Baxi 105e dhw heat exchange not heating water

[Jj5966]

Hi guys wondering if someone can help,I've changed diapragm and thermistor on my baxi 105e and now going to change the dhw heat exchange as I'm thinking that's the problem,what do I need to drain Down to change this? Exactly the same as above mentioned parts? How do I drain the combi itself? Thanks

 

[gigz]

What makes you think its the heat exchanger ?

 

[Jj5966]

Hi gigz,well im assuming it is asked a couple of traders on the net and they rekon it is,the heating is working fine its firing up when I turn the hot tap on, diapragm is fine the pushrod is activating the micro switch, only produces hot water when I run the tap very slow, does this sound like the dhw heat exchange? Thanks for your help.

 

[gigz]

Do the lights go all the way to 80, then gas cuts out, comes down then fires up again when taps opened fully ? Or does lights go up to 60/70 and sit there with gas light on all the time ?

 

[Jj5966]

If I run the tap slowly (dribbling out) it will constantly heat water lights go right up,when I open tap fully it just drops right down 1 light max!

 

[Jj5966]

It sometimes just decides to work too,it will work for a few days then go again! Bloody baxi

 

[gigz]

Does the gas go out though ? Usually if the plates blocked it'll light all the way to 80 then overheat (gas goes out) then so on and so on. Best way to tell is the temp difference on the F&R to main hex.

 

[Jj5966]

Thank gigz, yeah it goes right up then knocks off refires then same over, how can I test the temp on f&r and main hex, just quick touch test?

 

[Jj5966]

Is there anything else that it could be? How do I go about draining the pressure out of the combi itself? I changed diapragm the other day switched off gas supply,dws, opened hot tap to drain the pipes but there was still pressure in boiler, how do I release this?

 

[gas112]

With the heating stone cold run the hot top then check if the left hand 22mm pipe coming from boiler (flow) is getting hot if so its a sticking diverter valve

 

[Jj5966]

Hi gas112/gigz,went to test it when I came home from work,all the pipes were cold and typically the only one hot was the 15mm feed coming from the dhw hex,so I jumped in the shower quickly lol turned the heatin on then about 30 mins later and boom not hot water again lol is it a sticking diverter?

 

[Jj5966]

P.s the lights stayed on constantly when I was running the hot water earlier,wasn't knocking off at 80 just constantly staying there nicely!

 

[Jj5966]

Hi gas112,went to test it when I came home from work,ran the hot tap with the heating stone cold all the pipes were cold and typically the only one hot was the 15mm feed coming from the dhw hex to the taps,so I jumped in the shower quickly lol turned the heating on then about 30 mins later and boom not hot water again lol is it a sticking diverter?