Height differential required between an F&E tank and a cylinder?

[PlumIt]

Trying to add a shower into a small bathroom, I'm looking at moving my hot water cylinder to the loft. Currently, I have a vented 200L cylinder (in the bathroom) with the principal source of heat being an Economy 7 setup, which gives adequate hot water for our needs. The cylinder also has an internal coil that tops up the water-heating capacity via a small boiler in our multi-fuel stove. There are two F&E tanks in the loft, one for household water storage and the other for the indirect system connected to the multi-fuel stove.

I believe that I could put an unvented cylinder in the loft and achieve the required pressure from the rising main supply. I'm guessing that I would need to disconnect my indirect system powered by the multi-fuel.

If I wanted to retain the indirect system then I could only do this with a vented cylinder in the loft. I assume that I would need to have a difference in height between the household water F&E tank and the cylinder. What would the difference in height be? Would this height also be true of the smaller F&E tank for the indirect system? From the floor of the loft to the apex I only have 1.38m to use.

If anyone could clarify things for me then I would be grateful!

 

[ShaunCorbs]

You would need 2.4m above the cylinder top to the bottom of the cold tank

For any decent amount of pressure 5m is 0.5 bar pressure

 

[PlumIt]

You would need 2.4m above the cylinder top to the bottom of the cold tank

For any decent amount of pressure 5m is 0.5 bar pressure

Thanks for your reply, Shaun. So an unvented main's pressurized system and uncoupling the indirect heat source is the only way forward?

 

[ShaunCorbs]

If you want the cylinder moving yes sorry

 

[Ben-gee]

I know of several systems where the bottom of the cws tank is merely inches above the top of the vented cylinder and they work just fine - think of a fortic tank for instance…..

These are electric only mind you. I don’t know about your multifuel set-up , but this could be disconnected.

 

[ShaunCorbs]

I know of several systems where the bottom of the cws tank is merely inches above the top of the vented cylinder and they work just fine - think of a fortic tank for instance…..

These are electric only mind you. I don’t know about your multifuel set-up , but this could be disconnected.

And they run a shower ?

 

[Basher]

If you can raise the cold water storage tank enough (don't need to do the heating F&E tank), there's a chance you could gain enough head for a passable shower, if you could get say 2.5m, preferably 3m between the surface of the water in the loft tank, and the shower nozzle, and use a shower mixer designed for low pressure and feed it from 22mm pipe.
You don't need to move the hot water cylinder, you can leave it where it is (unless of course you need the space for the shower!)

I have an old Aqualisa mixer shower which has good flow from a cw storage tank about 2.5 metres above, and the hw tank is lower than the shower and the other side of the house!!

 

[Devisham]

Why not just swap out the vented indirect cylinder for an unvented indirect cylinder if you are thinking of going over to unvented? Or is the shower install going to be where the cylinder is?

 

[Ben-gee]

And they run a shower ?

Yep. Cws to cylinder in loft is a few inches, but shower is down below so some are Mira excel and some coda pro, these both run ok(ish) at 0.15bar head if you run in 22mm copper.
But OP could add a pump and then any shower will run fine. So yes he can put cylinder in loft to make room and run his shower.

 

[PlumIt]

If you can raise the cold water storage tank enough (don't need to do the heating F&E tank), there's a chance you could gain enough head for a passable shower, if you could get say 2.5m, preferably 3m between the surface of the water in the loft tank, and the shower nozzle, and use a shower mixer designed for low pressure and feed it from 22mm pipe.
You don't need to move the hot water cylinder, you can leave it where it is (unless of course you need the space for the shower!)

I have an old Aqualisa mixer shower which has good flow from a cw storage tank about 2.5 metres above, and the hw tank is lower than the shower and the other side of the house!!

Thanks for your reply Basher. I played the raising of the height of the CWS tank card when I installed the system, I built a sturdy stand for it and it now sits near the apex of the loft with just enough room to lift the lid for any ball-valve maintenance. And, yes you are correct, I need the cylinder space for the shower!

Why not just swap out the vented indirect cylinder for an unvented indirect cylinder if you are thinking of going over to unvented? Or is the shower install going to be where the cylinder is?

....yup, the shower will only fit if I move the cylinder from the first floor to the loft. I'll take a look at an unvented system.