Temporary use of electric 'instant' water heater

[JohnW2]

Thanks for asking but I can’t remember. I can check when I return to the UK for Christmas but that won’t be till 10th December.

No problem. As you will understand from my discussion,it might be interesting to know - whenever you can tell us!

However, to perhaps jog your memory ... if it is a manual mixer, it will have separate 'taps'for the hot and cold water, which you have to fiddle with to get the temperature and flow rate you want. If it's a thermostatic one, it will probably have just one knob to 'control temperature' and a separate one to control flow rate.

Kind Regards, John

 

[SUNRAY]

I didn't say it was impossible, simply impractical, because it takes so long.

I truly don't remember it being an issue

 

[JohnW2]

This should be in the plumbing section and the OP should crack on as he seems intent on doing - then update us with the results

There seems to be at least one deficiency in your suggested that approach .... some 30 hours after positing the question in the plumbing forum, during which time it have been viewed 71 times, I see this ...

So that is the nearest to an 'update' I can provide you with.

At least I got a fair number of early replies (and many within the first 30 hours) when I posted the question in this forum, even if most were (in a good few cases incorrect) answers to questions I had nor asked.

 

[SUNRAY]

So it seems big brother is watching, on of my suggestions via email being this:

This installation happens to be for pumped well water but look at 1 hour 20 minutes.

 

[JohnW2]

So it seems big brother is watching, on of my suggestions via email being this: ,videop. ... This installation happens to be for pumped well water but look at 1 hour 20 minutes.

Thanks, but what exactly am I meant to be looking at?

Kind Regards, John

 

[SUNRAY]

Thanks, but what exactly am I meant to be looking at?

Kind Regards, John

The simple thing to do is source a heater from abroad where it is common to use a single electric heater for the whole property. This will require the use of an expansion vessel.

I truly don't know what the difference is, but what I do know Is staying with relatives in Berlin, way back in 80's there were 11 of us in the house and in the morning there was simply no feeling of lacking hot water in 3 bath/shower rooms and kitchen. The heater was bigger than a typical shower unit by maybe a factor of 3 and being permanently pressurised by mains water the pressure vessel was bigger. They occupied the rear half of a kitchen base unit, so a chunky bit of kit.
I have no idea what power but the pair of overhead wires feeding 2 properties looked smaller than our typical feed to one property

 

[JohnW2]

Oh, do you mean that you just posted it to illustrate roughly what the bit of kit you experienced in Beerlin back in the 80's looked like? If so, thanks,

However, I have to say that I do not fully understand what's going on in that plumbing arrangement, and nor do I know whether the heater is supplying one tap, a dozen showers or something in-between

Kind Regards, John

 

[JohnW2]

This should be in the plumbing section and the OP should crack on as he seems intent on doing - then update us with the results

Given that it seems unlikely that there will be any more developments in this situation, I can now 'update you' at least as regards the results of taking your advice and asking my question in the Plumbing/Heating forum ...

... well over 4 days after I posted the same question in the Pluming/Heating forum, no-one there seems to have had anything to say (useful or otherwise), despite about 80 'views' of my question, and since my OP is now near the bottom of 'Page 5' in that forum, I rather doubt that there will be any 'further' replies. It therefore seems that your undoubtedly well-intentioned advice was not quite as helpful as you may have expected it to be. As for ...

..... the OP should crack on as he seems intent on doing - then update us with the results

As I've said before, it was never my intention to do anything until I had canvassed as much opinion/advice as I could, but having now reached that stage (including some useful input from this forum) I am, indeed, going to 'crack on' with some experiments, as I will describe in a separate post. Particularly given the time of year, that will take at least a few weeks, so it's likely to be well into next year before I can update you as to the results of those experiments.

 

[scousespark]

In case Mr Jobsworth is around, there is already an (unused) 40A shower circuit present, which was installed 'just in case' an electric shower was ever needed (which I doubt it ever will), so I could use that circuit for a water heater - so that, since what I'm suggesting would require neither a 'new circuit' nor any electrical work in a bathroom, it presumably would not be notifiable, at least as far as Part P is concerned.

Kind Regards, John

If there is no shower in the bathroom, it woold be a stretch to say there is a circuit. If this was a pro installation, there would be an EIC. Surely this is a new circuit.

 

[davelx]

If there is no shower in the bathroom, it woold be a stretch to say there is a circuit. If this was a pro installation, there would be an EIC. Surely this is a new circuit.

If you have a RFC or radial FC with nothing plugged in, it is still classed as a circuit. How is the above any different?

 

[JohnW2]

If there is no shower in the bathroom, it woold be a stretch to say there is a circuit. If this was a pro installation, there would be an EIC. Surely this is a new circuit.

Good to see you, and I hope that all is well with you and yours.

I have to say that your view doesn't really corresponds with what I would regard as common sense, even though I cannot deny that, if taken literally, the BS7671 definition implies that if there is wiring (originating at a CU/DB, and protected by an OPD) which had no connected 'electrical;' equipment,then it is not "a circuit".

Addressing first the details you mention, it was a "pro installation" and there is an EIC - and, in any event, there should be an EIC even if it had not been a 'pro install'. If you're suggesting that what they installed was not 'a circuit', what would you call it?

Would you have a different view if this <whatever you call it> (at the time connected to nothing) had been labelled "Water Heater" where it originates at the CU, rather than "Shower" (which it currently says)?

When the property was re-wired, about 20 years ago, it was totally empty, with no hard-wired electrical loads at all, other than lighting. As I've explained, they installed a shower circuit "in case an electric shower was installed in the future" (even though there was no shower at the time, and still isn't'. They similarly installed a cooker circuit, an immersion circuit and an 'outside lights' circuit "in case an electric cooker, immersion heater or outside lighting was installed in the future" (even though none of those things were installed at the time,and still aren't).

Are you really suggesting that (despite BS7671 definition) it is sensible or useful to say that none of those are 'circuits' - and therefore that, by implication, if anyone ever connects anything to <whatever you wish to call them>, they would thereby be 'installing a new circuit"??

I have to say that suggestions such as you have made (which some might call 'pedantic') are probably one of the things which "give a bad name" to rules, regs and laws and thereby very probably reduce the extent to which some people take them seriously.

Kind Regards, John

 

[SUNRAY]

Oh, do you mean that you just posted it to illustrate roughly what the bit of kit you experienced in Beerlin back in the 80's looked like? If so, thanks,

However, I have to say that I do not fully understand what's going on in that plumbing arrangement, and nor do I know whether the heater is supplying one tap, a dozen showers or something in-between

Kind Regards, John

That particular installation is fed by a well pump, so the pressure gauge and switch are to do with that.
That is the domestic hot water system supplying a whole house, exactly what's I don't know. However the taps and pipework etc will very likely be similar or even the same as those on a vented cylinder/cistern system or combi boiler.
In a system fed by mains water pressure the gauge or pressure switch would not be required, such as; the house in Berlin and a holiday Git in France far more recently although it was bigger to cope with an 8 bedroom property plus sauna, hot tub and swimming pool changing room showers (no it didn't heat the pool, that was ASHP).
In a system fed by mains water pressure, without looking in to it deeply, I'd guess it will only require a non return valve in the cold supply to prevent contamination (just the same as any shower, or for that matter anything else, where the outlet is capable of reaching the standing water in shower tray or bath etc.). Oh and possibly a PRV.

The system I describe certainly works with mixer taps, whether manual or thermostatic and should present the same water pressure and the incoming cold.

 

[JohnW2]

That particular installation is fed by a well pump, so the pressure gauge and switch are to do with that.

That's what I assumed.

That is the domestic hot water system supplying a whole house, exactly what's I don't know. However the taps and pipework etc will very likely be similar or even the same as those on a vented cylinder/cistern system or combi boiler. ... In a system fed by mains water pressure the gauge or pressure switch would not be required, such as; the house in Berlin and a holiday Git in France far more recently although it was bigger to cope with an 8 bedroom property plus sauna, hot tub and swimming pool changing room showers ...

Again, that's as I assumed. However, you said that the house in Berlin had a 'pressure vessel'- why was that needed, I wonder?

In a system fed by mains water pressure, without looking in to it deeply, I'd guess it will only require a non return valve in the cold supply to prevent contamination (just the same as any shower, or for that matter anything else, where the outlet is capable of reaching the standing water in shower tray or bath etc.). Oh and possibly a PRV.

Again, as I expected - but, as above, why the 'pressure vessel' in Berlin

The system I describe certainly works with mixer taps, whether manual or thermostatic and should present the same water pressure and the incoming cold.

That's what I would imagine/hope.

The only issues I can really see relate to the achievable flow and temp. With thermostatic mixers such as the one whose spec was posted by flameport, the requirement for outlet temp to be at least 12 below input tempo means that some mixing with cold water will be required - whereas, in contrast, with an electric shower, the heater water is not diluted by addition of any cold water. I would therefore expect that the temp achieved for a given flow rate would (or the flow rate for a given temp) would be a bit lower with the water heater and thermostatic mixer than with an electric shower of the same electrical power - but how much lower' remains to be seen!

With a water heater and a 'manual' shower mixer, I would expect the performance to be similar/same to that of an electric shower of the same electrical power (if the 'cold tap' of the mixer were turned completely off).

Kind Regards, John

 

[SUNRAY]

It's a safety feature. If the cold supply goes away, any hot is shut off completely to avoid scalding or worse.
Without that, hot water at whatever temperature it was supplied at would be provided from it, which could be a very high and dangerous temperature.

If you were expecting to just supply hot to the mixer then forget it - not going to work.
It's probably a total bust anyway, as an instant heater won't be able to provide water that's hot enough to mix with cold to give a suitable shower temperature.
See example specifications below - hot must be 12C more than the outlet temperature and suggested at 60C+, which isn't going to happen unless the flow from the hot heater is barely a trickle.
Other valves may vary, but these specs are pretty common.

View attachment 322184

The unit I installed only requires the cold pressure to function ie it will provide a cold shower with no hot. which was really confusing as the thermostatic cartridge had been inserted round the wrong way and trying to get water out of it with only the cold connected didn't happen.

 

[SUNRAY]

That's what I assumed.

Again, that's as I assumed. However, you said that the house in Berlin had a 'pressure vessel'- why was that needed, I wonder?

Again, as I expected - but, as above, why the 'pressure vessel' in Berlin

I can only assume to cater for latent heat expansion, that is assuming there is no cold water booster upstream of the heater

That's what I would imagine/hope.

The only issues I can really see relate to the achievable flow and temp. With thermostatic mixers such as the one whose spec was posted by flameport, the requirement for outlet temp to be at least 12 below input tempo means that some mixing with cold water will be required - whereas, in contrast, with an electric shower, the heater water is not diluted by addition of any cold water. I would therefore expect that the temp achieved for a given flow rate would (or the flow rate for a given temp) would be a bit lower with the water heater and thermostatic mixer than with an electric shower of the same electrical power - but how much lower' remains to be seen!

With a water heater and a 'manual' shower mixer, I would expect the performance to be similar/same to that of an electric shower of the same electrical power (if the 'cold tap' of the mixer were turned completely off).

Kind Regards, John

I didn't look at FPs post before post #74. I know ours has a different spec but trying to identify it now is going to be tricky.

I've worked on lots of big hot water systems and can work my way round most plant rooms where pressure vessels are common place for various reasons but I'll not pretend to be an expert but even less so on small domestic systems.

I'll just add I've seen one or two more abroad than those I've mentioned and I believe all have included the vessel, maybe for safety; afterall a sealed system + heat = increased pressure. I don't know about you but I never heated a sealed 1 gallon oil can with a blowtorch to see if it split