing these Sirais!


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## NewboyUK (Jul 14, 2018)

nightslayer said:


> Am struggling to figure out how to get this thing off - am I supposed to hold the pressurestat with one hand while pulling at the nut below clockwise looking down..? Should I remove the pressure gauge pipe (or is that nut also welded on tight) for easier access to the pressurestat nuts? There don't seem to be any videos online of people replacing these Sirais!


 Yes to all if its easier. No real right or wrong way


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## nightslayer (May 29, 2016)

Latest development - got in there, managed to get the pressurestat off by removing it from the boiler side first, disassembled the diaphragm assembly and.. clean as a whistle and still completely pliable. No scale whatsoever to speak of, and no scale in the boiler pipe leading to the pressurestat either. Have put the pressurestat assembly back on with PTFE on the threads but it's now sprung a leak - are some threads not meant to have PTFE on them?


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## NewboyUK (Jul 14, 2018)

Your not looking for scale or anything like that. It would be a failing stat where contacts have stuck together probably from heat. The springs inside may not be as bouncy as its 1st youth.

Personaly I dont use ptfe on anything.

If the pipes are flat on the end then a small copper washer will help. If it a ball shape then usually it will just seal without any extras.

Maybe easyier to attach the small pipe to the stat first then offer the whole assembly up to the boiler


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## nightslayer (May 29, 2016)

As an update - have reconnected the bits with just one round of PTFE on the threads (for easier removal in the future); there is still very intermittent hissing but it seems negligible so I have decided to live with the issue for now (or may go in and tighten things up if it still doesn't seat properly with a couple more heating and cooling cycles), and am just glad that the pressurestat is no longer overheating my boiler or the joints permanently leaking!


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