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Discuss Megaflo only heating with immersion? in the Central Heating Forum area at PlumbersForums.net

MarkLucas

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Hey everyone,
We bought this house and don't know much about plumbing, and we haven't received any information from the previous owners as to how the central heating was set up.
It's a 4000 sqft house, which is heated with a combination of underfloor heating in the ground floor, and radiators on the top floor.
We have a Vaillant Ecotec Plus 637 boiler and a Megaflo Indirect of 300L capacity.
We had smart meters fitted this week and I noticed that the electricity usage has some spikes of 3000W for about 5 minutes, and it keeps doing it all day long. Upon investigation, I found out that's the Megaflo.
Since I have an Indirect Megaflo, I presume it must be connected to the boiler as well. However, since the boiler is not being used since the heating is off for the house, I imagine the Megaflo must be heating only with electricity.

My question is: If the heating is on, can I presume that the Megaflo will be getting some of the heat from the boiler?
There are 3 switches next to the Megaflo which I couldn't exactly find out what they did. One of them seems to turn off the Megaflo as a whole, another one is connected to a timer, which is then connected to a DAB Pump connected to the Megaflo, and the last one I have no idea because it goes inside the wall.
I tested turning on the hot water using my thermostat and nothing seems to happen. The boiler doesn't have the icon for hot water, only for heating.
I attached some pictures, that I hope will help to understand.

Any information I can have would be greatly appreciated.

Thank you from a very concerned new homeowner :)

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Gasmk1

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only if the timer is calling for hot water if it is then the silver box on the pipe feeding the magaflo should be open if the lever on th evalve is loose then it is open and should be calling for the boiler to be on if it is still stiff then its faulty, you may be able to sort this yourself with some searching. but i would advise you to calll a good heating engineers who is gas safe and G3 should be a fairly simple fix
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you also have a nest thermostat fitted is this working properly
 
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MarkLucas

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Thank you for your reply, I guess I don't know which lever to check.
The Nest Thermostat is working properly (I have 3 actually), but one of them has the option to turn on hot water, which I don't think does anything.
I think I might have to call a heating engineer, but in my experience they usually charge a lot or they just look at the system and say it's too complicated... I was hoping I could figure it out myself
 

snowhead

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That should be trying to drive the valve open on the Megaflo.
The one mentioned in post #2 , with the black triangle and H/W on it. Above the grey box on the Megaflo.
 
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MarkLucas

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That makes sense, I can't really tell if that valve is working or not.
In any case, I'm trying to decide if it's worth paying for the engineer to come and fix it, how much should I expect it to cost if the problem is only that valve or maybe "user error"?
I'm in Hertfordshire

Thanks
 
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Without stating the obvious, I know the NEST is meant to control the HW but have you tried turning on the HW to 'on' (So the green light comes on) on the White Honeywell Timeclock on the wall to the right of the cylinder?
 

chris watkins

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Mark
Turn the FCU (neon switch) underneath the pump switch off this is the power supply to the immersion & is only used as a back up if the boiler fails , this is why you are using a lot of power.

Push the left hand button on the programer (HW) so the the box moves over the Auto or On's for hot water. Make sure the boiler set temperature is at least 70 deg C.

Timer is controlling a secondary circulation pump (which is leaking).
 
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MarkLucas

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Mark
Turn the FCU (neon switch) underneath the pump switch off this is the power supply to the immersion & is only used as a back up if the boiler fails , this is why you are using a lot of power.

Push the left hand button on the programer (HW) so the the box moves over the Auto or On's for hot water. Make sure the boiler set temperature is at least 70 deg C.

Timer is controlling a secondary circulation pump (which is leaking).
Thanks, I tested that and the Programmer doesn't turn on the boiler when On, so I guess there's a fault there.
I contacted a heating engineer in my area to have a look.

Thank you so much for the help
 

Chuck

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I contacted a heating engineer in my area to have a look.
Don't use the electric immersion heater to heat the Megaflo unless your boiler is broken. Gas is cheaper by a factor of about five times than leccy and the reheat time with gas will be 10% of the time a 3kW heater will need.

For many families, having the hot water programmer set to come on for an hour or two between 0500 and 0700 works pretty well. 300 litre is enough for five 'British Standard' baths filled with 100 litre of water at 40°C.
 
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MarkLucas

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A heating engineer was here and diagnosed that indeed that valve is faulty.
He quoted me £200 to supply and fit it.
Does that sound about right?
Thank you very much
 

gpbeck

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Well he’s making 2 visits. Gas cost is perhaps a quarter of electricity on standard tariffs but the complexities have other costs! Nobody bothers with insurance cover for immersion heaters.
 

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