2kw immersion element

[Ucatchmydrift]

Hi, have any of you knowledgeable chaps/chapes'es came accross an immersion heater element that is 11" (14" would also fit i think), is suitable for hard water areas, has a 2.25" bsp thread, and is 2kw, for a reasonable price (i call under £50 reasonable!)?

(i cant find one!)
(btw my inverter is 3kw)

As this is literally the last thing i need to switch over to my semi- off grid setup.

My immersion tank is 110ltrs and has two elements. I have found the top one on boost for 1 hour (3kw) is enough for a deep bath, so 2kw presumably should take about 1/3 extra time to heat up, which is fine as can be on a timer. Also, i will be using it for a shower mostly, (one of those tap push on shower jobbies) so, even less time id have thought to heat up enough water for a shower.

I could use two 1kw elements in series at a guess, but that comes out at £80+, which seems alot as a 3kw is about £20, presumably as they make so many of them.

Unless anyone knows of a way to reduce the power from a 3kw to a 2kw for a reasonable price? (im doubting this)

Thanks

 

[ProDave]

Two 1kW heaters in series would give you a good deal less than 1kW total. It would need to be two 1kW heaters in parallel.

 

[Ucatchmydrift]

Two 1kW heaters in series would give you a good deal less than 1kW total. It would need to be two 1kW heaters in parallel.

Sorry, yes, parallel.

 

[johnb2713]

Hi, have any of you knowledgeable chaps/chapes'es came accross an immersion heater element that is 11" (14" would also fit i think), is suitable for hard water areas, has a 2.25" bsp thread, and is 2kw, for a reasonable price (i call under £50 reasonable!)?

(i cant find one!)
(btw my inverter is 3kw)

As this is literally the last thing i need to switch over to my semi- off grid setup.

My immersion tank is 110ltrs and has two elements. I have found the top one on boost for 1 hour (3kw) is enough for a deep bath, so 2kw presumably should take about 1/3 extra time to heat up, which is fine as can be on a timer. Also, i will be using it for a shower mostly, (one of those tap push on shower jobbies) so, even less time id have thought to heat up enough water for a shower.

I could use two 1kw elements in series at a guess, but that comes out at £80+, which seems alot as a 3kw is about £20, presumably as they make so many of them.

Unless anyone knows of a way to reduce the power from a 3kw to a 2kw for a reasonable price? (im doubting this)

Thanks

If you put a diode in series with the 3kW element you will get 1.5 kW. You could also add a switch across the diode so you have full or half power.

 

[Ucatchmydrift]

If you put a diode in series with the 3kW element you will get 1.5 kW. You could also add a switch across the diode so you have full or half power.

Ok thanks, not sure im following though? I thought the only thing a diode would do would allow only one way, but thinking about it, as its ac, then does that make it different? (im not an electrician as you can probably tell lol)

Im guessing you only get a half sign wave kinda thing lol? - like from positive to 0 current, and not the other half? - difficult to explain.

Would the element cope with that? Im guessing it would as its just seeing half the current that it would normally? - cant be that simple though can it?

 

[Ucatchmydrift]

Also, i was hoping for 2kw as 1 or 1.5 may take just a bit too long to heat the water! (cant use the inverter for 3kw as ill already be running the house load, and would overload it)

 

[UNG]

There are 2Kw immersion heaters available just not within your reasonable price bracket although I'm not unduly surprised as a 2Kw immersion heater has more of a niche market that probably doesn't warrant the large manufacturing volumes to keep the price down

 

[Ucatchmydrift]

There are 2Kw immersion heaters available just not within your reasonable price bracket although I'm not unduly surprised as a 2Kw immersion heater has more of a niche market that probably doesn't warrant the large manufacturing volumes to keep the price down

Yes, the cheapest i could find was £76 plus postage etc. More than i would like to pay.. Looking into the diode idea..

 

[johnb2713]

Ok thanks, not sure im following though? I thought the only thing a diode would do would allow only one way, but thinking about it, as its ac, then does that make it different? (im not an electrician as you can probably tell lol)

It would supply just one half of the AC waveform and therefore half the power.

Im guessing you only get a half sign wave kinda thing lol? - like from positive to 0 current, and not the other half? - difficult to explain.

Correct

Would the element cope with that? Im guessing it would as its just seeing half the current that it would normally? - cant be that simple though can it?

Yep, thats exactly right.

In terms of your inverter, if youre running it as a grid tied inverter, it wouldnt overload it with the 3kW plus house load, it would simply output it's maximum and then add more from the grid.

 

[Ucatchmydrift]

It would supply just one half of the AC waveform and therefore half the power.


Correct


Yep, thats exactly right.

In terms of your inverter, if youre running it as a grid tied inverter, it wouldnt overload it with the 3kW plus house load, it would simply output it's maximum and then add more from the grid.

Thanks . Its not grid tied no, i have a hybrid inv with 14.4kw diy storage, and only have grid supply to the inv at economy 7 times via a contactor via a wifi smart plug. So really need an element of about 2.2kw max just to keep the strain off the inverter. Im guessing if i were to do the diode trick and over spec the diode say 25-50% it wont get hot, with any luck, and all should be good.
Only issue will be if i were to suddenly need hot water for a shower etc, id have to wait about 1.5- 2hrs using just 1.5kw. Which would be fine normaly on a timer, just a bit slow if wanting hot water at an unusual time.
This is all simply to get around using the 8kw power shower! - thats the last thing im actually running off the grid now.

 

[johnb2713]

Thanks . Its not grid tied no, i have a hybrid inv with 14.4kw diy storage, and only have grid supply to the inv at economy 7 times via a contactor via a wifi smart plug. So really need an element of about 2.2kw max just to keep the strain off the inverter. Im guessing if i were to do the diode trick and over spec the diode say 25-50% it wont get hot, with any luck, and all should be good.
Only issue will be if i were to suddenly need hot water for a shower etc, id have to wait about 1.5- 2hrs using just 1.5kw. Which would be fine normaly on a timer, just a bit slow if wanting hot water at an unusual time.
This is all simply to get around using the 8kw power shower! - thats the last thing im actually running off the grid now.

May be a daft question, but why not grid tie it?

 

[binky]

This is all simply to get around using the 8kw power shower! - thats the last thing im actually running off the grid now.

So at say 15mins for a good shower, at 40p per kWh, that's 80pence. How much are you going to spend to save that money?

Most obvious answer to me is to use a solar diverter such as Solic which can handle a 3 kw immersion. The booster element at the top of the tank should be sufficient for a quick wash, but a funny thing is that these elements will never heat the full tank of water due to stratification ie the water doesn't mix itself with cold water lower down the tank.

 

[Ucatchmydrift]

So at say 15mins for a good shower, at 40p per kWh, that's 80pence. How much are you going to spend to save that money?

Most obvious answer to me is to use a solar diverter such as Solic which can handle a 3 kw immersion. The booster element at the top of the tank should be sufficient for a quick wash, but a funny thing is that these elements will never heat the full tank of water due to stratification ie the water doesn't mix itself with cold water lower down the tank.

Well, as little as possible is the answer! . If i can just add a diode for £10, then thats great...

The tarrif im moving too is utilita, 5p kw/h economy 7 rate. 90p kw/h for the first PEAK kw used each day, as there is no standing charge. So, for a shower each day, thats about £0.90. - so, defeats the point of me switching to that tarrif. With a 2kw element, i can use the battery storage charged from the 5p rate overnight, saving me 85p a day. And based on my daily usage of 8kw, i will never have to pay more than a total of £12 a month in bills! - which is great. I will litterally never have to use peak elec again with my setup. (of which, the shower is now the only thing stopping this).

(whenever i have a bath, i only ever use the boost function of the immersion, and i put it on for 40 mins to 1 hour (3kw element), and this is plenty for a deep bath, and this is using the top element in the tank (115ltr tank) )

There wont be much spare pv for the diverter for most of the year as i only have 3kw pannels and 14.5kw storage, so most will go to the storage. My setup is 100% diy and very differnt to most, with no grid tie etc. All seperate off grid system but with inverter pass through if needed.

Looking at pictures online, the diverter would be after the inverter, so how would it generate 3k if my inverter for example could only allow 2.5kw? (based on grid supply to the inverter is switched off)

 

[Ucatchmydrift]

May be a daft question, but why not grid tie it?

Im not sure what the benefits for grid tie for me would be? Wont be making much to send to the grid, most will be used for battery storage, plus, have to pay someone to connect it all up, certificated etc, plus a new inverter, and how much do they pay you these days for a kw/h? Thought it was about 5p?

 

[Murdoch]

Im not sure what the benefits for grid tie for me would be? Wont be making much to send to the grid, most will be used for battery storage, plus, have to pay someone to connect it all up, certificated etc, plus a new inverter, and how much do they pay you these days for a kw/h? Thought it was about 5p?

what else are you powering apart from your immersion ?

 

[BorisJ]

A diode will certainly halve the immersion power but I’m not sure your inverter will like half waving that amount of current.

 

[Ucatchmydrift]

what else are you powering apart from your immersion ?

The whole house... Thats the only thing left i need to sort out now.

 

[Ucatchmydrift]

A diode will certainly halve the immersion power but I’m not sure your inverter will like half waving that amount of current.

Ok yes, good point, not sure how that would react. Probably best just to use 2x 1kw in parallel, simplest is usually the best. I guess £80 is worth it, as itll pay for its self in about 100 days or so.

 

[binky]

Looking at pictures online, the diverter would be after the inverter, so how would it generate 3k if my inverter for example could only allow 2.5kw? (based on grid supply to the inverter is switched off)

They release energy in bursts, so you can power a 3kw resistive load from as little as 50W - clever stuff. It's also why you can't have any electronic controls, the pulses trash them. What I have done in the past is wire the immersion control in parallel with the existing supply/ timers. This allows the immersion to be fed from two sources to ensure sufficient hot water mid winter.

3kw of panels isn't a lot for what you are doing. Are you trying to go completely off grid? Or just set the solar system up that way?

 

[Ucatchmydrift]

They release energy in bursts, so you can power a 3kw resistive load from as little as 50W - clever stuff. It's also why you can't have any electronic controls, the pulses trash them. What I have done in the past is wire the immersion control in parallel with the existing supply/ timers. This allows the immersion to be fed from two sources to ensure sufficient hot water mid winter.

3kw of panels isn't a lot for what you are doing. Are you trying to go completely off grid? Or just set the solar system up that way?

Ok I see.. don't think that will work so well then for me..
Not completely off grid as in the winter I charge the batteries only ever at economy 7 times, currently 8.8p edf(from january). The panels are on two shed roofs, so i was able to diy it. No more space for any more unless i put them on the roof, and I can't do that diy. And if I move in a couple of years, be difficult to take them with me. All what I've done is removable. And only cost £3500 for everything. 3kw panels, 3k hybrid inverter, 14.4kw diy batteries. Separate double sockets in each room ofnthe house etc. It's a budget build that works extremely well..