Ferroli Optima 901 Combi over pressure & PRV dump daily

[do it myself]

When my system gets hot the pressure rises as I would expect.

But it doesn't stop rising, it just keeps going till it gets to 3.2 Bar & PRV dumps the pressure down to 0.

If I turn my hall thermostat down to 18-19 deg in the hall it reduces the problem & it may only happen once every couple of days but if I turn the thermostat up so the system is running for longer and hotter it may only last a couple of hours.

I have tried lowering the boiler temperature thermostat from max to Norm, it helps but the rads dont get nearly as hot as they should and it still eventually blows the PRV.

This problem was already on the system when we moved in last year.
Just before we moved in they had had a new pump fitted, could it have anything to do with that.

I see messages re: diaframs & air pressure, but dont understand enough to find it or know if it is that.

All the rads have themostatic valves on but I have removed a few to give the system a clear run & it is still the same.

Thanks in advance.
Phil

 

[do it myself]

Have just had a look around & found there is a cut in a piece of silicon pipe running from the air ressure switch it has left a hole abot 3mm wide & has a little dust on the inside of the pipe where it looks like it could be sucking air.
Could this be the problem?

Has the pressure swirch been damaged or can I just replace the pipe.

 

[mave]

It sounds a bit like the problem I posted about recently. Could it be the expansion vessel is shagged?

 

[AnonymousImport]

The piece of silicon tubing won't be the problem, but if you can cut out the hole and the tube still fits do it because this will save you problems in the future. As for the system pressure, gathering from your description the pressure only rises when the system heats and not when it is cold. If this is definatly the case then the expansion vessel ( big red tank) is almost certainly at fault. I would get it changed before the winter because the more you have your heating on the more it will happen. The reason it lasts longer when you turn your stat down is that the burner stays on for shorter periods thus not heating the water as much. You can reduce the blow offs by turning down your boiler stat, this is only a temporary measure untill you can get it fixed. A low boiler stat setting will not see you through the winter.

The job is better done by a professional.

Hope I have been a help

 

[do it myself]

I have been monitoring the pressure since friday.
Turns out pressure also rises when cold, although not up to 3 bar (probably about 2.5)
Came to the conclusion my top up was probably leaking. Stripped it down yesterday & yes when closed, water is still coming thru. This would build up when cold & when the heating comes on it pushes it past 3Bar & the PRV dumps.

My pressure now keeps dropping to zero instead of 3 bar but I do have a drip out of the PRV.

I have come to the conclussion the leaking PRV was disguising the fact my top up tap was leaking into the system raising the pressure.

Replacing the valve today will let you know if it fixes all my problems

 

[AnonymousImport]

Sound to me like you have found the cause of the pressure drop. If that dosen't work you'll be looking for a leak.

Good luck

 

[do it myself]

Oh well didnt work.

I havent been around weh the PRV is dumping but if I set my pressure at 1.5 Bar (Cold) then turn on my CH it get very close to 3Bar

How much of a pressure rise should I expect form cold to hot & where to I find the expansion vessel/diafram.

I have had the bottom cover off & cant find anything, is it in the actual boiler where all the flames & stuff is, cos that looks too dangerous to be taking those covers off.

Thanks in advance
Phil

 

[corgiman]

might have already been said but sounds like the expansion vessel

NOT a DIY job get a engineer in

 

[do it myself]

I have found the expandion vessel round the back of the boiler with a bicylce tyre valve near it. I have tried pressing the valve in but there is no release of air,

Anything I can try before I call a plumber.

Edit- -
Have just found this on a previous post, can I try this

To repressurise, you must first check the air pressure in the expansion vessel. It has a car tyre type connector.
Before you check the air pressure, depress the valve to see if any water comes out, if it does you need a new expansion vessel. This is an important component!!!
The pressure should be 0.5 bar for a two storey building. There should be a connector on the boiler with a non-return valve and near it should be an outlet from the cold water feed pipe, which has a stop valve on it. The two are probably connected by a flexible braided pipe. (they shouldn't be left connected to avoid backflow into the water main)

Next slowly open the stop valve until the water pressure gauge shows 0.7bar when cold (for a two storey building) That's it.

Thanks again