New hot water cylinder

[Schmill]

Ok, firstly I have a vented gravity fed indirect hot water system with cold tank in the loft.
I am fed up of running out of hot water in the mornings so am looking to change the cylinder, but not sure what i need.
At the moment I have worked out that with 65c hot water, 15c cold water, and a shower mix running at 40c at 10L/min and 10 minute shower it will use 50L of hot water. With 4 people thats 200L, so I think i need around a 250L tank.
This also seems to agree with other info i've seen that says to allow 50L per person, then another 50L.
Does this sound about right?

At this point where do I go from here? There seems to be many brands of cylinders around, is there much difference in them? Are there any that are recommended, or should be avoided?

Many thanks

 

[Agile]

I always quote 50 li plus 50 li per person.

There are many brands and little difference for a vented cylinder.

You should have the system checked to ensure the reheat is the best comensurate with providing central heating at the same time.

Tony

 

[Schmill]

You should have the system checked to ensure the reheat is the best comensurate with providing central heating at the same time.

Not entirely sure what this means, but are you effectively saying to have it checked to make sure that the boiler is 'man-enough' to be able to run the central heating and also heat the new larger HW cylinder?
As I have various bit of paperwork available is this something I could work out for myself from the heat output of the boiler etc?

We are planning to have our boiler changed at some point, but not for a few years hopefully

 

[Agile]

All it means is that because modern cylinders have a greater heat input as the coil is larger, the balance settings should be checked.

This is to to ensure that as much heat is available to reheat the cylinder as the boiler system is capable of giving whilst still allowing some heat to the rads.

Tony

 

[Schmill]

Aha I see, thanks

So pretty much, as long as it is an indirect cylinder of the correct litrage, is of a size that will fit in the cupboard, and is suitably lagged it's just a case of finding a nice cheap cylinder somewhere and pretty much ignoring the branding?

 

[Agile]

Yes, but because copper is expensive they are not cheap and expect to be paying well over £200 !

Here is an example which is £345 :-

http://www.cylindersdirect.co.uk/index.php?main_page=product_info&cPath=1&products_id=26

Tony

 

[Schmill]

Many thanks Tony.

What is the advantage / disadvantage to the Stainless Steel cylinders I have seen on some sites, (other than they seem to be even more pricey!)

 

[mysteryman]

You should be changing to a fully pumped system with proper thermostatic control of the cylinder. This will give a faster reheat, and total storage volume is less significant. It is the ability to transfer heat into the cylinder which is important. Cheaper cylinders are less good at this. Look at the kilowatts rating of the coil and get a reasonably close match to your boiler output.

Gravity primaries are wasteful.

 

[Schmill]

Thanks MysteryMan, at first your post confused me so I did some further research...

I though that because my hot & cold water were 'gravity fed' (ie. it is the pressure of the water stored in the loft that 'pushes' the water out of the hot and cold taps), I had a gravity fed system.
Looking at it in more detail, I believe I have a fully pumped system...

Cold tank in the loft, hot tank in the airing cupboard. Also in the cupboard is my pump and 2 motorised valves, one for heating, one for hot water. Hot water cylinder has a themostat strapped to the outside that controls the HW motorised valve, and downstairs there is a thermostat in the hall that controls the CH motorised valve.

Hopefully that makes things clearer, sorry for any confusion.

I've also just measured my existing Hot water tank, and it is 450mm diameter, and around 900 tall, which looking online seems to make it around 117 Litres, so that might explain why we run out of hot water!

 

[Schmill]

Yes, but because copper is expensive they are not cheap and expect to be paying well over £200 !

Here is an example which is £345 :-

http://www.cylindersdirect.co.uk/index.php?main_page=product_info&cPath=1&products_id=26

Tony

Looking on that same site they have their 255 L cylinder:

http://www.cylindersdirect.co.uk/index.php?main_page=product_info&cPath=1&products_id=28

Which is £398, whilst still pretty damn expensive for a copper drum, it DOES seem quite a bit cheaper that the other sites I have looked on. Am I missing something, some hidden costs, or are they just good value?

 

[Agile]

The stainless cylinders you read about are for unvented installations and are about £900.

That firm seems to be a manufacturer who supplies direct to the public so may be a bit cheaper than B&Q etc.

Tony

 

[Whitespirit66]

Thanks MysteryMan, at first your post confused me so I did some further research...

I though that because my hot & cold water were 'gravity fed' (ie. it is the pressure of the water stored in the loft that 'pushes' the water out of the hot and cold taps), I had a gravity fed system.
Looking at it in more detail, I believe I have a fully pumped system...

Cold tank in the loft, hot tank in the airing cupboard. Also in the cupboard is my pump and 2 motorised valves, one for heating, one for hot water. Hot water cylinder has a themostat strapped to the outside that controls the HW motorised valve, and downstairs there is a thermostat in the hall that controls the CH motorised valve.

Hopefully that makes things clearer, sorry for any confusion.

I've also just measured my existing Hot water tank, and it is 450mm diameter, and around 900 tall, which looking online seems to make it around 117 Litres, so that might explain why we run out of hot water!

Yes, you're right. I think there is some confusion over gravity. Mysteryman has (correct me if I am wrong) taken 'gravity fed' to mean gravity hot water.

By saying gravity fed, you are referring to the fact that water is fed from tanks in the loft to the cylinder.

Gravity hot water is something completely different. This is an old-fashioned system where instead of the primaries from the boiler to the cylinder being pumped, they rely on a convection cycle, ie. hot water rising from the boiler to the cylinder and cooler water falling from the cylinder back to the boiler. This system obviously relies on the boiler being lower than the cylinder.

Hope this clarifies things.

 

[Schmill]

Agile; Thanks for the clarification on the stainless steel cylinders.

WS; Yeah, after researching further I came to the same conclusion as you, that Mysteryman thought I had one of the 'convection' based primary systems, rather than the pumped primary that I have. it is just the secondary(?) (the hot / cold water) that is gravity fed, but I am planning on fitting a pump for the shower on that too, (all other outlets will still be 'gravity fed' though).

I'm guessing then it will be a bit of saving, then a Cylinder from cylindersdirect

A quick question though... in my searching I have come across these cylinders with 'quick recovery' coils, which seem to just be a tighter, more compact coil within the tank, and therefore a smaller tank, (as it can reheat 'during use' quicker). Does anyone have experience of these, and are they any good? Just wondering if rather than storing masses of hot water, I should be looking at a quick recovery system instead if they are any good, and then I get to keep more of the airing cupboard space, rather than it being swallowed up by hot water storage!

 

[mysteryman]

Yes, I did think you meant gravity primaries.

You are correct about a high recovery coil - you can get small cylinders with a high recovery coil. These will reheat in a few minutes. There used to be Albion Superduty or Centerbrand copper vented versions, and some unvented cylinders are good, whilst others are not. Some will only transfer about 10kW, but others can handle 70kW.

It is the ability to heat water at a good rate that matters.

 

[Schmill]

So presumably I need to;

- Determine the heat output of my boiler, (presumably the best I can do is find out what it did when it was NEW, and allow for the fact that it's now likely less than that?)
- Find out the transfer rating of the coil in the cylinder

I'm presuming there is little point in getting a cylinder with a transfer rate much higher than the boiler can give?
Also most places don't seem to quote ANY transfer rate for the coil in the cylinder, how do I find this out?

Lastly, if I know that I would need 250L of 'stored' hot water, how do I work out what size of 'fast recovery' cylinder I would need?

Thanks, sorry for all the questions but I am keen to learn as much as I can