baxi 551 back boiler : no hot water

[damo6969]

Hi I have a old baxi back boiler that has stopped producing hot water. The system is pumped fed heating with gravity fed hot water. The heating works fine but the hot water has stopped working. I have tried my timer on hot water only and water/heating and still the same problem. If i put it on water only and turn boiler thermostat up to maximum the boiler lights and pipework to immersion tank gets very hot but after a fex minutes the boiler goes out. If i turn boiler themsostat down nothing happens at all. I have checked small header tank in loft and this is full of water. I have also tried heating water using immersion heater and this works fine. I am thinking or maby hoping that the problem is just some king of blockage but really need any advice out there. Also forgot to mention that if i turn boiler control up to maximum sometimes i get quite a blast of water come out of overflow pipe in small header tank.

Many thanks please help Damon

 

[oph]

My thinking is that your last sentence has summed it up. You prob have a blockage in your primaries either to or from the cylinder or the cold feed on the system which on a gravity system will be above the cylinder return on the coil

 

[damo6969]

when you say above cylinder return on the coil would that be in my loft then

 

[oph]

when you say above cylinder return on the coil would that be in my loft then

No. Your hot water cylinder in your airing cupboard will have two inch size piipes coming out about half way up on one side and then , on the same side, lower down. This pipe Tee's and will have a 15 mm pipe going up to the bottom on your header tank in the loft ( the small one). Its most probably blocked on that tee

 

[damo6969]

Thanks for your help on a night shift tonight so will have a look tomorrow, is there anything I can buy to put in system to try and clear blockage or do I need to split the pipework

 

[oph]

Thanks for your help on a night shift tonight so will have a look tomorrow, is there anything I can buy to put in system to try and clear blockage or do I need to split the pipework

You wont unblock with a chemical. If its solid then the pipe needs to be cut out and a section replaced.

Be careful mate if your going to attempt this yourself or it will end in tears