installing two indirect hot water cylinders

[caveyuk]

Hello!

I wonder if someone could give me some advice on an installation please.
Basicly, i plan to install a twin impeller pump to power a bathroom which has whb, bath and mixer shower.
I live in a bungalow and the cold water storage tank and hot water cylinder are both stored in the eaves space. The cold tank sit on a shelf above the hot cylinder.
I would like to upgrade both the cold tank and hot cylinder to larger ones. The cold tank is not a problem but the hot cylinder is as if i install a larger one the top of it will will be above the outlet of the cold tank and i would think this would cause problems.
Therefore i am wondering if i can install two cylinders of the same size and join them together. Has anyone had any experience in doing this or would this just not work?
I have drawn a diagram of what i propose and would like some comments please.
Would the hot water draw off of both cylinders be equal and would they fill at an equal rate also? Would i need a boiler upgrade also maybe?

An image of what i propose is here



Thank you for your time and i look forward to hearing your comments please.
Seems a great idea in theory but i have no idea whether it would work!!

Regards

Adrian

 

[kevplumb]

don't run the cylinder coils in series

 

[gas4you]

How about a single larger unvented cylinder. No need for pumps then

 

[caveyuk]

thanks kevplumb, so it is possible then. So would i just tee off from each flow and return to the coils then? or seperate flow and return for each from the boiler, rather than installing in series as i show.

Good idea with the unvented cylinder solution although i don't know too much about them and was hoping to plumb this all in myself.

 

[gas4you]

If you have good incoming water pressure 3 bar or more and a 22mm cold supply available to the unvented cylinder then no probs. I would get quote from local installer before making a decision.

Back to your first idea, kev is right, plumb them in separatley. You would need two 2 port zone valves and a stat on each cylinder otherwise both would heat when possibly only one need the heat

 

[corgiman]

why do need so much hot water

bet ya a dollar if you do add a cylinder you will have to upgrade the boiler, they eat up the btu's they do

why not waste some poor hard working plumbers time and say you need a quote then he can give you a experianced opinion and you can do it for butkiss.

I kid of course, if you know nowt about unvented cylinders I really doubt you are competant enough to undertake this rather tricky job so dont

 

[doitall]

The primary side has already been covered so over to the secondary side, You missed the open vent on your CAD Drawing, and when you add it you're plan will not work because it will suck in air.

The pump connections needs to be lower in the cylinder, somewhere around the word "Indirect".

In addition you need to get a cross flow through the cylinders, which you have in the drawing, The size of the cold feed needs to be the next size up from the cylinder connection E>G 28mm or 35mm.

 

[caveyuk]

so basicly it will not work then, i thought as much really
Although adding a common vent surely would not suck in air as the cylinder has a vent already.
I understand the feed from the cylinders to the pump will need to be of surrey flange type or the like.
Oh well maybe i should rethink my strategy or just install a pump and a larger cold water tank(currently only 48 litres) and see how it goes from there. I only wanted to upgrade the hot water storage so that we don't run out when using the shower, if we have a couple of showers in a row.

Thanks for the comments.

Adrian

 

[gas4you]

Have you thought of a single fast recovery cylinder? These re-heat the hot water very quickly. The 120 litre is designed for a two bath property. I fit these where ever I can on a traditional system and they work extremely well

 

[caveyuk]

Mmmm! I like the sound of that one. I will look into that for sure. Thanks for suggesting that.
My main problem being is if we use the bath and empty the cylinder we usually have to wait well over an hour before the water is up to temperature again so we can use shower or do a few dishes maybe.
I am working on the assumption that say the pump delivers approx 15litres/min at shower then the cylinder is going to be empty after about 8 mins or so. If the fast recovery cylinders are any good then i think that maybe the way to go on this.

 

[gas4you]

Fast recovery cylinder will re-heat in around 15 mins from cold, but usually on a fully pumped system they start as soon as hot water is drawn off.

Try Plumb Center centercyl 120 I believe it is called. Other makes/brands are available. Plumb Center has 5 year warranty.

Note can only be used on a fully pumped heating system

 

[caveyuk]

Well i have checked my boiler out and it is CF60 output 13.2kw as far as i can see. I think that will be man enough.
I will check out the model you recommend, and have will read more about it have been having a gander at the albion superduty one online.

 

[caveyuk]

When you say fully pumped heating system, the central heating has pump on it but i don't think when just the hot water is on that it has a pump on that. I am relatively new and not messed about with the central heating/hot water plumbing side at all really.
I know plenty about drainage/regulations though etc.. as been doing that for over ten years now doh!

 

[kevplumb]

and afore you lot start NO it's not one of mine

 

[caveyuk]

nice!
So thats a fully pumped system then! Thanks!