Central heating pressure loss and pressure spike when HW on

[Davie1888]

Hi there, just wondering if anyone can help with a couple of queries.

Firstly I have a small leak by the looks of it, i'm having to top my system up at least once a week via the filling loop, luckily it has been left connected losing approximately 0.5-1 Bar over a week, going by the tiny amount I need to top it up with it looks to be pretty small

I've had a quick look around the system but can see no signs of any leaks around radiators.

I have noticed under the boiler on what I think is the central heating loop supply and return valves signs of verdigree and black deposits which I take it is crap from within the system so would I be right in thinking these could be likely culprits??

I'm planning to get the boiler serviced over the next couple of months so would it be wirth while getting these either changed out or cleaned up and PTFE fitted to the threads.

Another query is the system seems to flatten itself when not in use, I'm not sure if this is just due to the ambient temperature during this time of year as when it's up and running and upto temperature the system pressure sits around 2 Bar?

Finally just out of interest when we have the boiler up and running supplying central heating and we open the hot water system I see a pressure increase on the gauge of around 0.5 Bar, not sure if it should do this it's just something I've noted when i've been in there. I know the central heating loop is isolated when you switch the hot water on but i just thought i'd ask the people in the know just in case this is something to do with the pressure loss just in case somethings passing somewhere.

Any help much appreciated

Davie

 

[45yearsagasman]

It would be helpful if you could tell us the make and exact model of your boiler.

 

[mysteryman]

Get someone to check the pre-charge pressure on the expansion vessel with the system pressure at zero.

 

[Davie1888]

Hi guys thanks for the response, the boiler is a Baxi 105E.

I take it the expansion vessel needs to be pre-charged to stop the system from flattening?

 

[Davie1888]

Ok guys I took the front cover off just for a wee looksie there and can't see anything obvious.
From what I read in the manual the expansion vessel is behind the boiler and it was precharged to 0.5 Bar. I see a pipe which I think is from the expansion vessel and goes down to the supply or return CH line. Im not going to give this a bash myself but any ideas where you recharge the vessel through.

I did have to replace a knackered TRV a while back and flattened the system to do it, I'm used to the older system with a F&E tank in the loft so I didn't shut I the supply and return lines at the boiler so could this explain the vessel flattening if indeed it is flat??

 

[Davie1888]

Second thoughts ignore that about the TRV, the system worked fine for ages after that, this fluctuation in pressure is only recent.
Could it be down to the cold temperatures dropping the system pressure below 0.5 when offline meaning the expansion vessel emptied?