Hot water

[csearle]

So that's fine, but I was just wondering about the tank of water we heat up every night (and have done for years). After we fit the shower, we'll definitely not need to heat up 120 (I think) litres of water, more like 4 sink fulls a day. Could we get a smaller tank and save a bit of cupboard space or even an 'on demand' water heater like the shower for example? Or are the costs likely to outweigh and potential benefits. The tank is well insulated and the water is nice and hot even 24 hours later, so I guess there's not that much electricity used in getting the tank up back up to temeperature again.

FWIW my thoughts are that, as you say, the current arrangement only has to replace the heat you have used + any that's esacaped into your dwelling so it probably isn't too wasteful.

The most convenient instant water heaters are usually electric so the cost per litre might be more. I imagine tiny gas boilers for sinks are still available though.

I feel an experiment is in order involving your gas meter or your immersion heater. Maybe a measurement too of how much water you actually use from the hot taps in one day. I'm sure someone of your abilities could get to the bottom of this.

Regards,
Chris

[pendas]

You can either get a shorter heater element for the cylinder or a dual length one with two thermostats to avoid heating the whole cylinder of water.

[csearle]

You could temporarily disconnect your immersion heater cable, put a plug on it if it'll fit, then at midnight, plug it in to a socket via one of those cheap measuring devices until morning. Hopefully that'd show how much electrical energy (and therefore cost) it had taken to restore the tank to its previous state. You could do this after various numbers of "no-heating-nights" to see if there is any advantage to be gained. I can fully sympathise if you felt this was all too much bother!

Chris

[PrincessB]

Yeah, I guess you're right Chris. I have seen these small geyser type hot water heaters in workplace canteens for example and wondered if there was a more domestic equivelant.

Redring sell a 12kw inline water heater.

https://www.energybulbs.co.uk/redring+1 ... ater+(rp12)/2821466957?gclid=CJLuxd2dldMCFTIo0wodoToCqw

I considered one of these to heat the water for the kitchen sink which is about as far away from the hot water tank as you could manage with the sink and the tank remaining in the same house!

You would need to upgrade the wiring to take that amount of current.

It's one option,

B.

[chas49]

You could temporarily disconnect your immersion heater cable, put a plug on it if it'll fit, then at midnight, plug it in to a socket via one of those cheap measuring devices until morning. Hopefully that'd show how much electrical energy (and therefore cost) it had taken to restore the tank to its previous state. You could do this after various numbers of "no-heating-nights" to see if there is any advantage to be gained. I can fully sympathise if you felt this was all too much bother!

Chris

A 3kW immersion heater should not be plugged into a 13A ring circuit (if that's what you're suggesting). It needs a fixed radial circuit fused at 15 or 16A (which is probably what it's on).

So plugging into a cheap measuring device might not be a good idea!

[csearle]

You could temporarily disconnect your immersion heater cable, put a plug on it if it'll fit, then at midnight, plug it in to a socket via one of those cheap measuring devices until morning. Hopefully that'd show how much electrical energy (and therefore cost) it had taken to restore the tank to its previous state. You could do this after various numbers of "no-heating-nights" to see if there is any advantage to be gained. I can fully sympathise if you felt this was all too much bother!

Chris

A 3kW immersion heater should not be plugged into a 13A ring circuit (if that's what you're suggesting). It needs a fixed radial circuit fused at 15 or 16A (which is probably what it's on).

So plugging into a cheap measuring device might not be a good idea!

The word temporarily was key here Charles. I was not suggesting that this be done permanently, just as a way of measuring the power consumption for a night or two.

There is nothing very unsafe about plugging a domestic 3kW immersion heater into a socket, be that a socket on a ring final circuit or a radial circuit. The reason is that those circuits are designed to be able to supply 13A to whatever is plugged in, for example a kettle. The reason we put them on their own radial circuit is that they are a more continuous load, which would render the diversity applied to standard final circuits slightly invalid. This is inapplicable during an experiment overnight and hardly worth raising an eyebrow over even during other times.

The protective device's rating is chosen to protect the cable, so it need not be 15A/16A, for example if the cable had a cross-sectional area of 4sqmm and was clipped directly to the fabric of the building then you could use a device rated at 32A. Obviously it also has to be greater than 13A so that it doesn't trip under normal load conditions.

Even the cheap measuring devices are rated at 13A so they too are safe.

Regards,
Chris
(Electrician)
PS I would add though that plugs and sockets are not wonderful things generally so that is another reason we wouldn't use then for known high loads of long duration.

[chas49]

Thanks for the clarification. Hopefully anyone reading this topic will take note and not do anything without getting advice from an electrician first!

[DrFfybes]

Irrespective of the cost side of thing, you will have a store of hot water that can be heated by the boiler OR electricity.
This is extremely useful when the boiler pack in.

Also you currently use an electric shower, this runs on mains cold water and so a higher output electric shower than you have now might require new wiring for the extra output.

If you really wanted to go the whole hog, get a pressurised HW cyl and a mixer-tap shower, then you will get a stonking shower pressure and a reservoir of hot water.

Paul

[csearle]

Irrespective of the cost side of thing, you will have a store of hot water that can be heated by the boiler OR electricity.
This is extremely useful when the boiler pack in.

AIUI Snorvey doesn't have a boiler* but rather just immersion heater(s).

Chris
* because he refers to cheap price electricity, which is often associated with dwellings without gas etc.