Main combi 30 HE losing pressure, NO LEAK!

[joiner]

Hi Plumbers

As a joiner of 38 years trade experience I do most bits of my own plumbing but do not mess with the boiler.

Last week I noticed our Main 30 HE was down to zero on the gauge but was still operating for DHW & CH.

Topped up the system to 1-1/2 barr but after about 4 hrs it was down to less than 1/2 barr.

I called out Darren my friendly plumber who installed the boiler some 4 yrs ago and after talking it through and looking around he declared that we must have a leak on the CH pipework as everything else appeared to be in order (nothing out of the external drain, bone dry).

I must agree that this was a natural assumption as we have hidden pipework and some goes under the concrete slab of our conservatory extention.

Christmas eve topping up the boiler every 3 hrs and sh1tting it that it may go down big style in minus 10 degrees tempretures with no CH or DHW over Christmas with the in-laws round for Christmas lunch.

Anyway it limped through to Boxing day with constant topping up and B&Q were open so I purchased two 15mm compresion, lever operated valves knocked a hole in the plasterboard where the pipework was routed to the suspect area and isolated the four rads.

Now refilling the system convinced that the problem had been isolated and new surface pipework would bypass the leak my relief was short lived as at first the pressure rose (expansion) but when settled it just dropped steadily.

Oh well up in the loft I went looking for any signs of a leak to no avail, everything was in good order, dry hot and me covered in fibreglass coughing my guts up (not to mention those damned building trade knees that are Donald Ducked).

Now Darren is off duty until the new year and we are still losing pressure at about 1 barr every 3 hrs and I am constantley re-filling the system.

Now even at a guess it must be having a gallon of water a day put into the system with no sign of where that may be going.

It does not drop more when the HW is run or when the cold water is run, nothing is frozen or leaking.

I have just read the installation info again and wonder if this could be backflow through a faulty valve (hard water area) or a diaphram in the diverter valve assembly or something which you may have come accross in your everday work.

Anyway all ideas are welcome and we will limp along to the new year and leave Darren in peace as he has earned his time off as he works very hard.

Thanks' Alby

 

[Billy Bob Bob]

disconnect the condensate pipe,leave the boiler off for a few hours if water still running out the recuperater has failed,not unknown on this boiler but a cheap easy fix, recuperater failure is normally caused by corrosion in the system or the use of sentinel x800 feroquest as a de scaler

 

[manx12]

definately the recuperater (or secondary heat exchange) about £130 for the part.. drain the CH circuit, the only hassle is trying to remove the heat exchange from the bottom of flue... slightly restrictive, worst case you will have to remove the flue bend which will allow you to remove the heat exchange..

 

[joiner]

Thanks' for the advice fella's, I will relay this to Darren and let you know if it is thiscommponent that has failed. Alby

 

[Billy Bob Bob]

definately the recuperater (or secondary heat exchange) about £130 for the part.. drain the CH circuit, the only hassle is trying to remove the heat exchange from the bottom of flue... slightly restrictive, worst case you will have to remove the flue bend which will allow you to remove the heat exchange..

part is around £58+ if you just buy the front cover after all thats all that fails the housing will be fine

 

[PlumbBobBob]

hi alby welcome to the forums

 

[joiner]

Thanks' steveb.

Does anyone have the part no. or know where it is available from? Alby

 

[Billy Bob Bob]

FRONT COVER ASSEMBLY 5112390 easy to replace can do them in 20 mins,try pts

 

[Puddle]

FRONT COVER ASSEMBLY 5112390 easy to replace can do them in 20 mins,try pts

Do mine in 17 mins,27 secs ................... light weight

or a you saying you can do 5112,390 in 20 mins,if so that bets me

 

[Billy Bob Bob]

Lol,now that would be fast

 

[joiner]

Thanks again gents, Darren is too busy get to us anytime soon so I have just ordered the part from uk plumbing online (£74-41 inc vat & del), I will let you know how I get on with it. Alby

 

[joiner]

Although I wanted Darren to fit the part he is still playing catch-up with his workload from the bad weather so I went ahead and did it myself.

After spannering race motorbikes and building engines in the past it was very straightforward to fit, the biggest job was dismantling the fitted cupboards and electrics at the right hand side to access the return pipe and clips.

The actual job took me about 1hr including drain-down but filling, bleeding and chasing the air around took another hour or so, with the cupboards about 1/2 days work last Saturday.

The pressure had dropped by Sunday morning from 1.25 barr to 1.1 barr which I put down to system settlement as when I did re-fill the system the pump was making a lot of bubbling noises for about 20 mins.

On Sunday I drained the hallway radiator and added the inhibitor, re-filled and bled the radiator and filled the boiler to 1.25 barr from cold.

After firing up the boiler to heat the whole house to 22 degrees for the rest of Sunday the pressure rose to 2.1 barr and at this time (Tuesday 7pm) it has dipped and rose between 1.25 barr and 2.1 barr depending on the demand put on by the heating.

When the hot water is turned on though the pressure will jump to about 2.3 barr and then settle back again afterwards.

Does all of this sound normal to you guys?

To all intents and purposes this seems to have solved the problem and a big 'Thank You' goes out to 'gas man' and 'manx12'.

Although I am a Joiner by trade I have managed to get off the tools and I am currently the Installations Manager at a medium sized double glazing company dealing with all of the subbies.

If I can return the favour by providing any advice or information please ask.

Thanks' again Alby

 

[Billy Bob Bob]

if you set it on 1 bar max when cold should rise to 2 bar hot,check your prv pipe is not running bear in mind it must be on 1 bar cold ideally as higher than this can damage the new recuperater and o rings