Heating system in new build house

[newhousenoclue]

I have just moved into a new house and was wondering if someone could please explain my heating system to me. We have a Vaillant ecoTEC plus 637 condensing boiler sitting next to a MegaFlo HE cylinder. There is a honeywell ST6400C display on the wall and then two fused switches next to that. The power for the MegaFlo Cylinder is turned off and I have set the Vaillant system to hot water on demand. The honeywell control panel is set to off for the hot water and heating. I have a few basic questions:

1) What is the MegaFlo system for when I have a boiler next to it?
2) Why is the power off to the MegaFlo
3) Does the Honeywell controller (and thermostat downstairs) override the control panel of the boiler?
4) Should I pay £89 to Vaillant to upgrade my warranty to a 3rd year?

Thanks so much for any help.

 

[kevplumb]

1) What is the MegaFlo system for when I have a boiler next to it?

stored hot water

2) Why is the power off to the MegaFlo

that will be the immersion heater supply

3) Does the Honeywell controller (and thermostat downstairs) override the control panel of the boiler?

wouldnt think so

4) Should I pay £89 to Vaillant to upgrade my warranty to a 3rd year?

certainly wont do any harm

 

[ChrisR]

The 637 is just a boiler. It doesn't heat tap water inside it like an 837 combi would have.
It probably has a water temperature knob on it, which does absolutely nothing. They make more combis, so they just take bits out and sell it as a plain boiler.