I need help with my Mega Flo: no hot water

[Bmidreams]

Hi, I've just moved in to a new house. It has a vaillant combi boiler and a megaflo hot water tank. We've been here a week and now the water is going cold. Does this mean the hot water is not coming from the boiler? Do we need to switch the hot water button on the megaflo on? Or is this switch just a top up? Can I switch this switch on when the boiler is running too? Have we no hot water as we have simply drained the tank, or is something broken? I've never had this system before. Many thanks. I'll tag @pigletjohn too!!!

Are you absolutely sure it's a combi boiler?

No I'm not.

Dh has put the hot water switch on now.

Have you got the instructions? You should be able to download them from the Vaillant website if not.

Or the Heatrae website for the Megaflo

I think we need to know generally where our hot water comes from before we can look at instructions. I've googled but it's hard to know what's what

the switch is most likely for an electric immersion heater, which is slower and more expensive than the gas boiler. Does it have a thick flexible cable? Where does it go?

It might be the timer settings on your boiler programmer. Please post photos of that, and all the buttons, switches and displays on the boiler.

Are the radiators hot?

Hot water coming in but not goimg into tank, but dh has switched to manual and now it is. Tank is cold.

We dont have hive subscription.

The only boiler controls are in my first picture.

Since we moved in last week we have 3 radiators not working.

So when you push the switch on the silver box from auto to manual on the left does that make the water heat?

Not yet. But the out pipe was cold and now hot.

I think it's something to do with your controls.

the "silver box set to manual" is the motorised valve that should be opened by the timer and the thermostat on your cylinder.

As you've recently moved in their might be some setting that is "off"

I can't see what it is.

Might be the Hive.

I can't see what temperature the knob on the boiler is set to.

If you can speak to the previous residents, they may know how to set it.

If you don't get any good ideas on here, call a recommended heating engineer to puzzle it out. It's possible (though I think less likely) that there is an actual fault.

A large unvented cylinder like your runs the boiler more economically if it is fully heated morning and evening, rather than left on all day; but in winter, when the boiler is running all day for the radiators, it won't matter.

Setting the valve to "manual on" can cause the water in the cylinder to become scalding hot, so take care. If you can adjust the boiler temperature to 60C or thereabouts, the cylinder will not get hotter than that.

Thank you so much for taking the time to reply. We bow have scalding hot water.

If it works when set to manual but when on auto it isn't switching properly, then I think it could be that the valve needs replacing which is fairly quick job for a central heating engineer.

Thanks. I think dh said it's £25 from Screwfix.

though I think it is more likely an error in the controls.

those motorised valves commonly last around 20 years.

I'm definitely no expert I just mentioned it because it happened to us recently and valve needed replacing though it was the heating valve rather than hot water.

Think it might be the motor in the valve. The house is 20 years old! Thank you!