Ecomax 824E - Replace Primary HE - can I DIY?

[DWINYARD]

The problem:

EcoMax 824E Vaillant boiler, about 10 years old. Fails regularly and reports error code E12 (differential temperatures too high). Problem happens when hot taps are on (so, taps run hot, then cold, then hot again, etc.). Also happens when Central Heating (only) is on. So, it's not the Plate HE I'm guessing if it happens when CH is on (with all hot taps off).

*COULD* be the pump, except the resistance across this is 170ohms, which, according to Vaillant, means it is operating correctly. Also, with the CH at least, after about 10 mins of E12 on/off, the boiler settles and remains on (output pipe warmed up enough I guess), so this also suggests the pump is fine.

15mm gas inlet. 15mm HW system. 22mm CH system. Problem has arisen recently after 10 years of good working order, so I'm guessing the pipe sizes are fine.

British Gas sent a guy round who also thinks it is the Primary HE. They quote me £600 to replace it.

My questions:

1/ Do experts on here agree from what I've said above that this looks like the Primary HE?
2/ What else could it be, and how do I check for this/eliminate the possibilities?
3/ Can I replace or clean the Primary HE myself? I'm no qualified plumber, but I'm not an idiot either (managed to build a kit car, for example). £600 is a sum I'd like to avoid.
4/ Of the £600 quoted, £400 is the cost of the heat exchange itself. Does that seem reasonable.

Thank you for any help. This is my first post here, so if I've left info out or done something wrong, please be patient and poliely correct me (I've read the FAQs and rules, promise! )

 

[gas4you]

You need to get the flow and return temp readings as the boiler heats up. I think it is d40 & d41 that you should be watching. Check your service manual to confirm.

 

[DWINYARD]

Okay, the manual does not list the Diagnostic codes (helpful eh?). So, I put it into Diagnostic mode and just went with D40 and D41.

Turned on the hot tap. At the point at which the boiler cut out (within about 20 seconds), D40 = 69, D41 = 34.

This makes sense. The error description of E12 is that the difference between the two NTCs is 35 degrees or more.

On a separate note, I see from reading the manual that replacing Primary HE involves disconnecting the burner from the gas supply - and I am not qualified at all to work with gas.

Edit: Once I stop the hot tap, d41 slowly rises up to about 78, then ebbs away again.

 

[gas4you]

With those readings there definately seems to be some sort of restriction in the flow through the HE. Or maybe the pump could be clogged up with crud.

You could get someone to flush the HE out on its own before paying out to replace it.

 

[DWINYARD]

Can it be flushed in-place? From the installation manual (and the replacement quote) it looks like just taking it out and putting it back is a good 2-3 hours of work.

 

[Mr Smyth]

I assume you have some sort of homecare contract with BG? if so I would ask them to change the pump under contract before you spend the £600.

Cheaper option would be to flush the H/E. I spoke to an engineer locally to me who has the attachments to fix a powerflush machine directly in place of the pumphead. He then flushes the main and secondary h/e and says he has a high success rate.

Have you tried simply adding fast cleanse and then cold flushing the system?

Good Luck

 

[Deleted member 105431]

probably plate h/exchanger blocked. best bet get Vaillant in on a fixed price repair (will be around £300 ). 01773 828100

 

[DWINYARD]

Okay I'll call Vaillant, thank you for the number - except I don't believe it is Plate HE as the problem occurs in both CH and DHW mode, and I am satisfied the flow control valve is working.

 

[Deleted member 105431]

Okay I'll call Vaillant, thank you for the number - except I don't believe it is Plate HE as the problem occurs in both CH and DHW mode, and I am satisfied the flow control valve is working.

is the black flexi rubber tube blocked? you should be able to "pinch" it with your fingers and it shouldn't feel rigid or "crumbly"

 

[DWINYARD]

I assume you have some sort of homecare contract...cheaper option would be to flush the H/E....
Have you tried simply adding fast cleanse and then cold flushing the system?

Good Luck

My homecare lapsed - my fault that one. I got fed up of paying year after a year for a faultless boiler. Let that be a lesson to me

I haven't tried a fast cleanse. I buy that from a plumbing specialist, right? Then empty the boiler, put that stuff in, run the boiler a bit, then put some fresh distilled water in afterwards? Sorry to seem obtuse but most of this is new to me.

The BG engineer who came tested the water in the system and said it was good. No sign of carbonate build-up and no iron-filings. He said that was a bit weird, given that eveything else points to a duff PHE.

 

[Deleted member 105431]

check the black flexi rubber tube on pipe to heat exchanger for blockage before u do anything else. these block up causing your symptons (tubes are £7)

 

[DWINYARD]

is the black flexi rubber tube blocked? you should be able to "pinch" it with your fingers and it shouldn't feel rigid or "crumbly"

This is the one on the pipe directly connected to the PHE yes? I can't budge it with my fingers. It's slightly flexible on the near-side, but feels like it's a very high pressure, if that makes sense. My grip can hardly make a change to it. On the far side, it's hard has rock. Feels like it might as well be a solid metal pipe with cladding instead of a rubber tube. What does that imply?

 

[Deleted member 105431]

is the black flexi rubber tube blocked? you should be able to "pinch" it with your fingers and it shouldn't feel rigid or "crumbly"

This is the one on the pipe directly connected to the PHE yes? I can't budge it with my fingers. It's slightly flexible on the near-side, but feels like it's a very high pressure, if that makes sense. My grip can hardly make a change to it. On the far side, it's hard has rock. Feels like it might as well be a solid metal pipe with cladding instead of a rubber tube. What does that imply?

your heat exchanger is fine. you need to either take out and unlock this tube or cut it out and replace it. drain the boiler and undo the huts either end of pipe and see for yourself.

 

[Deleted member 105431]

part number for tube is 080387. (approx £7)

in future a contract with Vaillant 0870 606077 instead of ****ish gas would be a good idea mate.

 

[DWINYARD]

Woot! This is an avenue definitely worth investigating first then! Thanks for the pointer.