How do I re-pressurise the boiler via the temporary filling loop

Re pressurise via filling loop,if boiler continues to loose pressure replace the expansion vessel.

Did you bleed the air from the pump ? Sounds like a air lock

check tops of spindles at radiator valves for leaks easy repaired set pressure to .8bar setting at 1.5 may be make overpressure and blow off through high/pressure releasese valve

Identify the cold feed to the boiler, then look for a tap/service valve which when turned lets water into the boiler via a fill loop to pressurise it. 1-1.5 bar is ok
ju

Sounds like the expansion vessel in the boiler has lost pressure or is faulty. If you have a tyre pressure gauge, locate the expansion vessl and check the pressure via the schraeder valve. It should be around 1.5 bar. If there is no pressure you can re pressurise it with a bicycle pump. Should it not pressurise then you will need a new one. The pressure relief pipework outside is damp because the system is over pressurising at relieving pressure at 3 bar. This obviously causes a system pressure drop. You can install a pressure vesel into the heating return pipework should accessing the boiler be difficult.

if your boiler is a combi re-pressurise locate filling loop and refere to manual

I have a similar problem with this boiler. When CH on, boiler overpressurises, (check relief valve outlet) You will then lose water from the CH loop and will have to repressurise when the CH loop cools. The problem is most likely caused by a loss of air from the expansion tank, which will need re-charged. This is not a big job as it has a standard tyre type valve connection but needs an accurate pressure gauge. Probably best left for plumber.

a couple of things , is your filling loop disconected ? , and are all your radiators blead from air, have you got a high point where the air can get stuck in system say pipes going into roof etc you may need to fit a air release valve in line at highest point to remove the air from system , your boiler should be around 1.5 bar running preasure average setting . if you are constanly filling with water you could be exceeding the pressure valve limet which releases pressure from system this could be faulty ?

Hi tiger650,

I'm Harvey the Master Plumber.

Your problem is: The Alpha SY24 boiler has stopped working. The pressure gauge has dropped, you need to know how to re pressurise the system once the radiators have been bled

Every hydronic heating system is required to have a presure regulator. Most guys call it a feeder valve. Every one I've installed or worked on had one. It's job is to keep the water pressure constant by adding water when you release some air without over filling the system. Sounds like it's not working. Some types can be serviced, others cannont so you may have to replace it. If you're not sure what to do it might be prudent to check the Repair Directory for a repairman.

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Thank you,
Harvey your Master Plumber