MegaFlow Heating sensor and the Valliant VR10 sensor

10 Sep 2012
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United Kingdom
Folks good morning,

Hopefully an easy question. I have a Valliant Ecotec 637 and a megaflow tank. I am having real issues with the installers with the wiring of the boiler and tank. The megaflow has its own built in temperature sensor. The boiler has the VR10 temperature sensor. speaking to valliant they said i need to use the VR10 sensor - but with the megaflow and its metal lined tank there is no jacket pocket for the sensor. surely it would be better to use ONLY the megaflow built in temperature sensor?

Thanks for taking the time to read...
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Is this a real Megaflow with that name on it?

If so it only has a thermostat and not a temperature sensor!

It can still be used with your boiler but only with on/off stat control.

Your installers dont seem very clued up!

If the cylinder stat on the megaflow is the immersion type in a pocket then remove that and slip the vr10 in in place..that leaves the over heat stat vial next to the vr10
Thanks Tony/Alec1...

Yes the is the tank is:

Heatrae Sadia Megaflo Eco 210Si Indirect Unvented Hot Water Twin Coil Solar Cylinder - 210 Litres

I had a look at the online manual and yes Tony it has a Thermostat. So i guess i set the water temp on the megaflow? The boiler would only heat the water to this temperature - would that be correct? If so what happens to the settings on the Ecotech 637 for hot water temperature is this then ignored?

In such a setup should i still be looking to get the installers to just use the Megaflow thermostat - and not bother with the VR10 sensor?

And yes agreed my installers are not clued up. I have discovered this the hard way. It has cost me money and almost my marriage!
They have wired up my dual zone incorrectly and my hot water only works when the heating is on. Disaster.

I may end up looking for a local installer to re-wire the whole thing.
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you loose two things using an on-off thermostat connected to the VR65 instead of vaillant's VR10 sensor

1) Precision temperature setting on the controller (VR 470 and 350) of the use of the hot water knob on the boiler to set the DHW temperature

2)Enhanced boiler performance... with the VR10 the burner monitors the draw off and determines its reheat rate as opposed with the on-0ff control it just fires to maximum in an uncontrolled fashion...the benefits are a moot point, but the technology has evolved for a reason...

3) You loose the use of the legionella programme with an 0n-off thermostat...

4) You loose cylinder boost with on-off thermostats...

To some using an On-Off thermostat with vaillant's excellent technology is a bit like buying a fast computer and using a telephone line for the internet connections.
Excellent post Alec1. I would want to use the VR10 Sensor - From what you said i'd be crazy not to.

I've spoken to megaflow who advise me to get a 1/2" BSP SENSOR POCKET ASSY (p/n 95607938). they have also stated the Megaflow Thermostat must be connected to meet building regs as it is a pressurised unit.

I will point all of this out to the installer... and keep my fingers crossed.

To some using an On-Off thermostat with vaillant's excellent technology is a bit like buying a fast computer and using a telephone line for the internet connections.

Sometimes people get a little over excited without putting things into perspective.

Heating hot water only accounts for 5-15% of the average gas bill. So as a proportion of the total annual gas bill a little inefficiency on water heating becomes rather insignificant.

There is another aspect often forgotten. When using clever controls for heating cylinders the boiler tends to be modulated back to improve efficiency but this can reduce the power output and take longer for the reheating.

To me thats not very relevant but still it seems very important to some people to reheat quickly. When the cylinder is being heated then the rads ( on that setup ) are off so a slightly longer time without heating!
brilliant picasso...

Tony of course the coil should be correctly sized so that if there is a big draw off detected by the sensor the cylinder can recover quickly...

to me its about fit for purpose and being coherent to design principals of the boiler...

I tend to think that the manufacturers design engineers know what they are doing...

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