Glow-worm Ultracom 30CXi water temp fluctuating

Right, follow this link if you don't have your manual.

http://www.glow-worm.co.uk/literature/

1st Lets confirm that there is definitely a blockage problem. On page 51, follow the instructions to access the D codes. With the hot tap running check D40 & D41 there should be no more than 20 ° difference. If greater than this there is definitely a blockage and we go to the next step.

2nd The instructions for the removal of the plate heat exchanger are on page 61; section 15.25. This is where you now take your pick of the many meethods of cleaning it. BTW there may also be a blockage on the filter shown in Diagram 15.20 - with the system drained it may be worth cleaning anyway, a stiff brush will do it.

Good luck

^^^^ Thanks

Yet another job for the morning.


I'll post back the results


Cheers

Just been looking at those instructions. This is where I regret having the boiler in a larder unit.

Oh well

I've just checked those codes and in a quick 2 mmin check there was a max of 18Deg difference 68-46 Deg between 40 and 41. With a min of 10 deg.

Mpg, I think you mean difference is 22 degrees.

68 degrees is the primary temperature (displayed on the front panel- earlier post). When the flame size fluctuates, is the primary temperature stable?

DP said:

Mpg, I think you mean difference is 22 degrees.

68 degrees is the primary temperature (displayed on the front panel- earlier post). When the flame size fluctuates, is the primary temperature stable?

Click to expand...

Yeah it was getting late.

Ok just checked it now with a fresh coffee in hand.

The front panel says 1.2bar then I turn on the tap and the display switches over to the temp I have set it too "60 deg" I then enter the engineers screens pull up d40 and it says anything from 63-70 deg and 41 says anything from 46-55 deg. I did another quick test and there was a difference of 21 deg. (have to keep flipping between one screen and another)

The temp on the main front panel doesn't alter as it just shows the set temp.

When I turn the hot tap on there is an Initial burst (5 flame icons) seemingly until the hot water hits the tap and then it drops right down and then 2345 5432 2345 5432 and that what you can feel the change in the water temp.


I lowered the set temp to its lowest setting 40 Deg and its still the same.


Thanks again

I initially suggested that it MAY be a blocked plate heat exchanger.

The d40 and d41 do not indicate that its seriously blocked. The differential varies according to DHW flow rate and temperatures but 15-20 C is typical.

Unfortunately, if for a moment we assume that its not the plate then we need to consider what it actually is! That is easier said than done.

An engineer would check the stability of the gas supply, check the temperature sensors for dirt buildup or any other cause of poor heat transfer and if nothing was found to be wrong then do a thermal survey of the boiler to see if this gave any clues.

The latter test is quite difficult to do when the temps are varying and its possible that the measurements which will indicate the problem are within the fluctuations. The sensors also need to be checked for calibration with the boiler at a constant temperature, that is when it has not been used for an hour or two.

If that does not indicate the problem then I would have to use more advanced techniques to partially stabilise the boiler operation. These could include stabilising the gas valve output, replacing temp sensors with fixed resistors etc. Eventually the problem will be found because its only a boiler!

It could still be that the plate is partially blocked and that is sufficient to cause your problem. Normally only a manufacturer's engineer who sees several of that model every day would have a detailed knowledge of how they behave. The rest of us see many different models and know how they behave in the generality but not each model in detail.

There is also another fault mode in plate HEs. Usually the primary becomes blocked and results in a high primary differential. There is also a less common problem caused by poor heat transfer. This can be a surface deposit on primary or secondary sides. This gives a normal differential but elevated primary temperatures and low secondary temperatures. Thats why I measure all four ports when fault finding.

I am also somewhat concerned that you may be getting false results because your flow rate is low. Its normal for an engineer to check the boiler with the full rated DHW flow rate. Then to reduce the flow rate to about a half to ensure it remains stable.

Tony Glazier

Thanks Tony.

Looks like I'll get a man in then.

Thanks
Matt

Is it worth going down this route. Or an independant

http://www.glow-worm.co.uk/service-and-technical/service-packages/