Pressure build up in Sime Super 90 mkII combi boiler

BotchItMyself · 9 Sep 2005

Before I go into my problem, just want to say, what a good community this is. Now as I've buttered you up, could somebody please help me with my problem.

I found water spurting out of a small hosepipe hanging out of the bottom of my boiler. Presumably this is from the pressure release valve? I checked the water pressure and saw that it was about 3 bar, so released the manual pressure release valve and dropped it to 1 bar. Unfortunately, the next day it was back to 3 bar and spirting water again. I giggled my way through this forum (some of you really are mad'eads

) and have consequently done the following things;

1 - completely emptied the system, refilled it making sure no airlocks
2 - checked the expansion vessel - there is pressure and no water in it
3 - removed the filling loop type thing between the DHW and the CH - the braided pipe

None of this has fixed the problem. I'm now really stuck so was wondering if anyone has any other ideas before I make a call a plumber.

PS - I know someone will probably tell me that the boiler's a pile of bob (I don't need to be told this) but as we've got new princess in the house, can't afford a new one at the moment - and probably won't for decades come to think of it!!

Slugbabydotcom · 10 Sep 2005

Giggle your way down to the DHW [plate] heat exchanger and then jiggle some money out of your pockets for a new one

BotchItMyself · 10 Sep 2005

Thanks for the reply Slugbaby. Suddenly I'm not giggling anymore.

Is there any way that this can be tested before I order one and is it difficult to change?

kevplumb · 10 Sep 2005

Is there any way that this can be tested

isolate the cold water at the boiler and see if the pressure stops rising

Agile · 10 Sep 2005

This is a pretty unusual fault and I only encounter typically one every year amongst about 3000 boilers.

If the pressure stops rising when the CW into the boiler is disconnected then there is another reverse test you can to.

Pressurise the boiler to two Bar and disconnect the cold feed and hot water out connections, if its the plate HE leaking then water will continue to drip out of the hot and cold connections on the boiler.

Tony Glazier

Slugbabydotcom · 10 Sep 2005

Good news is that they are not that expensive for a boiler part... click this and use the word 'exchanger' for your search.

BotchItMyself · 10 Sep 2005

Agile said:
This is a pretty unusual fault and I only encounter typically one every year amongst about 3000 boilers.

Well that sounds about right! I hear what you say about it being a rare fault, but I cannot think or find in the forums anything else it could be.

slugbabydotcom said:
Good news is that they are not that expensive for a boiler part

Brilliant, thank you for letting me know that one Slugbaby.

Thanks fellas for your replies and suggestions, they really are appreciated. Long live your generosity in sharing your knowledge and experience with others

Agile · 10 Sep 2005

Although its a pretty unusual fault its one which is quite easily identified and already I am pretty sure thats your problem.

Its better to do several tests to confirm its that before replacing parts though.

In the real world we encounter some extreme examples of stupid and unexpected things.

Once I diagnosed that there was a cold water connection into the hot water outlet from the boiler. This prevented the combi sensing any hot water demand. It was easy to diagnose but the landlord said there had been no plumbing changes made.

He was reluctant to let me look as I think he did not believe my diagnosis! I soon found it though! There was a bath mixer tap on which he had capped off the shower point and forcibly screwed the separate shower valves shut to stop the tenant using the shower and spilling water on the floor.

The tenant had turned the shower valves back on to use the shower but replaced the final cap after showering but left the valves turned on thus bypassing cold into hot.

This was a most unusual bath mixer tap! It had two taps for filling the bath and ANOTHER two valves for supplying the shower! First and last I have ever seen like this.

Tony Glazier

BotchItMyself · 10 Sep 2005

Makes my attempts at plumbing seem positively professional!!!

I used to be a working jeweller. Remembering how some items of jewellery were "repaired" still makes me somewhat flabbergasted. A large diamond - worth about £600 - superglued into a setting, chains "mended" with fuse wire or a bent paperclip. It doesn't surprise me that plumbers have similar unbelievable stories about what some bodgers have done. Still, you should be grateful - it keeps you all in work

Carl

PS thanks for the confirmation

Alejandro · 30 Mar 2009

I have inadvertantly (turning mains water back on whilst feed water tap to boiler system is open) sent my boiler pressure upto 3 bar. I see mention of a manual release valve in the post above, but no idea what it is or looks like... please...

Is it safe to use the boiler as it is
Do I need to somehow (how?!) reduce the pressure back down to just above 1 bar where it was?

All this caused by trying to fix a tiny weep on incoming main stoptap! Arghhh! Any advice or help please, thanks folks

Agile · 31 Mar 2009

Bleed about 2 li from a rad bleed screw to reduce the pressure to 1.5 Bar and do it immediately before you spoil the boiler.

Try tightening the gland nut on the stopcock ( the one around the shaft ).

Tony Glazier

Alejandro · 31 Mar 2009

Thanks for the response, much appreciated- I have it sorted now.

aniel · 24 Apr 2009

Hi,

Young and inexperienced owner here so please be gentle

I had a build up of pressure to about 3 bars, followed the advice and used the Red Release valve called 'Safety Valve' in the manual. Straight away the pressure dropped and went back into blue for a while.

But now the pressure is dropping very slowly and hasnt steadied. Pressure drops below 1 and i have to manually re-pressurise using the blue screws for cold water and C.H.

Checked outside and the discharge pipe is dripping water ao it must be constantly releasing but i cant figure out how to stop it!

Please could someone guide me how to steady the pressure and stop the leak?

hobhead · 26 Sep 2009

The pressure relief valve will often leak after opening, due to debris on the valve seat. You could try operating it again and it may seat if you're lucky..otherwise would need replacing.

diynot

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Pressure build up in Sime Super 90 mkII combi boiler

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