Gulfstream II - unable to maintain water pressure

Hi Mike
I am hoping you can help me. I have a gulfstream II boiler which was working well in the last year apart from losing pressure every few months. In the last 3 days, we have woken up to cold water and the pressure has been found to be 0. We put the pressure back to the red arrow, the boiler fires and we would have hot water for about 20 minutes. After that, the pressure would have gone down to 0 again. I have tried draining the water in the boiler and refilling it but the pressure would fall almost immediately after adjusting it. Do you know what is wrong? Another quick question, what is the red box next to the boiler and what is its function? Thank you very much.

Kind regards
Wiece

Hi wiece,

Apologies for my late reply.

I'm not familiar with the Gulfstream II at all so I can't advise definitively, but this pressure problem is usually caused by loss of water from the system. Water loss can be a plain pipe or joint leak but is more usually lost prom the pressure relief valve (PRV). The PRV opens when the system pressure rises too HIGH when the system is heating up. The pressure rises too high because the expansion vessel has stopped working and either needs re-charging with compressed air or replacing.

I suggest starting by checking the air pressure in the expansion vessel and finding the PRV outlet to see if it is dripping.

Cheers, Mike