Potterton Lynx II boiler discharg CH water through waste pip

[Slay]

Well that should say:
'Potterton Lynx II boiler discharging CH water through waste pipe'

I had a problem when I came back from a business trip, and found the 'low pressure' light on and boiler inoperative. The CH pressure guage did show low pressure (a v slow leak somewhere over the years, never found it, but it seems to have been OK until now. Topping it up from the mains U-pipe and resetting for 5 seconds didnt work). I used the instruction guide's flowchart to identify the Pressure switch was faulty. Sure enough, disconnecting one of the leads seemed to do the trick, and I ordered a new pressure switch to install.

Which I did at the weekend. I drained the system as per instructions by releasing the pressure via the Pressure Relief Valve, and draining via the CH drain-off screw. Replaced the pressure switch with no problems, but ran into 2 problems:

1) The CH flow and return isolation valves started weeping. Figured that they hadnt been used in so long, and thats what happens. Piece of cr*p.
2) Main problem, however, is that, when I topped up the CH circuit, it promptly started ejecting it through the waste pipe in the wall. So in a few minutes, my pressure was down to zero. Its like the Pressure Relief Valve was constantly activated or something.

Is there a way around this? I can get hot water (so at least I don't stink at work) but would like to sort this out. Is there a tweak on the PRV that needs to be done? Odd thing is, I would have thought the Low pressure light would have come on, or is that only for the main hot water?

Certainly cant replace the PRV, its way round the back of the pipes, and a man has to know his limits. I figure that I need a specialist to check the boiler over anyway, and fix the weeping valves, but any advice would be welcomed.

I am not a pro by any stretch, but I did study engineering.

cheers
Slay

 

[baxpoti]

The PRV and Isolators need replacing.

Be aware of, how much money you throw, at a very old boiler.

 

[waterworks]

By opening the pressure relief valve you have got some sludge holding the valve off it's seating, you need to turn it on and off with a snap action a few times this will usually reseat it, the repressurise.

 

[Slay]

thanks for that, i will give it a try.

Another Q: now that the water in the CH loop wil be new, do I need to get someone in to give it some 'treatment'? I guess de-oxygenate or something, just heard that this is sometimes done?

cheers
Slay

 

[mickyg]

check your wiring on your low water pressure switch, sounds like they're are wrong. the light should come on when the pressure is on 0.

 

[Slay]

hmm, thats what I thought. perhaps I have a faulty WPS. How would I check that? I suppose I could turn off the water mains and see if the light pops up, but I dont really want to blow myself up.

Also, with the pressure relief valve, tried to get rid of any sludge. But when you say 'turn it on and off' thats not how the mechanism works, it's a turn until it 'snaps' to the normal position. I can only turn it one way. I can hear the water draining out when I do that, but I guess I still get have some blockage, as the water trickles out the drainage when I refill it.

May be the time for a new boiler, especially with the weeping isolation valves - how does stuff like that get out on the market? The one time they are supposed to do their job and they fail.

cheers
Slay

 

[Slay]

thanks for the replies, by the way. good to see a forum where people with knowledge respond so quickly...cheers!