Hot water problems with Vokera Excell 80e

[StuM]

Hello, been reading around the forums for a few hours about what this could be but i can't put my finger on it. We have an excell 80e boiler which came with the house we bought - i think its over 1 years old now. Over the years have found it likes to eat diaphragms but on the whole is very reliable.

However, it has always had a problem keeping the domestic hot water temperature correct, infact it often gets scalding hot despite the temperature dial being set to minimum... i'm not sure if it's a sensor or the heat exchanger after looking at other posts.

Also noticed when i open the hot tap, boiler fires up and starts to heat the water, but the flow of water 'slows' a bit.

Boiler's pressure seems ok, stays at 1 bar, other thing I noticed based on previous posts is that the temp dial reaches about 55 degrees and then the boiler cuts out - shouldn't it go to a low flame?

 

[glasgowgas]

if its eating diaphragms, make sure its diaphragms for an excell you are replacing them with

as for dhw temps, water flowrate is vital, as are min and max gas pressure and modureg needs to be checked

gas side has to be checked by an rgi, its not for a diyer

excells are pretty much bullet proof, maybe try Vokera for a fixed price repair?

 

[Agile]

Before the boiler can modulate, the gas valve has to be correctly set up. ( Gas engineer job! ).

The normal operation is for the boiler to maintain the set output temperature by modulating the flame down.

If the temperature gets too high a seperate function shuts off the flame. Thats seems to be happening in your case.

Other than measuring the temperature sensors at various temperatures then I doubt there is much else that you can do. A registered gas engineer would first check the settings of the gas valve as thats a prerequisite for correct operation.

Tony

 

[StuM]

Slight typo in my message, boiler is over 10 years old in my estimation, but yes think it's time for a CORGI guy to take a look as I don't think it's setup right.

I'm okay doing the diaphragms, used proper service kit T0019, but that's as far as I can go I think.

Thanks for the info. Do you think I would be best going through Vokera as they'll know what to look at? I'm just wary of most local engineers who I feel prefer to suggest replacing PCBs rather than diagnosing.

 

[glasgowgas]

how do you know what a local eng would diagnose for your 10 yr old Vokera?

the last thing i would be thinking if i was called out to an Excell would be the pcb

not being familiar with your area, a fixed price Vokera repair would be a good base to get your boiler back up on its feet

after that either a service contract ( not with BG ) or put away a tenner per week for annual servicing

 

[StuM]

Was just meaning that I know the kind of comedians that work in my area based on other jobs I've had done in the past (not boiler/gas work tho)..... basically find people are lazy or inexperienced college leavers that take the "replace it" attitude with most jobs... not saying this is likely to be the case, just my previous experience.


Just looking at gathering some numbers for local engineers anyway, never know there may be a Vokera expert amongst them... one question though, is the Gas Safe Register the new CORGI - if an engineer isn't on the Gas Safe register am I best avoiding them? The Vokera website seemed to suggest that?

 

[DP]

The Excel does indeed eat diaphragms but less so if the replacement diaphragm is fitted after all the ancillary bits and pieces are nice and clean. I often find some just bung in a new diaphragm without cleaning the rubber deposits on the brass sections. The diaphragm lasts longer if the check valve within the domestic manifold is also cleaned to remove rubber deposit.

I usually replace the diaphragms every two years. Any longer, the rubber is stuck to the brass, any less the rubber is healthy.

Boiler should deliver 9.5l of water per minute to raise the temperature by 35 degrees C. If less water passes through the hot water heat exchanger, temperature rise will be greater. In fact the main to hot water heat exchanger compatibility is such that during winter, at stipulated hot water delivery, control circuitry does not even kick in as heat generated is sunk by the hot water heat exchanger. If the burner pressure and gas valve settings are wrong, performance is going to be erratic.

If the central heating is fine and in control, I would assume HW controls to be the same as control element (the thermistor) is common to both functions.

If flow of water reduces, I would be looking at cold water pressures (not boiler pressure as it has nothing to do with hot water at the tap- it is the pressure that is exerted on the radiators)

Get a thermometer to measure temperatures. Temp gauge on the front panel is sluggish. It cannot give you a true picture of actual flow temperature. Temp gauge showing 55, very hot water and boiler cutting out suggest that the hot water heat exchanger is bunged up on the RADIATOR side. It could also be scaled up on the hot water side, but this will need to be qualified by regulars who know about lime scale, a problem that us in Glasgow do not encounter (well perhaps a small amount in Milngavie)