Water pressure on boiler keeps going

Albermarle

ThisIsWeird said:

Albermarle said:

Just to check something with you on some of these points for my own interest ( if I may)
My system boiler has no pressure display/readout, so I have always presumed the external pressure gauge/dial ( below the EV and near where you can top up if necessary) is doing the same job? and that presumably internally in the boiler there must be an internal pressure monitoring system, even though there is no display for one?

I have also a megaflo type tank next to the boiler, with all the usual pipe work involved.
The 15mm copper pipe that goes outside the house is actually plumbed into this pipework, and I presume is the pressure relief outlet for both the heating and the hot water tank. For sure it is not directly/physically coming out of the boiler. Is this normal as you and others often refer to the copper overflow pipe coming directly down out of the boiler ( like the condensate pipe) ?
When I have had water coming out of that pipe in the past it has been related to problems with the megaflo EV rather than the central heating one, but this does not seem to affect the central heating pressure.
So it would seem in some cases, like mine, water coming out of the overflow pipe is not necessarily related to boiler/CH problems. 

The answer to most of that is, er, I don't know. I'm not really familiar with system boilers, tbh, but since they tend to have external pumps and EVs, then I guess it makes sense they have ditto Pressure Release Valves too. But I don't know.

Make and model, Albe?

As for the PRV on the Megaflo pipework, I'd have thought there would be two, one for the sealed 'system' - boiler, rads, heating coil - and another for the Mega itself. I presume it empties via a tundish so any discharge can be seen? If there's only one tundish, can you trace the pipe feeding into it and see if there could ultimately be two?

It is a WB Greenstar 18Ri.
Just had a look at the manual and no obvious reference to a pressure sensor in the boiler itself, or to the necessity of having an external one.
However now have had another look at the set up  and I think I have found what I was wondering about,
There is a Pressure Relief valve underneath the CH EV, next to the pressure gauge. The pipe after the PRV leads to the pipe that goes outside.
There is another PRV on a pipe coming from near the top of the Megaflow cylinder, that leads to a tundish and then into the pipe going outside.
So both the CH and the cylinder have separate PRV's that discharge into the same pipe that goes outside.
This would indicate that probably the boiler does not have its own pressure sensor internally, hence the necessity for an external PRV.