Luke78
Gas Engineer
- Messages
- 28
Hello again all:
Firstly: Personal background, as I know people are likely to ask:
1) I AM GSR
2) Most of my work so far since qualification has been on pipework, fires and cookers with the odd boiler service.
3) At the advice of other members I have made arrangements to go on the Baxi fault-finding course, but couldn't get a date until September...
4) I have done a couple of model specific courses with Worcester Bosch so have some sundry grounding in the innards of boilers.
Hope that explains the level I am coming from!
Having said all of the above, I have so far found forum members to be extremely helpful and am very grateful of any and all help and information.
I have done a search but couldn't find anything directly related to my query, however am happy to be directed to any known pre-existing threads.
I have been requested to service a Baxi 105HE, (haven't visited the property yet) and am trying to get as prepared as possible; manual gives good clear instructions, with pictures and everything, so that in itself shouldn't present any difficulty, but...
Query 1: Manual does not appear to specify any combustion figures in service schedule... Guessing this is due to age of appliance and requirements at the time...
Do I just ensure the appliance is within the 0.008 ratio?
There are no instructions given for adjusting CO2 at gas valve or throttle etc as I have found and experienced on WB boilers in any case!
Query 2:
Customer reports DHW from taps only
gets hot if run at "nearly full pressure", takes 30 seconds - 1 minute to get hot and sometimes goes cold again before heating up properly...
Without benefit of in depth fault finding training I have studied manual and reasoned as follows:
As hot water is eventually provided problem lies either with DHW heat exchanger being furred up, or with sensors that call for DHW?
According to manual, sequence is that flow from hot taps operates the DHW flow switch which then prompts the diverter valve to change to the DHW supply position...
This I understand...
What I am struggling with is why it should go cold again before then going hot. I vaguely recall this scenario being described on a WB training session and think it may relate to a DHW flow sensor defect, but have referred to my notes (now 12 months old plus!) and can't find any direct reference.
Possible theory is that filter in DHW flow switch is clogged? Perhaps causing it to initially detect flow and then after initial flow decreases (owing to valve being partially blocked?) it no longer senses demand and therefore rest of system thinks demand has ended...
Or there is a fault with DHW flow switch itself?
Would like to help customer if I can and unfortunately won't have training for another few weeks yet!
Would be grateful if anyone could point me in the right direction, or even just tell my reasoning is flawed!
What should I be checking?
Any help and replies much appreciated.
Firstly: Personal background, as I know people are likely to ask:
1) I AM GSR
2) Most of my work so far since qualification has been on pipework, fires and cookers with the odd boiler service.
3) At the advice of other members I have made arrangements to go on the Baxi fault-finding course, but couldn't get a date until September...
4) I have done a couple of model specific courses with Worcester Bosch so have some sundry grounding in the innards of boilers.
Hope that explains the level I am coming from!
Having said all of the above, I have so far found forum members to be extremely helpful and am very grateful of any and all help and information.
I have done a search but couldn't find anything directly related to my query, however am happy to be directed to any known pre-existing threads.
I have been requested to service a Baxi 105HE, (haven't visited the property yet) and am trying to get as prepared as possible; manual gives good clear instructions, with pictures and everything, so that in itself shouldn't present any difficulty, but...
Query 1: Manual does not appear to specify any combustion figures in service schedule... Guessing this is due to age of appliance and requirements at the time...
Do I just ensure the appliance is within the 0.008 ratio?
There are no instructions given for adjusting CO2 at gas valve or throttle etc as I have found and experienced on WB boilers in any case!
Query 2:
Customer reports DHW from taps only
gets hot if run at "nearly full pressure", takes 30 seconds - 1 minute to get hot and sometimes goes cold again before heating up properly...
Without benefit of in depth fault finding training I have studied manual and reasoned as follows:
As hot water is eventually provided problem lies either with DHW heat exchanger being furred up, or with sensors that call for DHW?
According to manual, sequence is that flow from hot taps operates the DHW flow switch which then prompts the diverter valve to change to the DHW supply position...
This I understand...
What I am struggling with is why it should go cold again before then going hot. I vaguely recall this scenario being described on a WB training session and think it may relate to a DHW flow sensor defect, but have referred to my notes (now 12 months old plus!) and can't find any direct reference.
Possible theory is that filter in DHW flow switch is clogged? Perhaps causing it to initially detect flow and then after initial flow decreases (owing to valve being partially blocked?) it no longer senses demand and therefore rest of system thinks demand has ended...
Or there is a fault with DHW flow switch itself?
Would like to help customer if I can and unfortunately won't have training for another few weeks yet!
Would be grateful if anyone could point me in the right direction, or even just tell my reasoning is flawed!
What should I be checking?
Any help and replies much appreciated.