Newly installed Combi/Megaflo and Immersion heaters

8 Mar 2019
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United Kingdom
I need some help!
I have recently had a small extension to our 3 bed semi and with the work they have moved our boiler from the kitchen to the loft and as the water pressure upstairs was too low have installed a megaflop as well.
I connected our smart metre earlier in the week and we are draining energy - averaging £8-£10 a day!!! The megaflo has two immersion heaters connected to it, not on a timer, but constantly on and there is a thermostat set at around 45 degrees.

Does the boiler heat the water in the megaflop or does the immersion?

Any ideas?
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1. Whether or not the boiler heats the cylinder depends how its been installed.
2. Easy way to find out is to switch off both immersion heaters and see if the water goes cold (could easily take 24 hours).
3. A thermostat at 45 degrees is far too cold if it sets the hot water temperature. Needs to be around 60 degrees to avoid legionella from stored water.
4. Pictures of installation around cylinder might help.
Thans for the reply.

1. I turned the immersions off a Cpl of days ago and they went cold last night.
2. as above
3. Thank you. I was hoping to lower it to reduce the cost. I'll increase to 60 degrees
The Boiler should heat the water in the megaflop, gas heating is far cheaper than electric! Immersions should be kept for backup if gas heating is available.

Without seeing the setup it's impossible to say exactly what is happening (or not happening), but my first port of call would be to see what the heating controls are set to. If the HW side is switched off, then the boiler will not be heating the water. We really need more details of the system please, which will help point you in the right direction of what to look at.
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What model is the Megaflo? If it is direct, it will be immersion only. If it is indirect, it will have a coil running through it with flow and return pipe connections to be heated from the boiler - some pics here would easily identify it.

Indirect cylinders have an immersion heater too - but this is used only as a backup.










Thanks for your responses. See photos below

Note the n/a on the boiler is when I turn the dial for hot water

So, we as a family have been out from 9am to 5pm today and we have used :

Electric £4.93 - 31 kWh
Gas £1.61 - 42.56 kWh - been unchanged since 9am
Last edited by a moderator:
It's an indirect cylinder and the boiler flow is to the left of the bottom immersion and the return to the right of the bottom immersion.
turn the immersion heaters off they are only for emergency back up
Ok. Why do you think it says n/a on the boiler when I try to adjust the hot water dial? Any way I can change this?
The boiler doesn’t seem to come on at all when you turn the thermostat on on the megaflo. Just doesn’t seem to be connected
The original copper pipework looks neat.

Did your problems start after the plumber sent his granny to add those plastic pipes? What do you know about granny's qualifications?
Thanks for above. Not overly helpful. The plumbing company are back on Monday so will discuss then

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