Central Heating Schematic

[Smiler.]

Right, in need of a sanity check.

I have now found diagrams on the net showing almost every possible combination of vent & pump location for a typical 'S' plan setup (2 x 2-port valves, 1 for rads & 1 for hot water cylinder).

I have made a rig with the pump, 2-port valves & auto by-pass valve.




What I need to know is the best location for the top-up feed & vent pipe connections.


Should these both be before the pump on the feed side, or on the return side, or one on the feed & the other on the return?


I'm not looking to connect anything yet, I have a plumber who will commission the system & make all the final connections once the arrangement has been approved.


Also, what are the rules governing the minimum distance (length of pipe for the feed/vent connection from the boiler?


Indebted as always

[Gingerbread Man]

On the flow between the boiler and the pump. You could combine the feed and vent into one pipe to reduce chances of the pump sucking in air.

[Smiler.]

Gingerbread Man said:

On the flow between the boiler and the pump. You could combine the feed and vent into one pipe to reduce chances of the pump sucking in air.

So make a T off at the header tank end?

[ferg]

The vent and cold feed MUST be on the inlet side of the pump. Vent first, then cold feed. These MUST be within 150mm of each other. You can put a combined cold feed/vent in in 22mm, BUT ONLY if the boiler has a high limit thermostat (which most, if not all do now).

[Smiler.]

ferg said:

The vent and cold feed MUST be on the inlet side of the pump. Vent first, then cold feed. These MUST be within 150mm of each other. You can put a combined cold feed/vent in in 22mm, BUT ONLY if the boiler has a high limit thermostat (which most, if not all do now).

Thanks Ferg. The boiler is quite old (10 years poss) - how can I tell if it has a hight limit stat?

[ferg]

Smiler. said:

ferg said:

The vent and cold feed MUST be on the inlet side of the pump. Vent first, then cold feed. These MUST be within 150mm of each other. You can put a combined cold feed/vent in in 22mm, BUT ONLY if the boiler has a high limit thermostat (which most, if not all do now).

Thanks Ferg. The boiler is quite old (10 years poss) - how can I tell if it has a hight limit stat?

Tell me what make it is, that's probably safest. If it has a small red re-set button (as seen on another thread here yesterday or the day before) it has, but it also might have one built into the software/PCB...

[Smiler.]

ferg said:

Smiler. said:

ferg said:

The vent and cold feed MUST be on the inlet side of the pump. Vent first, then cold feed. These MUST be within 150mm of each other. You can put a combined cold feed/vent in in 22mm, BUT ONLY if the boiler has a high limit thermostat (which most, if not all do now).

Thanks Ferg. The boiler is quite old (10 years poss) - how can I tell if it has a hight limit stat?

Tell me what make it is, that's probably safest. If it has a small red re-set button (as seen on another thread here yesterday or the day before) it has, but it also might have one built into the software/PCB...

It's an Ideal Classic FF280

Edit: It does have a red reset button (Overheat Stat) - is this what you mean?

Edited by Smiler. on Saturday 27th November 14:35

[ferg]

Smiler. said:

ferg said:

Smiler. said:

ferg said:

The vent and cold feed MUST be on the inlet side of the pump. Vent first, then cold feed. These MUST be within 150mm of each other. You can put a combined cold feed/vent in in 22mm, BUT ONLY if the boiler has a high limit thermostat (which most, if not all do now).

Thanks Ferg. The boiler is quite old (10 years poss) - how can I tell if it has a hight limit stat?

Tell me what make it is, that's probably safest. If it has a small red re-set button (as seen on another thread here yesterday or the day before) it has, but it also might have one built into the software/PCB...

It's an Ideal Classic FF280

Edit: It does have a red reset button (Overheat Stat) - is this what you mean?

That's it.

How much of the system is new? If it's a major repipe you might consider sealing the system.... No fear of pump-over then. Just a thought.

[Paul Drawmer]

ferg said:

How much of the system is new? If it's a major repipe you might consider sealing the system.... No fear of pump-over then. Just a thought.

Result! I was thinking that; and the Fergmeister said it!

[Smiler.]

It's all re-piped apart from the drop to the boiler.

What's involved in sealing the system?

Does that mean I don't need a header tank?

[Gingerbread Man]

Smiler. said:

It's all re-piped apart from the drop to the boiler.

What's involved in sealing the system?

Does that mean I don't need a header tank?

Header tank out and an expasion vessel put in.

Any dodgy joints will become apparent with a pressurised system. It is a better setup though.

[Smiler.]

Update:

This is the schematic for my boiler




This is not what was previously installed, so can I run a 22mm pipe to the cistern, tee off for the vent before the output valve on the tank as previously discussed?

[ferg]

I've never seen a diagram like that before!! NRV??

Where's the expansion??

[Gingerbread Man]

ferg said:

Where's the expansion??

Pissing out a joint.

[Smiler.]

I think they haven't shown the vent.

Am I ok to run the combined feed/vent as previously suggested?

[Gingerbread Man]

Smiler. said:

I think they haven't shown the vent.

Am I ok to run the combined feed/vent as previously suggested?

Leave the non-return valves out of it, and definitely don't put any sort of valve/ restriction on the vent.

Combined feed and vent if you can if it's open vented. An unvented system is better though.

[Paul Drawmer]

O/P, where did that diagram come from?

[Smiler.]

Paul Drawmer said:

O/P, where did that diagram come from?

From the boiler instructions.

This is the one for the vented system




I can't quite make out the dimensions shown. Does the diagram require:

a. The minimum head from the top of the boiler = 1500mm
b. The min head from the highest point = 450mm


I've been advised to keep the level in the header tank to 3 inches (can't remember why though).


Also, why must the vent be on the return? Would it not be better on the flow?


Cheers again chaps

[ferg]

Right.

I'm confused!! LOL!!

You've got this rigged up to a cylinder via a two-port valve and it's a combination boiler????

[Smiler.]

Right, having now got a hold of the CORRECT manual.......




Which I thinks is what you said further up the thread.