Dual immersion for bigger bath?

[88v8]

I plan to put in a deeper bath. Which holds more water. Up to 90 gallons.
The purpose of a deeper bath is so I can have a nice wallow, which I can't in the present one.
So the standard cylinder 36" x 18" that holds around 25 gallons will no longer be large enough. Or will it...?

I could put a taller cylinder in the airing cupbd, but not a wider one.

Would I get more hot water from a dual immersion cylinder the same size? The Gledhill 900 for example.
We are on Economy 7.

I know that usually the bottom immersion is switched overnight and the upper one used for topping up, but I could use it the other way and could switch both immersions on if taking a bath, and just the top one otherwise.
The cylinder only feeds one basin and the bath, and the bath isn't used every day. The kitchen has a separate heater and we have an electric shower.

What do you think?

 

[88v8]

Bump... so do I get more hot water from a dual cylinder?

 

[oldbuffer]

No, but it would re-heat quicker.

 

[JohnD]

Bump... so do I get more hot water from a dual cylinder?

No, you get more hot water from a bigger cylinder

You can't power two immersion heaters from one normal circuit.

Haven't you got a gas boiler?

 

[88v8]

No, all electric.
I can use the feed from a redundant 9kw shower.

I thought / hoped the lower immersion would heat the cylinder top to bottom instead of stratification.

 

[JohnD]

I thought / hoped the lower immersion would heat the cylinder top to bottom instead of stratification.

It will.

All the water above itself.

It will still stratify but there will not be much cold below. It will take longer. A 3kW immersion heater takes about one minute per litre. Older cylinders are usually around 100 litres which is about a normal bath. Luckily you can afford to pour money down the drain.

 

[flameport]

The way to get more hot water is to wire the immersion heaters in the way that USA hot water heaters are arranged.
Top element has a changeover thermostat, so when power is applied that heats the top of the cylinder quickly, and when that's up to temperature the thermostat disconnects that and power is sent to the lower element with it's own thermostat.

That way you get hot water at full temperature quickly, as you don't have to wait for the whole cylinder to heat up, but you still get the whole cylinder heated if you wait long enough.

 

[88v8]

The way to get more hot water is to wire the immersion heaters in the way that USA hot water heaters are arranged.
Top element has a changeover thermostat, so when power is applied that heats the top of the cylinder quickly, and when that's up to temperature the thermostat disconnects that and power is sent to the lower element with it's own thermostat.

Thankyou.
Never heard of that option. So only needs one feed. A quick look suggests low amps, requires a relay I guess.
Further investigation.

I could interpose a manual switch to turn off the lower stat for days when we won't need the extra water.

Luckily you can afford to pour money down the drain.

Haha, yes that's one way of looking at it. Although not as bad as outdoor hot tubs. Collectively the typical house discards a lot of hot water, shame there's no economic way to recover the heat.

 

[flameport]

Never heard of that option. So only needs one feed. A quick look suggests low amps, requires a relay I guess.

No relay, it's just a thermostat with a changeover contact. Power consumption is the same 3kW as for any other element.

 

[bsr]

The other option would be to turn up the temperature so you can use less hot and more cold. I think most immersions can go up to 80 degrees?

 

[88v8]

The other option would be to turn up the temperature so you can use less hot and more cold. I think most immersions can go up to 80 degrees?

Yes, they can, but one is likely to burn one's bottom at 80C.

No relay, it's just a thermostat with a changeover contact. Power consumption is the same 3kW as for any other element.

OK, errm, like this?

 

[bsr]

Yes, they can, but one is likely to burn one's bottom at 80C.

You mix the hot with the cold in the bath?

 

[flameport]

OK, errm, like this?

That is a changeover thermostat but not for an immersion heater.

Actual immersion thermostats with 3 connections appear to be unobtanium in the UK.

 

[BlueLoo]

The other option would be to turn up the temperature so you can use less hot and more cold. I think most immersions can go up to 80 degrees?

Exactly.