Lack of water in system warning, even though pressure at 1.5

Hi,

I woke up the other morning to find our boiler had stopped working, both the hot water and the CH. It's a Radiant RMA 24E, which I think I'm correct in saying is a combi (as I have no tank in the loft) with a built-in storage cylinder.

The pressure in the CH system was showing practically 0 on the pressure gauge. I tried refilling the system, but it wouldn't hold any pressure, so after a bit on investigation I took a chance and order a new 3 Bar pressure relief valve. After fitting the new pressure relief valve I refilled the system and the pressure held at 1.5 bars (the recommended pressure for the system in the manual).

Fixed, I thought. No. My boiler has a series of 11 lights along the front (for "self-diagnostics", the manual says) and the light that signals "lack of water in the system" was flashing and the light that signals "1.5 bar water pressure in system" was OFF. I wasn't sure how this could be possible given the reading on the manual pressure gauge was just over 1.5 bar, so I order a new water pressure switch. At the same time I also order a new expansion vessel because when I tried to test the pressure of the air, water came out of the valve.

So today I replaced the water pressure switch and also the expansion vessel. I then refilled the system (to 1.5 bar again) and turn it on and... nothing

The only change is that the light that signals "lack of water in the system" is still flashing, but the light that signals "1.5 bar water pressure in system" is now ON, which has left me totally confused because I can’t imagine how both of these things can be true at the same time???

This is the first boiler I’ve ever worked on and I’ve exhausted my limited knowledge of ideas - most of them found from reading this forum, so thanks for the help so far

Any ideas what to try next?

You changed the pressure reliefe valve. Was this letting out water

andytheplumber said:

You changed the pressure reliefe valve. Was this letting out water

Click to expand...

Thanks Andy. I'm pretty sure the pressure relief valve that I replaced was letting out water because when I refilled the system (before the valve was replaced) water flowed out off the pressure relief pipe to the outside world.

Even with the 3bar pressure relief valve replaced, there is still a small trickle of water coming out of the pressure relief pipe, but I had put this down to me opening the 7bar pressure relief valve that shares the same pressure relief pipe (which I think is part of the hot water system), before I read the FAQ that says a pressure relief valve typically won’t seal 100% once opened. //www.diynot.com/wiki/plumbing:faq:faq10

Hope that answers your question?