Vaillant Turbomax 828e CH turning on ignoring the timer

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Hope someone can help, I've noticed in the last month or so that my Vaillant Turbomax plus 828e is ignoring the settings of the timer - Switch110 - it seems to be following the timer during the day, but turns the CH on randomly during the night when the tappets on the timer switch are definitely set for CH to be off (from around 23:00 - 07:00).

I've checked the basics, like the time that the programmer is set to and it's correct. Have rotated the time through 24 hours to listen for the click as the tappets cause the switch to request the boiler to demand CH. This all appears fine, as the Switch 110 is just a mechanical / clockwork timer, it Appears to be working correctly.

Note that this is my second Switch 110, first one installed with the system stopped going round, just died stuck at one time and was replaced under warranty.

As the CH comes on independent of the timer in the middle of the night, and appears to work OK during the day, I'm wondering if it has something to do with the frost thermostat (but this is pure guess and probably wrong!).

The hot water demand is fine and the CH operates correctly when the timer requests that CH be turned on. There are no fault codes displayed on the status panel. If I check when the system turns itself on randomly, status d 8 = 1

Boiler is 2 and a half years old, I live in a hard water area, boiler has been regularly serviced since install.

Has anyone got any ideas, or seen this before?

Many thanks
 
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Are you sure it's not 'comfort heating' the hot water? (ie. pre-heating the boiler and contents so hot water arrives quicker when you turn on a tap)
 
Hi croyoncorgi

thanks for the reply and suggestion, but it's not the aqua comfort feature, I've verified that it's switched off.

It seems to also do it a bit randomly during the day, I find the radiators are warm, go and check the boiler and find that the burner is lit and the CH pump is pumping water around the circuit, but the timer has the tappets out so that the CH circuit shouldn't be coming on. It seems to think that it should be on even though the schedule on the timer says it shouldn't be on until a few hours later.

If I turn the CH off on the main switch on the timer, then the boiler doesn't start up, as you'd expect it to, with the switch off hot water is still fine.

So it looks like the timer is faulty, but something to do with the electronics as the rest is just clockwork / mechanical.

Maybe the frost sensor could be faulty. Perhaps the sensor only operates when the CH is switched on via timer as you'd not need it at all in summer and had turned the CH off on the timer??
 
I've just been watching the boiler start itself up even though it's set to run on timer and the timer says that it's not to be on just yet.

The boiler has very useful status and diagnostic controls, what appears to happen is that the boiler waits until it's counted the anti cycling minutes down to 0 then it starts up.

It then runs until the correct temp is reached in the return and shuts down, it now waits until the anti cycling timer gets back down to 0 and starts up again. So it seems to think that it should be on even with timer tappets out so that it's supposed to be off.

The factory default appears to be 15 minutes for anti cycling (d 02 = 15), but it seems from d 67 that anti cycling starts counting down from 5, am I missing something, shouldn't that be 15 or is d 02 only the max anti cycling time ?

Anyway the status it is showing just after shutting down is s 8 anti cycling, then it starts up again when d 67 gets to 0.
 
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You don't say what status code is displayed when the boiler is firing without call. You say that before this it shows S.08 which is the anti-cycling mode, but what after that?

On the diagnostic codes, you say it shows d.08 = 1, which means that the controls are calling for heat. Are you absolutely sure that they're not doing this?
 
Hi Chrishutt

Thanks for the reply, well spotted, I also looked at d.08 and saw that it was calling for heat demand, but the timer clearly is not calling for heating, that's what is confusing me.

As soon as the anti cycling period ends, the display goes through S.02, S.03 S.04 it then runs until the return temp is reached and then shuts down going into S.07 and then S.08 again.

I can't understand why (unless the electronics on the timer control are faulty) the system thinks there is a demand for heating.

Is there anything else that could cause the system to override the timer (this is why I thought of the frost protection)? Haven't ever seen S.34 though as the house is pretty warm, if the water supply gets down to 5 degrees or so would this cause the frost protection to engage ?

All thoughts welcome
 
You've clearly got a call for heat. Do you have any external controls - room stat or frost stat, etc.? Can you check that they're wired up to the boiler properly?

built-in frost protection or HW preheat would show up with different status codes, so we can rule them out. However an external frost stat would overide the timer and appear as a call for heat.
 
Hi Chrishutt

No external controls other than the timer itself. I was just watching it start itself up again, waited until I saw the anti cycling time at 1 min, then switched back to status to see what it did, went from S.08, displayed S.00 for a split second then S.02 S.03 S.04 again after the 1 min was up.

I think you're spot on, there is a demand for heat, once it started up, I went and checked d.08 and it was 1, the thing I can't understand is where it's getting the demand from.

I've taken the old Switch 110 apart to see what it looks like inside and it's really simple, clock rotates and the tappets if they're pushed in, cause a small plastic lever to press a switch to create a heat demand circuit.

There's really not much that can go wrong there, so I'm guessing that it's the circuitry that's at fault?

Looking at some of the other posts here, it seems that I can look forward to replacing the diverter value anytime now and the APS at the same time?
 
hey smashman

I've got turboMax 828E also. I've had mine in for approx 3 yrs now + recently it started to run the CH itself. Then after a few mths, when the CH was on i couldn't get HW- to get HW i had to reset the boiler to switch off the CH. Another 1/2 mths later i couldn't get the CH off by resetting the boiler, so i went thru a few weeks without CH in order to get HW when we needed it.

I then had to change the diverter valve + everything has been ok so far ;)

The diverter valve on these boilers stick in a position, therefore when i had the CH on i had to reset the boiler (+ therefore the diverter valve switch) to switch it back off. Eventually the valve sticks in the CH position & the only way round it is to replace.

I spoke th Vaillant + said 'your diverters are notorious aren't they?' + they replied with 'to our knowledge we have not got a problem with our diverter valve's' wtf?

Anyway my plumber has said he replaces them constantly on these boilers. I'd say give it a while but start looking around for the valve. My plumber's merchants wanted £130 ish for it, i ended up getting from ezypart.co.uk for approx £85ish i think. My plumber charged me £30 to fit it..... 10 min job
 
Thanks pica27

It's a pity everything is made disposable these days, lasts five minutes and then gets chucked in a land fill somewhere.

I wish someone made boilers like they made the old Routemaster busses, the over-engeneering that went into the window winders was exceptional, but they never broke and never had to be replaced.

Thanks for the advanced warning.
 
In case this helps someone with a similar problem some time in the future.
I ordered a Swithc 120 (Digital 7 day timer) and replaced the Switch 110 (clockwork timer) and the problem appears to be solved.

So it appears that even though the mechanics of the Switch 110 were fine, the electronic were not, it appears a faulty Switch 110 was creating heating demand and the boiler did what it was asked to do.

Note that the faulty Switch 110 was the second one, first was replaced under waranty when the clock just stopped running a few months after installation.

We'll see how long the Switch 120 lasts.
 
Thanks for the feedback. It helps us to know the answers to these puzzling ones.
 
yep cheers smashman

Interesting that your problem was the digital timer, u ever thought about getting a mechanical clock?.......i've got one + it's been:cool:

At least your diverter valve is ok anyway
 
I am amused that when he called Vaillant they replied that "to their knowledge there is no problem with the diverter valve".

Really, what LIES !!!!!!! These guys are giving out these lies every day otherwise they would get the sack!!! Its a pity that they do not have more honesty and dont want to tell the truth.

Clearly they are happy being paid to tell lies!
 
Hi

Well I had a 120 Digital Switch which never came on, and I inherited our boiler about 6 years ago (Turbomax Plus).

I replaced it with a 110 mechanical switch, which was bringing the CH on whenever it wanted to. Tappets set to off. So much like this problem but the digital 120 switch wouldn't bring it on. I suspect the problems we have experienced aren't with the switch but the boiler itself.

If anyone has anything to add or recommend I'd be glad of the advice before I call a plumber in.

Stu
 

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