expansion pipe

[lost_cause]

Sorry if this has been covered before - perhaps you could direct me to the item if it has.
What is the point of the expansion pipe (in the primary side) which feeds back into the header tank? Surely pressure can't build up in the system any where because there is always a path to the header tank through the feed pipe.
I'm asking because i changed my system from gravity to fully pumped and water is flowing back through the expansion pipe into the tank.
Also there was a pressure relief valve in the gravity feed side which i taken out - is that a problem?
Thanks.

 

[hi-spec plumbing heating]

>pressure can't build up in the system any where because there is always a path to the header tank through the feed pipe.

is there ?
a feed pipe is 15mm , vent pipe is 22mm min.
you can have a combined feed/vent 22mm min you can't use a 15mm feed as a combined.

>water is flowing back through the expansion pipe into the tank.

you have connected it up wrong the.

what order have you connected the pipes ?

return from rads, tank, boiler etc

 

[corgiman]

always nice to see people asking if that are right AFTER they have done the work



And your expansion pipe is the systems saftey valve and will blow if there is over heating in the system

the Pressure relief valve you removed is there in case the expansion gets blocked, not the best idea to move it

 

[lost_cause]

There was an old wall flame boiler, gravity feed hot water with 28mm pipes into the top and bottom on one side of the boiler water jacket.
The other side of the boiler had a 15 mm feed and return to the rads. There was a pump in the rad return.

I've changed the boiler and now puimp the feed. ther is a 22mm pipe from the top boiler feed going to a pump, then to a valve which switches between the old 15mm to the rads, and the old 28mm to the cylinder coil. The returns from the cylinder and rads are joined and go to the bottom boiler return. The other side of the boiler is blanked off.
the expansion pipe goes from the top of the hot water cylinder coil up into the roof ridge of the bugalow and into the top of the header tank.
the feed from the header tank is 15mm and joins the 28mm at the bottom of the cylinder coil.
When the pump is powered and the valve set to hot water there is a steady flow from the expansion pipe into the header tank.
Is there a simple fix?
Ta

 

[oakland99]

you've piped the vent and feed wrong you've left it like the old gravity system this wont work on fully pumped, feed and vent needs to be on flow pipe before pump and valve you can either do an H configuration or combined feed and vent. check M/Is for info

 

[gas4you]

Your f&e tank is being treated as another radiator.

The 22mm flow from the boiler will probably go to the airing cupboard and should rise in there.

About 3/4 up the wall Tee off in 22mm and the rising pipe will be the open vent.

Run this T off for about 100mm then T again, the rising pipe off this is the cold feed, often 15mm, but preferably 22mm these days. The cold fill gate valve will be in this rising pipe.

The bottom of the T will then have the pump attached as close as possible.

After the pump will be the auto bypass valve, then either the 3 way valve or a T to the 2 2 port valves.

Hope this is clear

 

[oakland99]

Your f&e tank is being treated as another radiator.

The 22mm flow from the boiler will probably go to the airing cupboard and should rise in there.

About 3/4 up the wall Tee off in 22mm and the rising pipe will be the open vent.

Run this T off for about 100mm then T again, the rising pipe off this is the cold feed, often 15mm, but preferably 22mm these days. The cold fill gate valve will be in this rising pipe.

The bottom of the T will then have the pump attached as close as possible.

After the pump will be the auto bypass valve, then either the 3 way valve or a T to the 2 2 port valves.

Hope this is clear [

didnt i just say that

 

[gas4you]

Yes you did, but it wasn't there when I started typing it out

 

[oakland99]

its a case of great minds think alike