Big pressure swing - 1 to 3.4 bar on Vaillant Boiler

[adrian_ros]

Hello.

The pressure measured on our Vaillant ecoTEC plus 630 reaches 3.4 bar. The target flow temperature is set at 61 degrees.

The pressure with the system not working (boiler and pump off) is 1.2 bar. After 30 mins pressure goes to 3.0 bar, after 60 mins to 3.4 bar.

This swing from 1.2 bar to 3.4 bar is not normal, right? What's the typical min-max pressure range for such boilers?

Ok, now a few questions please. Could there be an issue with the expansion vessel? I read that there a TRV valve is supposed to open at 3 bar. That does not happen, looks like.

The boiler has been serviced by PlusHeat about 2 months ago, but the contractor didn't stay long enough (1 hour) to check the pressure. I don't think he checked the expansion vessel. Is that something that shouls have been checked?

How serious is the situation? Should I call PlusHeat as a matter of urgency? Any advice?

To note, the boiler has episodes when it stops working because the pressure is too low. That's why I cannot bleed the system - it will go on the other extreme, where the boiler won't start (F.22 low pressure).

Many thanks!

PS Setup is with this Vaillant boiler and a big MegaFlo water cylinder.

 

[CountryFan]

No it’s not normal and you do indeed have an expansion issue. It’ll operate a PRV (pressure relief valve) not a TRV (thermostatic radiator valve). As to whether it should have been checked depends on what’s included in their service - seems like it perhaps should have been: https://www.plusheat.co.uk/boiler-service/

 

[Jurassicspark]

Either expansion vessel flat (requires a recharge), or it had seen better days and been punctured. If it's the latter then it will need replacing.

When you mention TRV, I suspect you're talking about the PRV (pressure relief valve), and by the looks of it that's doing its job and letting water exit the system, reducing the pressure, which is why you're eventually see f22 on the boiler.

Repeatedly causing the PRV to lift can result it being stuck open, so it's better if you get it inspected, though that should have been carried out during the "service".

 

[Agile]

I would expect any competent service engineer to ask questions about the pressure to see if it needs further investigation.