Vaillant Ecomax 835e Hot Water Cuts Out S53

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Hi, I hope you can provide some advice on an issue I'm having with my Vaillant Ecomax 835e.

When I turn on DHW downstairs, the boiler fires and provides hot water as expected.

But upstairs when the shower or bathtub are used, the water will get (very) hot, then steadly decrease in temperature, either to luke-warm or sometimes completely cold. I've caught the boiler giving S53 status at this stage - "Delay mode due to lack of water in system".

I can improve the issue by turning the DHW set temp right down below 40*C and switching the CH off, but even then I think it still somes does it.


Steps taken so far:
- Pump is set to 100% in the settings.
- DHW heat exchanger replaced with new one.
- CH system powerflushed, as I was concerned that if the heat exchanger had becomme clogged and didn't want a new one suffering the same.

No improvement after the above steps taken.

As this didn't work, I'm reluctant to keep replacing parts at random, and I'm hoping you can help me choose the next step(s)?


Other notes:
- There is a Spirotech MB3 magnetic filter fitted.
- 13 rads, most with TRV's and house is an odd "L" shape, so some long pipe runs.
- I've noticed - admittedly, only recently after the system has been re-filled - that there is a large amount of air bubbles in the water that is bled from the system. Is this just pockets of air being purged out by normal circulation, or is something else going on to generate gas (pump cavitation? corrosion? chemical reactions?)

Thanks
 
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CBW

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Have you considered getting a Vaillant familiar gas engineer in, or even Vaillant on a fixed price repair? Could be a few things.
 
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After a bit more playing with it, I'm now suspecting it's the pump at fault, or... a significant resistance to flow against the pump, within the boiler - i.e. a partial blockage of the main heat exchanger. When the pump is set to "Auto" (presumably runs slower than 100%), I can replicate the fault even on the downstairs taps, which has never happened before. This might also explain why it's worse when CH also running (even more work for the pump).

The Novice, I appreciate your reply and suggestion, yes I have considered it, and given the next steps may involve inspection/cleaning inside the gas bit/main heat exhanger, I won't attempt myself.

However, I'm also an engineer and I like problem solving. :)


I also spotted a couple of installation anomalies (faults?):

1. The magnetic filter is fitted on the flow, not the return (there's no space for it on the return). I presume this means it won't be doing it's job as effectively at preventing debris entering the boiler.
2. The DHW pipe exiting the boiler is 15mm, but becomes 22mm for the pipe going upstairs... When running the upstairs hot tap I hear a ticking noise in this pipe.
 
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You're better off getting someone in that knows what they're doing. Your comments show you don't really understand how the boiler works.
A combi boiler is either in heating or hot water mode. Never both.
Cleaning the gas side of the heat exchanger will have no effect, although there is a seal on it that needs replacement every few years.
Increasing pipe size will not cause this problem.
The most likely thing is a restriction somewhere or a weak pump causing the flow differential to be too big.
 
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Modern boilers like that you cant really poke about yourself and still be safe. It will almost certainly be a fairly easy issue to fix for a vaillant engineer and probably save you a lot of money rather than chucking parts at it. But we can't really give advice on DIY gas work on the forum (which this is the moment you remove the outer white casing)
 
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Don't read too much into the codes...they are generic for the whole range of boilers but AFAIR the diverter can be placed in mid position only for the air bleed program during commissioning/servicing.
 
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OK, fair enough, I've booked the fixed price repair with Vaillant and we'll see what comes of it... I am concerned it'll be the main heat exchanger and £££ :(

Any thoughts on whether I should get the magnetic filter moved over to the return pipe instead of the feed? Can the two pipes be simply swapped over, i.e. do radiators care which way the water flows?
 
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OK, fair enough, I've booked the fixed price repair with Vaillant and we'll see what comes of it... I am concerned it'll be the main heat exchanger and £££ :(

Any thoughts on whether I should get the magnetic filter moved over to the return pipe instead of the feed? Can the two pipes be simply swapped over, i.e. do radiators care which way the water flows?

Typically no, BUT sometimes the Thermostatic Radiator Valves do, you need to look at the TRV bodys and see if they have arrows on them, some can take flow either way some cant, some can but need a setting under the TRV heat altered, they will work the wrong way round but can produce some hellishly loud banging and hammering when on the biting point of closing.
 
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The most likely thing is a restriction somewhere or a weak pump causing the flow differential to be too big.


Are there any really good cleaning agents that I can leave in the system for some time, to see if it will clean up the internals and reduce the restriction?

I am basically expecting Vaillant guy to say it's the main heat exchanger and that'll be another £400 to replace on top of the £285 fee... but if the existing one is not fully blocked, maybe it can be saved?
 
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Hmm, didn't know that, what then is meant by diagnostic code d.35:

Diverter Valve Position, either 0 = heating system, 1 = hot water, 2 = mid-position

That’s not a fault code just a display code to tell you what the diverters doing, don’t take too much notice of all the “experts “ the most patronising bloke on here was grinding his rusty rear discs down in situ on another thread ,yet always tells you to leave it to the professionals...........
 
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Did you manage to get to the bottom of this issue? As I have the same issue with the same boiler..
Sorry to hi jack your thread
Thankd
 
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