Pre-Heated water into a Vaillant ThermoMAX 824e

[championc]

Hi all,

I am planning to get an Evacuated Solar Tubes system for my house. If water from the solar store is Less that 40 deg, I plan to connect this to the Feed of the Vaillant Combi. However, I believe the 824e can only take pre-heated water up to 25 deg C.

Question
1. What happens if this Pre-Heated water was 30 deg C ?

2. Can anyone suggest a brand and model of Solar / Thermostatic Mixing Valve to compliment the Vaillant 824e ?


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[namsag]

According to the tech guys it can cause the plate heat exchangers to be damaged by getting too hot , said they split

 

[championc]

Is this because the modulating boiler can only go so low, and so, it will end up heating water 5 deg higher than it would normally do ?

If so, if I have my DHW set to run at 45 deg, then it would now run at 50 deg ? I think the DWH can go much higher than this - I have the dial set to about 12 O'Clock whereas the max is around to about 4 O'Clock (I think)


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[namsag]

Tech guy who spoke at installer live said because the boiler fires up on full gas straight away too much heat would go into it before stats would react to modulate it down quick enough.

 

[championc]

Do you or anyone know of a solar / thermostatic mixing valve which lowers to 25 deg C or lower


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[mickyg]

so you want to heat a load of water with a solar system then mix it down to 25C? isn't that a bit pointless?

 

[championc]

Hi Mickyg (and all others wondering the same)

If you install solar, after you use up the stored hot water, you'll then have access to cooler water which you certainly wouldn't shower or wash with.

Your mains water is probably going to be about 5 - 10 deg C. Therefore, if you're desired water temp is 40 deg C, you're Combi will have to heat this water some 30+ deg. However, if this water is 25 deg rather than 5, that's 20 deg less that your boiler needs gas for to raise the water temp to the desired level.

So it's all about maximizing the savings from Solar and using ever litre of warmed water, irrespective of how hot it has been heated.

Anyone with the model of mixing valve which will mix to 25 deg C or less ?


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[londonboy]

http://www.navitron.org.uk/product_detail.php?proID=360&catID=92

 

[championc]

Thanks Londonboy

However, it's spec says "Regulating temperature: 35-55°C" so surely this is no good to me ?

Vaillant say that the 824e ThermoMAX will only take a max of 25°C. Anyone any experience of this ?


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[ColJack]

could you not mix it at the taps?

hot water from the boiler and not so hot water from the solar, to limit it to say 50 at the tap?

 

[championc]

Solar water < 40°C is fed directly into the boiler to be heated up to 40°C. However, the boiler will explode (maybe not quite as dramatic as this but ....) if the water entering the boiler (to be re-heated) is > 25°C.

The simple answer is to have solar water until everything in excess of 40°C is used up and then just simply go with cold mains water feeding into the Combi - but this will eat up some of the residual benefits of the remaining solar heated water.


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[championc]

http://www.navitron.org.uk/product_detail.php?proID=360&catID=92

Quick question Londonboy

Can one of these do both the Anti-Scald and the Pre-Heat mixing functions or do you need two separate valves ?


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[Norcon]

It regulates the boiler supply to 28c and is factory set at this temperature.
http://www.intaeco.co.uk/resources/solar/intasol_installation.pdf

If your still on here then I suggest you contact the makers and see if they can modify this to your desired 25c. It may only need a cartridge change.
I'd use it anyway and take a chance at the 28c.

 

[londonboy]

Sorry for long delay, I didn't see the reply

I don't know any technical details for that, I have just seen engineers at work installing them