Moving feed and expansion

[bcafg1]

Working on a loft job where the cw cistern and feed and expansion tanks need moving about three feet higher and slightly to one side. Is it a case of turning the incoming supply off, draining the ch system and cw cistern.

 

[Beans-on-Toast]

With all due respect,

If you are 'Doing A Job' and you don't know what to do, where does that leave the owner.....?

 

[Fluffster]

More or less however there are regs that u must have a 350mm gap above or 500mm for a cws with a bolted on lid with 1000 litre capacity.
Make sure you raise both evenly as this may cause the vent pipe to pump over.
Better still get a plumber in so you have a guarantee it is sorted.
Pete

 

[Bamber gaspipe]

Don`t forget to post back when your F&E fills up but when you attempt to bleed your radiators.......... only joshing.. Good luck!

 

[bcafg1]

Thanks for the advice. Weve already built a frame for the cisterns and knew about the 350mm gap. The tanks will be lifted the same heights. I cant see a problem with it myself, extending the pipework 3 feet. Out of interest why would the vent pipe pump over. Is it if the cw cistern is placed higher(than it currently is in relevance to the f&e) than the f&e tank?

 

[Fluffster]

Exactly mate more head of pressure pushing the water up f/e pipe.
Good luck
Pete
ps do not be tempted on putting a service valve on the f/e feed as this also acts as an expansion pipe.

 

[bcafg1]

Thanks for the help Fluffster. Much obliged

 

[Nige F]

Saved £400.oo that`s what someone charged to move one cold cistern ....and it wasn`t BG

 

[bster]

There is a calculation you can use to ensure that it wont pump over something like 40mm per meter satic head plus 150mm (for CWST measure from base of cylinder to water level) i dont think the F&E tank can be included using this calc but someone will surely tell us.

And make sure there is an air gap between the probable water level when hot and the end of the vent pipe.

 

[Nige F]

There is a calculation you can use to ensure that it wont pump over something like 40mm per meter static head plus 150mm (for CWST measure from base of cylinder to water level) i dont think the F&E tank can be included using this calc but someone will surely tell us.

And make sure there is an air gap between the probable water level when hot and the end of the vent pipe.

You`re confusing the DHW and the F+E the heating pipework should........(and that`s a big should , given the number of systems I`ve seen over the years )be laid out so there is no pressure/vacuum acting in the cold feed or vent pipes....that`s where the neutral point/ >150mm gap between cf and vent comes in .This principle has been b`stard ised into the H layout as used by BG and many others who can`t afford a Myson Airjec and don`t know how to orientate it anyhow.......Glow-Worm did a specific layout for using a low head from the f+e with their wall hung boilers way back........anyone got details?..........used to do them and wondered WTF the boss wouldn`t go for sealed system PS water Regs say both cisterns should be on same level base

 

[bster]

Nige F

Why do you say i'm confusing the CWST (DHW) and the F&E (CH)?

Are you saying if you arrange the vent and cold feed the required 150mm behind the pump blah bla blah.... it will not pump over even if the vent terminates as low as poss?

 

[Gasguru]

The flow pipe from the boiler runs to the pump. On this pipe run the feed pipe is kept within 150mm of the vent pipe (vent pipe comes first). It doesn't really matter how far this is behind the pump.

This way the pressure difference between the feed and vent is negligable (and there is little chance of pumping over) and is termed the neutral point.

The pressure between the feed/vent to the pump is negative, and the pressure after the pump and back to the feed/vent is positive, helping to reduce the chance of air ingress on the system.

This setup is known as a close coupled feed and vent and is commonly seen as the H pattern in airing cupboards. It is a cheaper way than using an air seperator such as an Aerjec or similar.

 

[bster]

Gas guru -

If you were replying to my post.. I already understand the feed\vent\pump relationship and how to pipe but how high above the F&E does the vent pipe have to be (not the outlet but the highest point) or are you saying that if it is piped correctly (using the close coupled method or an air separater) it does not matter?

 

[Nige F]

Nige F

Why do you say i'm confusing the CWST (DHW) and the F&E (CH)?

Are you saying if you arrange the vent and cold feed the required 150mm behind the pump blah bla blah.... it will not pump over even if the vent terminates as low as poss?

Vent+c/f should be less than 150mmbetween each other....posn. from them to pump is not critical..somewhere I read that H is , as I said a b`stardised version of what was originally both Feed and Vent rising off a horizontal pipe ..then some one said the feed should tuck under and enter from below....then the H appeared ........As I read it your measurement refers to the vent on the DHW cyl. which is not under any pumping force, but it reads like you are saying it is Not a critisism, but when writing technical explanations, you need to double check how they "read"...

 

[bster]

Sorry about that Nige - as you can tell I am constantly trying to learn but at the mo i'm overloading- there is so much to learn!!!!!!!!!!!!!!!

still love the job though!