Intermittent cold water (Vaillant ecoTEC plus 937)

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Hi,
We've got an ecoTEC+ 937 that's intermittently misbehaving - primarily while I'm in the shower and giving me cold water :( we're going to call Vaillant out to look at it (it's under contract) but wondered if anyone had any thoughts.

One specific question is where is the 'flow temperature' (i.e. the one normally on the display) taken - and what is that expected to do while the hot water is running.

The system is a fairly simple setup; normal thermostat, no tanks (the one on the boiler is not enabled), normal shower, cold input from the mains. It's a conversion from an old system with some of the original radiators still in, mostly with thermostatic valves.

For your entertainment I've got a video of the control panel during the shower (it's sped up by a factor of 4) showing the flow temp and other status.

http://www.youtube.com/watch?v=K53yjs7e9KQ

It doesn't always do it - but that video shows tonights behaviour:

1) at the start the heatings going quite happily
2) 22:10 (3:30 into vid) I turn the shower on and within 5 mins it's cold; note how the flow temperature as displayed drops down to 40c by the time I turn off at 22:16
3) The flow temperature keeps dropping and eventually it all turns back on and the heating warms up.
4) Later in the video you can see us running the taps again and it heats up for a short while and drops again rapidly - the flow temperature sometimes going under 35c.

The temperature in the shower was cold at about 22:15, today I'd also run a tap and checked it's temperature was also cold - so it's not the shower thermostat. The pressure on the tap and shower is fine.
Note also that the burner is shown as on during that period.
Note also there are no errors displayed (we have intermittently had pressure problems in the mornings and it occasionally needs a top up but none recently)

I had thought perhaps this was only during the really cold nights a few days ago, but it's still doing it now it's warmed up a bit.

Any thoughts welcome.

Dave
 
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Press the I button when your running the tap an it starts to cool, this will give u a status code my guess s53 overheat,,,, blocked hoses ,filter etc search the forum
 
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Press the I button when your running the tap an it starts to cool, this will give u a status code my guess s53 overheat,,,, blocked hoses ,filter etc search the forum

Thanks, I'll try that; although if that was happening shouldn't it have shown that code on the display anyway? (I don't think I spotted it displaying anything on the video).
 
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The display only shows fault codes during normal operation.

I would guess the S53 means "its too hot so the burner has turned off", rather than a "fault" as such but Bunny will advise further.
 
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What does it do when the internal storage tanks are enabled?

Why are they not enabled?

Does the water temperature vary when you run a basin tap, or bath tap?

Is your shower head scaled up or the wrong type, ie for an electric shower, or has an 'economy' flow reducer fitted and therefore has reduced flow?

What HW temperature seeting are you using...it looks very low in the video? You need to avoid Legionella bacterial infection in your system!
 
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U asked for advice mate I've given it, that's the problem, ... As I stated s53 is a status code it won't show any fault codes if it's showing to big a spread between the 2 ntcs
 
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U asked for advice mate I've given it, that's the problem, ... As I stated s53 is a status code it won't show any fault codes if it's showing to big a spread between the 2 ntcs

Hi Bunnyman, thanks for the answer, I hadn't realised that there were two
levels of code, some that weren't displayed by default.

Today was the first time since I posted that I managed to catch it in the act, and it did indeed give an s53 (followed by an S27).

In between, the Vailant eng had visited and he had diagnosed a blocked plate heat exchanger (the one on the hot water side), that I guess makes sense from that; now just to wait for them to order a replacement.

Thanks,

Dave
 
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I doubt it will be a blocked plate heat exchanger, more likely to be either of the pumps, mini PCB, main PCB, loom, blocked hoses, blocked canoe filter or even blocked main heat exchanger. Any of these have been found to cause problems, but have never had to change a plate!

You are probably a victim of a look'n'book by a lazy engineer! I bet it won,t be him coming back.
 
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I doubt it will be a blocked plate heat exchanger, more likely to be either of the pumps, mini PCB, main PCB, loom, blocked hoses, blocked canoe filter or even blocked main heat exchanger. Any of these have been found to cause problems, but have never had to change a plate!

You are probably a victim of a look'n'book by a lazy engineer! I bet it won,t be him coming back.

Well he did a good look at the temperature differences and then checked it with a mate on the phone before confirming that as his diagnosis; so it's at least two of them who are mistaken, and there are at least a zillion people on the web who've had the same problem and ended up replacing the plate.

Dave
 
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I doubt it will be a blocked plate heat exchanger, more likely to be either of the pumps, mini PCB, main PCB, loom, blocked hoses, blocked canoe filter or even blocked main heat exchanger. Any of these have been found to cause problems, but have never had to change a plate!

You are probably a victim of a look'n'book by a lazy engineer! I bet it won,t be him coming back.

Well he did a good look at the temperature differences and then checked it with a mate on the phone before confirming that as his diagnosis; so it's at least two of them who are mistaken, and there are at least a zillion people on the web who've had the same problem and ended up replacing the plate.

Dave

Really! Let me know now it goes.
 
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I doubt it will be a blocked plate heat exchanger, more likely to be either of the pumps, mini PCB, main PCB, loom, blocked hoses, blocked canoe filter or even blocked main heat exchanger. Any of these have been found to cause problems, but have never had to change a plate!

You are probably a victim of a look'n'book by a lazy engineer! I bet it won,t be him coming back.

Well he did a good look at the temperature differences and then checked it with a mate on the phone before confirming that as his diagnosis; so it's at least two of them who are mistaken, and there are at least a zillion people on the web who've had the same problem and ended up replacing the plate.

Dave

Really! Let me know now it goes.

Ok! You get a cookie!

Another guy arrived on Monday and replaced the heat exchanger, found the temperature differential was still surprisingly high, and started looking again.

He said we had the *wrong* pump fitted (5m head rather than 7m) - which to me seems rather bizarre; but about a year after we had the boiler fitted the pump failed catastrophically and was replaced (by one of their guys), so it looks like they fitted the wrong replacement back then.
 
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