Refilling a sealed CH system with the boiler at the highest point

[SpeedTorque]

The situation: Having recently found a leak in a micro-bore pipe, thanks to a plasterboard screw going right through it. I decided to fully drain the system during the repair and fill with a system cleaner to run for a few days and then drain and refill with inhibitor.

The initial problem: Upon refilling the system and bleeding the radiators I switched on the boiler only to hear lots of loud banging, the pressure hitting 4.5bar and an error message translating to "flue over temp". In a panic, I twisted the red pressure relief valve and this reduced the pressure, vented a load of air. When I restarted the system, it seemed to work fine.

The current problem: I now have a working CH system but the pressure drops to 0bar over the course of about 4 hours. There is hot water coming from the PRV so I assume this has not sealed correctly. The system is still full with cleaning agent and will require to be fully drained for:

A, fitting of a new PRV

B, refilling with fresh water and inhibitor

My question: Given the boiler being located at the highest point of the CH system, how can I refill the system safely avoiding the banging and clattering that I experienced last time?

Many thanks

John

 

[Hot&Cold]

A, fitting of a new PRV

B, refilling with fresh water and inhibitor

My question: Given the boiler being located at the highest point of the CH system, how can I refill the system safely avoiding the banging and clattering that I experienced last time?

That installation has suffered a severe breakdown,its covered under any decent inclusive property insurance and should be notified to the insurance company for a fairly free repair.

Every property is different so needs and demands differ,it needs an experienced operative onsite to sort it out.we cannot see your installation but your periodic inspection operative/company will be able to fix it and issue paperwork saying its fixed.

Or you may just get lucky

 

[oilboffin]

You need to pressurise the system and bleed at the highest point on the boiler whoever put the boiler in should have provided a bleed point when installing if not then you'll have to put one in before you fill up.Bob

 

[ReganAndCarter]

Does you mystery boiler (??) have an air vent? Is the cap on it loosened to allow it to vent properly?

 

[SpeedTorque]

Hi, thanks for the responses. The boiler is a Baxi Duo-Tec combi 28 (the one with the dials, not the central LCD screen). On the top of the pump is a brass device referred to in the manual as the Automatic Air Vent. Interestingly, there is another one which is fitted above the boiler protruding from the cabinet between the expansion vessel on the left and the flue exit. This is additional to any other installation I have seen. I would guess this is supposed to get rid of the air in the system but I have no way of testing it's operation, the only operation I can do is to remove the black plastic screw from the top of it. However, given the symptoms described above, I would think these devices are not working?

 

[SpeedTorque]

Reading through the installation manual, I notice:

"IMPORTANT: If the boiler is installed at a high point in the system it is strongly recommended that Automatic Air Vent Kit 720004701 is fitted. Ensure that this vent is open."

A quick search of this reveals something which looks a lot like what is fitted to the top of the boiler. I am sure I removed the black screw on this as I filled the system up, but it is possible I missed it and removed the one on the pump only...