Cheapest way to run immersion heater

Swipe

wittynamegoeshere said:

Swipe said:

I really don't understand the obsession with legionella bacteria on this forum, it is absolutely laughable. How many people do you actually know who have had legionaries disease, let alone caught it from water standing in a pipe for 24 hours? 

Also the small amount of chlorine that's added to the water supply to keep it fresh has the opportunity to evaporate off as gas into the air.

Most water companies have replaced chlorine with chloromine which does not evaporate.

wittynamegoeshere

Thanks, I didn't know that.  That's bad news for fishkeepers then, I had them as a kid, far too many years ago.  I used to fill my fish tanks and just leave them for 24 hours for it to evaporate.  It's all much more involved now...

https://www.thesprucepets.com/remove-chloramines-from-tap-water-2924183

I wonder if heating it removes it though?  Can the bugs come diving in once it's got hot and gone cold again?

Section62

wittynamegoeshere said:

It's pretty simple, flowing = fresh, standing = stale.  Just like a river vs a pond really.

That's overly simplistic.  The "flowing" river water could be full of CSO discharge and the "standing" pond completely wholesome.  We have something of an innate fear of "standing water", it probably starts when parents told us not to play in muddy puddles.  But that isn't really applicable to potable water supplies.  Perhaps you don't realise that your 'fresh' tap water has probably stood for some hours (possibly days) in the water supply network?

wittynamegoeshere said:

As far as I know, the legionella risk only applies to standing water.  You're scaremongering here by suggesting there's a risk that simply doesn't exist.

You'd be wrong in that belief.  Which is why there's a risk to be considered in water system design - it isn't 'scaremongering'. Please, if you are going to offer advice on this topic, check your facts first.

wittynamegoeshere said:

Sorry if you disagree, don't like my opinion or attitude and if I don't fit your personal model of how everyone should be, but it all sounds like you're looking really hard to find things to take exception to for whatever reason.

None of the above.

I just feel it is important that a forum like this one is somewhere that people can get accurate information and not be misled into making a potentially expensive/unsafe mistake.  If people are giving inaccurate information they shouldn't be surprised if another poster politely points that out.

wittynamegoeshere said:

You're also equating a perfectly sensible and "money saving" way of heating water with a whole bunch of products and companies that are definitely all scams.  I have an engineering degree, I've had shouty arguments with Fischer employees in their stand at a country show, I do know that there have been many exciting new products that are complete rubbish that are marketed in immoral and deceiving ways.  But I think you're tarring everything with the same brush in suggesting that anything unusual or novel is always bad or a scam, which is a pretty negative approach.

I have an engineering degree too.  Plus I've put the degree to practical use working in public health and building services.

Now our respective qualifications are out of the way, I'm not "tarring everything with the same brush".  I'm pointing out that different things have advantages and disadvantages, and what is right for one situation may not be right in another.  The wonder heaters promoted by some sections of the industry are not 'bad' or "scams" per se.  They comply with regulations and are comparable in terms of electricity consumption to similarly rated products.  The problem is them being 'sold' to people using inaccurate/misleading information, so people end up with an appliance which is unsuitable for their needs.

My comments have nothing to do with instantaneous water heaters being "unusual or novel".  In fact I pointed out earlier in the thread that there is nothing new about them. I also explained that I've been involved in speccing them in projects I've been involved with.  Perhaps you missed that?

wittynamegoeshere said:

Besides, there's nothing new about heating flowing water.

As I said several pages ago.

wittynamegoeshere said:

But I've already given a whole heap of reasons why this may not suit everyone, I'm just throwing an idea in the pot to consider with a stack of disclaimers but seem to have wound up a few people.

Your earlier posts were categoric that hot water cylinders/immersion heaters were a thing of the past.  Specifically you said "The cheapest way to run an immersion heater is to not have one at all!  Get rid of the stupid tank altogether and get something like this".

That goes a lot further than "just throwing an idea in the pot to consider" - it was a categoric judgement on a system which works just fine for many thousands of people.  The claim also isn't based in fact.  The disclaimers - including that the model you have is useless for filling a bath - came much later in the discussion.  Though were welcome.

If you'd limited yourself to saying something more balanced - such as people should consider instantaneous water heating as an option - then I'm sure this thread wouldn't now be on its 7th page.

Section62

wittynamegoeshere said:

The warm water remaining in the pipe is pretty much the same situation as the pipe from a hot water cylinder.  Either way, it remains there, in theory festering.

No, there's a fundamental difference.  The water coming from the hot water cylinder should have been heated to at least 50C, preferably 60C.  This will kill legionella in the water.

Water from an instantaneous heater of the type under discussion never reaches this 'safe' temperature, so any legionella aren't killed.  Instead the water will be around the ideal temperature for bacterial growth.  Hence the advice to install instantaneous heaters as close as possible to the point of use - it minimises the volume of water kept in the 'danger' zone.

wittynamegoeshere said:

But so does the cold water, which may reach room temperature or above.

They are dormant below 20C.  Hence the basic plumbing philosophy of seeking to keep cold water cold, and hot water hot, and not in the 'danger' zone.

This is exactly the same as the basic approach to food safety - keep it cold, or heat it to 'piping hot'. The greatest danger is with uncooked food which has been kept in warm conditions.

wittynamegoeshere said:

I'm pretty sure there's a big difference between standing and flowing water.

No, there is no big difference.  What matters primarily is the length of time water has been in the temperature danger zone.

wittynamegoeshere said:

Electric showers heat to only a warm temperature then spray it into the air without any precautions, so presumably this is OK.

Because the input to an electric shower should be cold, and the volume of water after the heater is kept to a minimum.

moneysavinguser123

Sorry to necro a thread from years ago but this is relevant to me but I can't find the exact answer, and I'm worried as we're being saddled with huge electricity costs. I have just moved into an all-electric 2 bed flat with a Megaflo Heatrae Sadia 170DD. I'm completely new to this and don't quite understand how the two compartments (top and bottom) work.

We have a fixed rate electricity tariff (having read this thread we should've got an offpeak/Economy 7 tariff as the unit is designed to heat water cheaply at night...but we didn't know the boiler type when we chose the tariff, our first mistake). We have electric underfloor heating so the Megaflo is only used for hot water for one shower per day each. Apart from that we will be washing up and washing hands etc. in cold water almost all the time so low to neglibile hot water usage outside showers. Our Megaflo does not have a timer, and as far as I can tell has no switches/buttons for 'boost', only two switches on the wall to turn the Megaflo's two compartments off. What is the cheapest way for us to use the boiler for heating enough water for two showers per morning (10 min average length each). Would it be better to turn the top compartment or the bottom compartment off?

QrizB

moneysavinguser123 said:

I have just moved into an all-electric 2 bed flat with a Megaflo Heatrae Sadia 170DD.

...

What is the cheapest way for us to use the boiler for heating enough water for two showers per morning (10 min average length each). Would it be better to turn the top compartment or the bottom compartment off?

A typical electric shower runs at 5-10 litres per minute, so 50-100 litrs per shower. If half of that water is hot from the tank, that's 25-50 litres of hot water per shower; 50-100 total for two showers.

Your tank only holds 170 litres total, so heating the top half might not be enough for your two showers. The simplest way to know is to try it. I suggest you take the second shower so your other half doesn't complain if the hot water runs out half-way through  

moneysavinguser123 said:

We have a fixed rate electricity tariff (having read this thread we should've got an offpeak/Economy 7 tariff as the unit is designed to heat water cheaply at night...but we didn't know the boiler type when we chose the tariff, our first mistake).

If you want E7 instead, your supplier should be able to swap you. Which electricity company are you with, and what's the name of your tariff?

I say "if you want E7" because you then say:

moneysavinguser123 said:

We have electric underfloor heating

That;'s one of the most expensive ways to heat a property. With E7 the seven night-time hours are cheaper, but the seventeen daytime hours are even more expensive than normal. You might find that, depending how much you use the heating, switching to an E7 tariff will make your bills bigger.

Toddyken

Hi, I could have written this myself, same flat , same Megaflow and underfloor heating. Like you I’m trying to work out the best most economical way to run the electrics. I had someone out on Saturday from Domestic & General , firstly he advised me that out of 2 wires my immersion  heating wire has no connection, he tried to explain why I needed this , im the only person in the flat,,so if any body could explain why I would benefit from hot water tank and immersion  heater I would appreciate that, it’s down to whether I will be having the occasional bath and where the water sits ? On another note, I was on Economy 7 , therefore my underfloor heating would come on between 12am & 7 am, as it’s an old system it is very expensive to run, I was averaging £14 a day. After 6 weeks I have changed to Electric radiators , came off Economy 7 and have seen a big reduction in my Electricity consumption. I found with the UFH my apt was quite cold by mid-afternoon therefore made more sense to put the radiators on All day rate and use them when I need them. 

tamste

Or you could make the best of the E7 by installing HHR/SSH storage heaters? Bit expensive to install with HHR's getting close to £1000 each, but SSH's might work for you at ~£500 each. When I contacted the storage heater manufacturers recently I was told that the HHR's retain ~50% of the heat (if unused) whilst the SSH's are ~40%.

Gerry1

@Toddyken If you're using panel heaters during the day, make sure you're on single rate, not E7.

The E7 day rate will be much higher, and savings from hot water heated overnight probably won't be sufficient to compensate.   Do the sums !

snowqueen555

I've been reading storage heaters aren't very efficient, especially the older ones you find in some flats. I find myself in a situation where I may be buying a ground floor flat with no gas.

A lot of people seem to have no problems having the immersion on a few hours each day, and for heaters I will most likely try the newer infrared ones to heat certain sections of the flat/room/workspace, rather than try and heat the whole place with those convection ones.