Baxi bahama no hot water + banging

[irelandy]

I have a baxi bahama 100 combi gas boiler....it has been banging and locking out when I put hot water on....accompanied by a quick build up of pressure in boiler, and pressure release valve trips..I replaced the diverter valve, now I get scalding water for 20 secs and boiler trips out and will not refire. Any suggestions would be greatly appreciated..thanks

 

[ChrisR]

Central heating? Pump?

 

[irelandy]

central heating and pump both working. problem only occurs when i try to get hot water

 

[kevplumb]

definatley need to stop it banging don't want them things breeding

sec heat exchanger

 

[irelandy]

heat exchanger is clear on both sides ...water passes with no resistance. Nice joke though

 

[kevplumb]

..accompanied by a quick build up of pressure in boiler, and pressure release valve trips

says to me the water aint going round

 

[Agile]

Er... Which heat exchanger?

And what about the DHW NTC ?

Tony

 

[irelandy]

thanks Tony ..the water to water heat exchanger....this is fine when I put radiators on on their own, but seems to stay roasting top part when I try DHW, and freezing cold at bottom. DHW doesn't heat, and upper part over heats and trips out...sometimes accompanied by a quick pressure build up...then pressure release valve trip and lock out. Thanks

 

[kevplumb]

when I try DHW, and freezing cold at bottom. DHW doesn't heat, and upper part over heats and trips out..

its full of gunk

 

[Agile]

I have asked "which" heat exchanger but did not get a proper reply!

All your symptoms indicate a totally blocked SECONDARY heat exchanger!

Tony Glazier

 

[ChrisR]

Quite - or a pipe TO it.

 

[irelandy]

My heat exchanger is exactly as Kevplumb described...cold at bottom and scalding at top then pressure build up and trip out...I've had the exchanger out and she's clear both top and bottom.....we checked the pipes too.. and a fitting with many inlets/outlets and it all seems clear??
Really appreciate all of your advice here..thanks again, Andy

 

[kevplumb]

its clear through part but i would think the smaller waterways are blocked

hence it not heating properly

 

[irelandy]

That sounds like it...going to get some fernox and try to get it clear....must be in there somewhere....will report back when we check that out....this is a wonderful forum...thanks for all your help so far, Andy

 

[Agile]

Nowhere has he actually said if he is taking out the primary or secondary heat exchanger, just keeps on repeating " the heat exchanger is clear" I would love to know WHICH ONE !

Tony