Pressure increasing after rad removal

[beatts]

Hi,

I recently removed a radiator to allow the wall to be plastered. I closed off the lockshield and the other valve before removal and all was ok, I also checked that the heating still worked fine with the rad removed which it did.

The radiator was off the wall for around 6 weeks and I put it back on yesterday. I refilled it as normal (opened both valves and bled it, refilled via the filling loop to just over 1 bar. All looked ok.

Left it for an hour to see it there were any leaks then put the heating on for 20mins. All was ok. I failed to check the gauge during this time.

I did randomly check the gauge a couple of hours later and it was up at 3 bar!!

So I bled some water from the radiator to get it down to 1.5bar. I also checked all the other rads around the house. An upstairs one had air in it so I bled that out.

Pressure was now down below 1 bar so I topped it back up to 1.5b

Left it for a while and it was stable at that pressure

I put the heating back on for another check amd the pressure started to climb back towards 2-3 bar. So I switched it off.

An hour later, it has settled back to around 1 bar

Prior to the removal, the pressure was always stable around 1.5bar



What do you think the problem could be?

It is a Baxi duo tec combi e40 HE, and probably 20yrs old.


Thanks in advance

 

[Wayners]

Presume will increase when heating is on.
Mines on 1 bar cold.
Goes up to around 2 bar with heating i guess.
Any problems with high pressure you may need to pressurise the expansion vessel or you have a faulty expansion vessel

 

[endecotp]

I suppose if the expansion vessel is going to fail, it might do so when the system has been depressurised and then repressurised.

It’s not just the filling valves passing is it?

 

[beatts]

It is definitely not the filling loop as it stays consistently at 1 bar when cold. Only when the heating is on does the pressure increase to 3bar.

What would the cost of a new expansion vessel supplied and fitted be (approx)

I suppose I should also think about replacing the aging boiler.

 

[polesapart]

It is more likely that the exp vessel needs recharging than replacement.

 

[terryplumb]

I assume you were not using the central heating system during the 6 weeks the rad was removed ?
If so, it would appear that the removed radiator was originally full of air and acting as an EV (expansion vessel).
Your EV may just need recharging and may not need replacing.

 

[beatts]

Yes we didn't use the heating during those 6 weeks, but I think that particular rad was air free prior as I check for water flow at the bleed valve before removal and water flowed immediately.

I will say though that a towel radiator upstairs had quite a bit of air in it when I went round and checked all the rads after refitting. Could this one have acted as an expansion vessel?

 

[terryplumb]

Any radiator that has a fair bit of trapped air in it can.
As heating is in use, the heated water expands and the pressure in a sealed system increases. As the air is compressible it accommodates the expansion( that is the usual job of the EV).

 

[beatts]

Perhaps my expansion vessel has always been knackered then and the towel radiator has been taking up the slack.

 

[terryplumb]

Quite possibly

 

[CarloHeatingEng]

Nobody's answered your cost question. ~ £200-£300 supplied and fitted. There's a five minute check that tells you whether you even need that though. With the system at zero pressure, put a gauge on the schrader valve on the vessel. If it takes air and holds, it only needed recharging. If water comes out, the diaphragm's gone and it's a replacement.


Don't let a flat vessel talk you into a new boiler. That's exactly the moment people get sold one.


And keep an eye on the pressure relief valve now you've had it up at 3 bar. Once they've lifted they don't always seat again, and then you're chasing a slow drop that looks like a leak.