Increase in pressure of heating

[nero44]

No, there should be no water. Leave it for a while though - MI/regs state that it shouldn't be left connected anyway - as a passing valve can be a very slow and tiny leak, doesn't take much to increase the system pressure.

Got a similar issue.... how long would you reckon to wait? Also, if the pressure increases only when the central heating is/has been running, would this exclude a leaky filling loop? Presumably a leaking filling loop would also increase the pressure even though no central heating has been used? I need to periodically relieve some pressure on my system, but much more so during cold days where heating is used significantly more.

Apologies to OP for topic diversion...

 

[Stuckinarut]

Sounds more like an expansion issue

 

[nero44]

Ah, just noticed mods moved this into its own thread...

Some background:
~Very old Vaillant Ecotec plus 831, 2005-2011 range, with output 24.4 kw / mostly microbore pipework / 6 medium and 2 large rads
Been only living in this property for just under two years, but had to have boiler repairs done already twice.

First time was general servicing, leaky airvent and pressure issues. The boiler would overpressure and then the safety mechanism would kick in self drain the system. This was with Error code. The engineer fixed the flue, resealed and cleaned the system.

Second time (9 months ago), the boiler started to overheat (80degrees flow temp), whereby it would just shutoff. After letting it cool down 5 mins, it would work again. Engineer removed tons of sludge, replaced pump and seals, replaced plate heat exchanger, replaced canoe filter (it was actually missing completely). I do remember him talking about getting a new expansion vessel, but I can't see it on the invoice.

Anyhow, system ran fine for a few month, but I started to see pressure build up again. We don't use central heating much, so this only became apparent in the winter when using central heating much more. And this is still currently the case. Everything is working fine, but with more frequent central heating use pressure builds up from 1.5 bar to around 2.8 to 3 bar so once a week I drain the system to bring it down to 1.5 bar.

Sometime in the next 12-18 month I am looking to do a kitchen extension so then the idea would be to get a brand new boiler, rather than throwing down more money to fix this 15 year old thing...

Does this sound like it could be a leaky filling loop? Or does anyone have any other ideas?

 

[Johntheo5]

Post a photo of the filling loop, some combis have a "permanently" connectd piped filling loop as distinct from one with a flexi hose.

 

[nero44]

Will do this evening. My filling loop is a flexi. Unfortunately the pipework has been boarded-up right to the bottom of the boiler making access to the flexi itself difficult, as its kinda pushed back to the wall. Maybe that's why nobody checked it properly in the past. The engineer did mention at some point he might need to cut into the boarding, which I said is fine as it is in a utility room. But then he never did.

Is a bit annoying as my pipework and rads are quite old (some of the old rads I already replaced), but I reckon there is lots of sludge in the system. I added inhibitor when I got a new rad in a few weeks ago, but obviously with my weekly bleeding, it will have diluted by now.

 

[Madrab]

Presumably a leaking filling loop would also increase the pressure even though no central heating has been used?

If the pressure rises when the CH/Boiler is off then one of the causes could be a filling loop that is passing yes. Only way to check is to disconnect the braided hose.

Everything is working fine, but with more frequent central heating use pressure builds up from 1.5 bar to around 2.8 to 3 bar so once a week I drain the system to bring it down to 1.5 bar.

This would be more prevalent of an EV issue but when the system is off and cools down then the pressure should either return to where it was or if the pressure relief valve opened (check if there is a 15mm copper pipe out of the outside wall in the boiler location and see if it dripping) then the boiler pressure would usually drop to 0 and needed topped up, not stay high and pressure released as that would bring it back to the first point.

 

[nero44]

the pressure relief valve opened (check if there is a 15mm copper pipe out of the outside wall in the boiler location and see if it dripping) then the boiler pressure would usually drop to 0 and needed topped up, not stay high and pressure released as that would bring it back to the first point.

This is exactly what happened the first time. After the engineer attended, this did not happen anymore.

Now, the pressure goes up by say 0.3-0.5 bar when central heating is used and drops down again when cooled down.This I reckon is normal. However in my system over time it slowly goes up, such as that the CooledDown state creeps up to 2.6 bar and then goes beyond 3 when the system is running full steam. Once off, it goes down to 2.6 again, but usually that is the time I bleed it back to 1.5 (cooled state).

Attached some pictures, but you can't really see much as it's boxed in.

The is a flex going through the back from one side to the other, not sure you can see it on the pictures

 

[Johntheo5]

Time for action, post #6 states quite clearly.....
"Only way to check is to disconnect the braided hose."

 

[Madrab]

he might need to cut into the boarding

No need for that - there are obviously screws down the left so chances are the whole panel just unscrews.

 

[nero44]

owkey...

board removed. It was dripping indeed, from both sides!


More so from the left side than from the right. I've recorded a one minute video to illustrate the amount to drip, you need to have audio enable to listen for the drip.

I suspect this should not be the case? the flexi also looks quite old and I did not see any rubber gasket inside, but will check again. It was not leaking while mounted.

 

[terryplumb]

Fit a couple of blanking cap nuts and seals,one to each valve. And see if the pressure remains stable.
Long term the valves would need to be replaced.

 

[nero44]

Thanks Terry, all done now.

In case anyone reads this in the future >> Vaillant Ecotec plus 831 with two different sized filling loop ends require a 1/2" and 1/4" cap.

I've reduced pressure back down to 1.5, then went around the house to bleed all the rads, and now down to 1.3 as my baseline. Will keep it monitored now for a week.

Regarding valve replacement, is this something I can do myself or best to get a plumber in? I assume I don't need to touch any gas lines etc. Just switch off and isolate, drain system, replace parts, refill, check for leaks? It appears the whole set can be purchased on eBay.

 

[Harry Bloomfield]

Regarding valve replacement, is this something I can do myself or best to get a plumber in? I assume I don't need to touch any gas lines etc. Just switch off and isolate, drain system, replace parts, refill, check for leaks? It appears the whole set can be purchased on eBay.

Yes, you can DIY. You would probably get away with it, without needing to drain. Just make sure all bleed valves, etc. - anywhere that air can get into the system are closed, release the pressure by removing the mains input end of the flexible, allow the pressure to drain off, then fit your new valve.

 

[nero44]

Ok so, it has not been quite a full week yet but it is pretty evident that the leaking filling loop valves are the culprits. The pressure is still at 1.3 bar in a fully cooled state, so leakage into the CH system after I've capped off the valves. This is a reassuring results.

I've already ordered the replacement parts. I believe all parts come with washers/seals and olives for the copper pipe connections.

Do I need to buy myself some jointing paste when I make the connections to the copper pipes?

 

[Harry Bloomfield]

Do I need to buy myself some jointing paste when I make the connections to the copper pipes?

You shouldn't need it usually, but maybe get a roll of PTFE tape. If you are just swapping one leaky valve, for another, you might get away with it, leaving the olives in place, undisturbed - just fitting the new valve(s). It might be prudent to wrap a couple of turns of the tape, just around the olive - but not on the threads.