baxi bahama cutting out

[cradoug]

my mother in-laws baxi bahama 100 (worst boiler inflicted on the general public)is giving me no end of grief. It started out only running for a few seconds, both CH & HW and then cutting out. I replaced the CH flow switch and that cured the problem. Now I have 2 problems:
1) the pressure swings high and low. I depressed the schrader valve on the expansion tank and air came out (no water)so it looks like that's ok. When checking the pressure on the expansion tank, what should it be and do you check the pressure at the schrader valve or do you rely on the system pressure???
2) the second problem is that it intermittently cuts out while running CH only(flame failure light comes on) I think this may be that the boiler is overheating. I'm never around when it happens, so I cannot comment on the state of the boiler at the time. Can anyone Help??

 

[baxpoti]

Check expansion vessel pressure with no system pressure (0 on gauge)
Should be around 13psi or 1 bar.

C/h problem could be gas valve related
check low gas pressure setting 2.3mbar minimum

 

[pannierstan]

Check expansion vessel pressure with no system pressure (0 on gauge)
Should be around 13psi or 1 bar.

And make sure you leave a drain point open when you pump it up

 

[cradoug]

Hi guy's, thanks for the response, I'll resetting the expansion tank pressure and let you know how it goes.

 

[cradoug]

Hi Again, after resetting the expansion vessel pressure, the CH system pressure has settled down.
I still have the problem of the boiler cutting out on flame failure. The boiler will run for hours without a problem and then just cut out on flame failure. Can anyone tell me what temperature the overtemperature thermostat should kick in at?? The gas pressure seems to be stable and the boiler does not seem to actually go over temp.

 

[baxpoti]

105*C overheat stat
What's your low gas set at?

 

[cradoug]

I'll check the overtemp with a thermal gun to see if its operating when it should.
I don't know how to check the low gas setting

 

[micky p]

Good point about low gas pressure i have had this with another boiler before.

I have just had a quick flick throught the manual and it does show you how to adjust the minimun gas pressure unless i missed it. I know one way of finding out the minimum pressure is to fit your manometer to the burner pressure test nipple and open the hot tap. this will give you the max pressure.. then turn the tap down so that it slows the water right down but without it atuallt shutting the boiler off. This way the boiler you eventually drop down to minimum pressure once the water gets too hot. sounds a bit tricky and can be but will give you an idea of what the min pressure is thought. If it needs adjusting whichit should be 2.3mbar then it might be a matter of giving the technical helpline a ring to talk you throught it.

I must say before you do any of the above you want to beecking your inlet working pressure when the boiler is on max. The problem may be elsewhere.

 

[baxpoti]

I don't know how to check the low gas setting

Employ someone who does, messing about with gas boilers is not advisable unless you are competent

 

[cradoug]

Employ someone who does, messing about with gas boilers is not advisable unless you are competent[/quote]

You're absolutely right. I am a machine tool maintenance engineer and competent on elec, mechanical and plumbing. When it come to the gas side it's time for a CORGI.

thanks for all the help!