Vaillant turbomax 824e dhw fluctuates hot & cold

[JonJonSm1th]

Vaillant turbomax 824e dhw fluctuates hot & cold

Hi

I was wondering if anybody can advise about a problem that my parents are having with their boiler. When you open the DHW tap the boiler fires up and you get hot water (the temp on display climbs into the late 80's then the boiler switches off (not complete switch off - i.e. is not fired up) water temp drops to lukewarm and display drops to 40's then fires up again and continues this cycle whilst the DHW tap is open. DHW temperature selector has no affect on water temp. at any setting.

The system is pressurised to the correct setting (in the green just above the no.1)

The diverter was replaced 8 mths ago because it was leaking (unrelated to above problem).

The flow rate is at 7 litres p/m.

The CH works fine and the checks mentioned regrading the DV mentioned in other threads do not point to the DV (leaving heating off and checkin if rads warm up on DHW demand). when the DHW tap is opened whilst CH is on the same problem persists.

The boiler is at my parents house who are pensioners. they have had some engineers out but the advice/causes ranged from :-

(1) Thermistor (£90)
(2) DHW Heat Exchanger (Secondary) (£175) + A TF1 Filter (£120)
(3) Gas Valve (£150)
(4) PCB (£225)
(5) Divertor Valve (even though its already been replaced) (£130).
(6) PowerFlush to clean the heating system (this will not solve the problem but is beneficial to have done one guy said (£450 + VAT)

Not going to attempt to fix myself but wanted to know which cause is the most likely problem and I will go with getting that fixed first.

Or should I just buy another boiler ? (not ideal but its probably cheaper for my parents with some of the quotes above).

turbomax 824e installed 5 years ago through a heating grant.

Thanks and regards

Jonathan

 

[spraggo]

The hot water micro switch position needs adjusting, if you open the lower door and drop down the inner grey panel (that is held up by two knurled screws to the top right and left of it), using a torch, you can locate this microswitch at the back and to the bottom right hand side of the casing. When you turn on the hot water you will see that a lever on the right hand side of the diverter valve will attempt to drop down and activate this switch. obviously this is not happening because the micro switch needs repositioning (moving up to make contact with the lever).

This done by loosening a very small screw with a phillips scewdriver to re position it.

 

[Beerlover]

Spraggo, I think you may confusing this with the original turbomax - this is a turbomax plus

IMHO it could be one of three things :-

1. blocked plate heat exchanger - likely
2. blocked main heat exchanger - possibley
3. flow ntc shorting to the casing - rare

Does the return pipe form the pump remain very hot after the flame has dropped back? Does the temperature on Ch rise very quickly in the display after about four minutes? With the combustion door cracked open slightly does the boiler run normally?

 

[spraggo]

Spraggo, I think you may confusing this with the original turbomax - this is a turbomax plus

You are correct, I got the 842E mixed up with the 242E, thanks for pointing this out

 

[spraggo]

Further to Beerlovers correction I have in the past fitted a new diverter valve to the 842E and even though it was new it was sticking and had to be replaced

 

[Beerlover]

No need to get PMT over this, just trying to help

 

[Bunnyman]

Definate option 2 matey **** in dhw ht exch so change it get system cleaned or possibly ok to fit exch an go with spirovent magnaboost2 which is better than tp1

Untitled

• Bunnyman
• 26 Mar 2010
• 499