Hot water cylinder size

[Lower]

I'm in the process of starting a renovation of our bathroom which will involve a new bathroom suite and moving of the sink, bath, toilet etc.

It will also involve removing the current electric shower and i plan to replace it with a pumped shower taking hot water from the hot water tank.

The current hot water tank is approx 30 years old and also encroaches into the bathroom quite a lot. I want to replace it with a narrower diameter one but have two questions:

1. We will have two showers in the house that the hot water cylinder will supply. What volume cylinder should i be going for to supply that sort of demand?

2. Are the heat exchangers in modern hot water cylinders more efficient than the old ones? I'm wondering what sort of reheat time a modern cylinder would need.

Thanks in advance.

 

[BigBurner]

A few Qs

1. How many bathrooms (assume two)

2. Is there access in the loft?

3. Is the cold mains pressure OK?

Power shower pumps exhausts a cylinder very quickly and if two showers, you will have only a few minutes in the shower, if that. It may be worth your while buying a new high flow combi and put it in the loft, then lots of space saved. New models use far less gas.

 

[Lower]

Two bathrooms, but there's only two of us in the house.

There is access in the loft, but the object of this exercise to avoid having to fit a new boiler.

Cold mains pressure is good.

We have considered fitting a new combi boiler, but the existing boiler is fine and i don't want to have to go to the expense of fitting a replacement. Our existing heating system is vented and therefore unpressurised and i have sneaking feeling that there is a slight leak somewhere in it, probably under the concrete floor in the kitchen so i want to avoid fitting a new boiler which would inevitably run at a higher pressure.

Hence wondering about fitting a new cylinder that would have a much lower recovery time than our existing cylinder but wondered what size to get as a minimum.

 

[JohnD]

most cylinders are about 117 litres and take (with a modern pumped boiler) about 20 minutes to heat up from cold. They are either tall and thin or short and fat. This is ample for a hot bath. You can get bigger cylinders.

Run a tap into a bucket and see how many litres per minute you think your shower should have, and multiply this by the number of minutes you want to spend under it.

A power shower can use a vast amount of water, unless you are quick it will use more than a bath. And it all goes straight down the drain. Your cold water tank will also have to store enough water for your showers, soiince it will refill much slower than your pump empties it.

 

[BigBurner]

You need the space and to get what you want you will need a large cylinder plus pump(s). Not cheap. A few option:

1. Externally mounted (saves lots of space) high flow multi-point water heater like this:
http://www.discountedheating.co.uk/shop/acatalog/Andrews_WX42_NG_External_Water_Heater.html

Rinnai also do similar models

2. A additional combi to do the DHW only - may as well get it do the heating as well. Just because your existing boiler is newish does not mean it cannot be replaced.

3. A tall thin heat bank like the Pandora:
http://www.heatweb.com

4. From:
http://www.advanceappliances.co.uk/gas_or_oil_thermal_store_systems.html

They do DHW only and DHW & CH thermal stores too. May as well get your CH off it as well and go the whole hog - worth it.

5. Shower Coil Cylinder:
http://www.copperform.co.uk/mains_pressure/ultra_shower/index.htm
This is a vented cylinder with a shower coil inside fed by high pressure mains water.

 

[kevplumb]

well that gave the game away

how yer doing salesman

 

[BigBurner]

What didn't you understand about my post?