Switching / wiring advice for Megaflow with 4x 3kw immersions?

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64sp said:
Hi

I have bought a Megaflow 210dddd which is a direct model (electric heating only) with 4x 3kw immersion elements. It’s providing hot water to 2 showers in a swimming pool changing room and so I went with the 4 immersions so that I could get quick re-heat times when the showers are being hammered by the kids!

The electrician is coming next week to put the wiring in before the plumbers commission it. I could therefore do with some advice and thoughts about possible/best ways to switch the immersions so that I can have a more educated conversation with my electrician about what I want to achieve. In the past (other houses) I have only had either a single immersion (20amp DP switch to turn on and off) or in one case a top and bottom immersion with one of those bath/shower DP switches to choose between bottom OR top.

The consumer unit is close to the water tank and so it will be easy enough for the electrician to run whatever he needs to provide the initial supply (assume it will be a big old cable given the potential for 12kw / 52amps being pulled). I’ll leave that to him.

What I am interested in is whether anyone has experience of these 4 immersion versions and what switching options they have installed. The layout seems to be 1 immersion at the bottom, 2 either side of that slightly higher up the tank and then the 4th about half way up the tank. I’m not clear on what that layout says in terms of which ones should be used on their own or together.

I do want the potential to have all 4 on at the same time for maximum speed heat up, but equally want to be able to have 1 or 2 on when speed isn’t an issue and/or I just want some hot water for the sinks.

Any thoughts on how best to setup the switching?

Presumably one option is to have 4x 20amp DP switches and just switch each one separately in whatever combination I want (or all together) but should I have a more sophisticated method?

Any thoughts gratefully received!

Thanks
Click to expand...
Hi 64sp, I am sure this forum is leaving you more confused than when you started.
The illustrious members of this forum with to many answers have a strong Domestic installations bias.
You will need a Commercial electrician to do your job not a Domestic one or one who is experienced in both fields but in general electricians tend to stick to one field.
So trust your electrician and ask for his credentials as many will claim they can do the job so they can get in and claim the money.
 
Last edited:
SPECIAL LOCATION said:
Really? Two separate circuits to one unit..
e.g one double gang switch having TWO sources of power?

Regulation please may help?
Click to expand...
Regulations are a guidance not laws, in the Regs themselves it's stated use common sense.
Like I said above which I hope you read and if you have done any testing and inspection one of the things to note on your certificate if there's a dual supply you need to have to put a yellow sticker of warning but of course you wouldn't do this on a domestic install.
A light switch and a boiler is exactly that comparing apples with pears.
And I have no more to add to this thread because we have different electrical backgrounds, although in theory we should reach the same conclusions we are obviously not.
 
64sp said:
I think there is only 1 spare way in the CU. I was so focussed on how I would like the switching to work I hadn’t thought through how the electrician will get the power to the immersions. I guess I assumed a large amp breaker and a big cable that would daisy chain / split into the switches - but totally makes sense why you say 4 radials.
Click to expand...
I would set that up with 4 timers so that it's not running the immersions all the time, 24/7. Bottom immersion is your main unit, ideally that one would be on an off peak tariff. Top immersion probably won't do much for you, that would be just a booster for an individual bath should the tank be drawn down. Probably not even worth connecting? The 2 middle units would provide the extra boost for periods of high demand, so set those to run when you think high demands will occur. Modern tanks are very well insulated, which helps a lot, once heated they stay hot for over a day from what I've seen. I would also consider changing the shower heads for ones which mix air into the water and reduce the amount of water used - sounds like that could save you a small fortune.
 
dont let him see those night storage heaters that require 2 different supplies, both on peak & off peak. he'll be calling the electric police about those
 
I would be looking at Roof panels to help with the running costs and keep the installation simple with four radials
and off peak so the bulk of power at night unless you have very deep pockets.
 
Generalising, it will always take the same amount of electricity to heat up a completely cold tank
Whether only one, or all four elements, are in use.
The number of elements in use will determine how quickly the water is warmed.
So there are many possible combinations of cylinder stats and elements stats, and I'll leave that to the experts.
But I believe the experts say that the best economy is to try and keep the well-insulated tank full of hot water.
 
Seriously. The big tank and a big heater is going to cost a fortune and standing heat losses when not in use, will add to the cost.

Put ONE instant electric shower and make them take turns. It will only use the electricity it actually needs to provide the shower.
 
Please excuse me for diverging from the original question.
Myself and Mrs sometimes stay in Premier Inns, which appear to be all electric. (I'm not saying they all are but definitely visited several). These hotels seem to be capable of providing everyone with morning showers or baths, probably all within a couple of hours, and without fail.
How are they equipped to do this? Anyone know?
 
Geoff1946 said:
Please excuse me for diverging from the original question.
Myself and Mrs sometimes stay in Premier Inns, which appear to be all electric. (I'm not saying they all are but definitely visited several). These hotels seem to be capable of providing everyone with morning showers or baths, probably all within a couple of hours, and without fail.
How are they equipped to do this? Anyone know?
Click to expand...
I think they use something similar to a "Belfast" immersion , the proper name escapes me, that's the colloquial term we used, it's a small tank attached to the main cylinder with the immersion heater element in it, so it basically heats the water as it's drawn out.
In a normal domestic it slows flow down a bit , but obviously larger versions would be used in commercial.

That could all be total bollicks tho, I know very little of such things
 
steptoe said:
That could all be total bollicks tho, I know very little of such things
Click to expand...
indeed it could. As has been stated on here frequently MOST of us know very very little compared to a select ( self appointed ) few. Just look at the utter S.H.Y.T.E. that has been posted on various threads here recently. People stating how great they are but asking the most puerile questions. Stating stuff CANNOT be done but when asked to quote a Reg run off crying to nanny! Anyway, rant over. I thought it was me that "knew little of these things"! It must be contagious 😂😂😂🤡
 
kerching said:
indeed it could. As has been stated on here frequently MOST of us know very very little compared to a select ( self appointed ) few. Just look at the utter S.H.Y.T.E. that has been posted on various threads here recently. People stating how great they are but asking the most puerile questions. Stating stuff CANNOT be done but when asked to quote a Reg run off crying to nanny! Anyway, rant over. I thought it was me that "knew little of these things"! It must be contagious 😂😂😂🤡
Click to expand...
the recent sunshine hasn't made you any happier then? :ROFLMAO:
:ROFLMAO:
 
Thanks Steptoe. Your comment, plus a bit of Google has led me to a "Willis" heater, which broadly fits your description.
I'm still struggling to understand the thermo-dynamics of this but it's probably part of the answer.
I think it looks like having a stored hot water supply boosted by an instantaneous heater, but is that it ???
 
binky said:
the recent sunshine hasn't made you any happier then? :ROFLMAO:
:ROFLMAO:
Click to expand...
Oh how WRONG you are! You should have seen me when the weather was miserable! My fluffy cuddly kitten like persona was almost approaching terse and, how can I put it?, I was becoming a little grumpy! I know it's hard to believe
 
Geoff1946 said:
Thanks Steptoe. Your comment, plus a bit of Google has led me to a "Willis" heater, which broadly fits your description.
I'm still struggling to understand the thermo-dynamics of this but it's probably part of the answer.
I think it looks like having a stored hot water supply boosted by an instantaneous heater, but is that it ???
Click to expand...
That's it,
Willis heater ,
It's not actually an instantaneous heater , it's a side effect of on immersion that's not actually in the tank, but that may solve the issue.
 

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