Flummoxed by Vaillant EcoTech Plus boiler

[Lucky Luke]

Hello, experts:

Our Vaillant EcoTech Plus boiler, with a part-central heating system, has been installed for three years, and we had it serviced this year, for the first time. Everything was said to be OK.

Recently, for the first time in all of the three years, I set the DHW to a higher temperature, as, in cold weather, it was not hot enough for a bath, and I had plucked up the courage to tinker with the settings (believe me, when I did this, I was terrified of upsetting the system in some way). When the engineer installed this boiler, he said that he was capping its capacity (how, I don’t know, of course), because there are only three radiators and DHW to serve, and there was no need for its full capacity to be enabled. Since then, when I leave a message for this engineer, I have found it impossible to get any reply from him. (I think that he must be more interested in installation jobs, than servicing work.) The man that serviced it this year was a newcomer. However...

I find that the DHW setting cannot be increased beyond 65° and, though this is better than it was, it still is not as hot as I would like it —not even after running it for a couple of minutes. Is there any way to increase the DHW beyond this point? Is the top limit of 65° a result of the deliberate reduction in capacity? I have looked in the manual, and I think that, if Comfort Mode were enabled, this might allow me to increase the DHW above 65°, but I am not sure. Also, the manual makes reference to a cylinder that, if Comfort Mode were enabled, would be kept at a fixed temperature (which cylinder, I take to be inside the boiler, since we have no cylinder for water anywhere on the premises). Reading the manual makes me dizzy!

However, even if there is a cylinder in the boiler (if there were, it would surprise me), there is mention of risk of Legionella bugs being encouraged.

In the manual, there also is a reference to VUI/VUW boilers. I have no idea whatsoever whether our boiler is either of these types, or another type altogether.

So, my questions, for anyone helpful enough to offer advice, are:

1) Can the DHW be set to a temperature higher than 65°, by any means whatever?

2) How can Comfort mode be enabled, and, in view of the risk of infections being harboured, would it be worth doing this?

3) Is this boiler one of the VII or VUW types, and what do these terms mean, anyway?

4) Would it be in any way detrimental to have the boiler set to its full capacity (i.e. as if there were a house-full of radiators)?

With thanks in advance, for helpful comments etc.,
A.W.

 

[simond]

Unfortunately, you have only told us you have a Vaillant ecoTEC. This narrows it down to around 30 models, some combi, some system, some open vent.

Your queries would have a different answer depending on which type you have.

It will either be a 4XX, a 6XX, an 8XX or a 937, 'x' being a number, usually printed inside the door or on a label at the bottom plate of the boiler.

If it is a 4XX or a 6XX it is unlikely that the hw control on the boiler has any function at all, other than in a 'Vaillant system solution', where you have a Vaillant branded thermostat/timer. You would know if you had one of these, because they are almost impossible to operate.

 

[Lucky Luke]

Simond: Thanks for your response. On the case of the boiler (at the bottom of the case-front), the words "Vaillant EchTech 824" appear. I did try looking underneath, and there are at least two labels there, with lots of details of one kind or another. However, with my bad back (at 82) and with my trifocal glasses, I could neither crouch to find a position from which to look, nor would have been able to get the focus if I had been able! Anyway, I hope that the number that I saw indicates what you would need to know.

 

[muggles]

You can't increase the hot water limit above 65°C in these boilers, nor should you. If it's not getting to 65°C currently, turning it up higher isn't going to make the slightest difference. It sounds like the flow rate through the boiler is too high to heat the water sufficiently, so reduce the flow rate out of your tap and it'll get hotter. Your incoming main is probably around 8°C at the moment, the boiler will heat water by 42°C at a flow rate of 8 litres per minute, so you'll only get water at 50ºC currently with an 8l/min flow rate. If you have a two litre measuring jug, try to slow the water down coming out of the tap until it takes 15 seconds to fill the jug. See how hot the water gets with this flow rate. If it's about 50ºc then the boiler is working as advertised.

 

[Lucky Luke]

You can't increase the hot water limit above 65°C in these boilers, nor should you. If it's not getting to 65°C currently, turning it up higher isn't going to make the slightest difference. It sounds like the flow rate through the boiler is too high to heat the water sufficiently, so reduce the flow rate out of your tap and it'll get hotter. Your incoming main is probably around 8°C at the moment, the boiler will heat water by 42°C at a flow rate of 8 litres per minute, so you'll only get water at 50ºC currently with an 8l/min flow rate. If you have a two litre measuring jug, try to slow the water down coming out of the tap until it takes 15 seconds to fill the jug. See how hot the water gets with this flow rate. If it's about 50ºc then the boiler is working as advertised.

Well, this would make things better, I'm sure, and I will try this, when I find out how to do it (as I said earlier, I am terrified of messing with the settings). If you (or anyone else) is able to answer my other questions also, I should be grateful.
A.W.

 

[muggles]

Comfort mode is enabled when the hot water is set to maximum. You should have a C on your display to show that it's turned on. It won't cause bacteria to build up, but will use a bit more gas. VUI/VU/VUW etc is just a Vaillant internal model code and not something you need to be concerned with. Setting your boiler to max capacity will most likely use more gas without any benefit

 

[Lucky Luke]

Comfort mode is enabled when the hot water is set to maximum. You should have a C on your display to show that it's turned on. It won't cause bacteria to build up, but will use a bit more gas. VUI/VU/VUW etc is just a Vaillant internal model code and not something you need to be concerned with. Setting your boiler to max capacity will most likely use more gas without any benefit

Thanks, very much, for those answers. Those questions have bothered me for a long time. Also, because I'm an inquisitive so-and-so, problem or not, what about the cylinder I mentioned? Is there one inside the boiler? (I'm a bit stupid, see?)

 

[simond]

There's no cylinder, just a set of metal plates with some water squished between them - this is part that is kept warm when the boiler is in Comfort (C) mode. No more than a litre in the boiler I'd guess, probably less.

 

[Agile]

You should really turn the hot water back to 55 C as that is more than adequate and any higher has a risk of scalding.

That's most important for older people because their response to over hot water is slower.

Your boiler is only capable of heating about 7-8 litres per minute of hot water.

Not opening the hot tap so much so the flow rate is reduced will give you hotter water!

Tony

 

[St0rmer66]

As above, turning the temperature on the boiler any higher than 55 or so will just result in you scalding yourself at low flow rates. The boiler can only heat the water so fast (24kw model you have is the lowest power output one they do).

The reduced output your installer was talking about was on the heating side ONLY. It has no effect on the hot water.

 

[Lucky Luke]

You should really turn the hot water back to 55 C as that is more than adequate and any higher has a risk of scalding.

That's most important for older people because their response to over hot water is slower.

Your boiler is only capable of heating about 7-8 litres per minute of hot water.

Not opening the hot tap so much so the flow rate is reduced will give you hotter water!

Tony

Thanks for this important information, Tony/Agile (also St0rmer66. who made similar remarks). I certainly will reduce the temperature!
A.W.