mystery pipe

[drollord]

Please see diagram.
Can anyone explain what the red pipe and valve are for please?
Should the red gate valve be closed or open?

thanks
Mick

 

[mutley racers]

its an old skool bypass valve. Which should be opened a little bit. it is there so the heat doesnt stay in boiler when demand for heat stops. When demand stops, the pump runs for roughly 10minutes after and the pressure will force the heat pass this gate valve.

 

[drollord]

its an old skool bypass valve. Which should be opened a little bit. it is there so the heat doesnt stay in boiler when demand for heat stops. When demand stops, the pump runs for roughly 10minutes after and the pressure will force the heat pass this gate valve.

thanks mutley, the valve was/is open half a turn. it was all fitted by an old fellow a few years ago who must have gone to a very old skool :lol:

 

[jtsplumbing]

Not that old a system, just shows how much you young chaps dont know, this is quite a common way to do a bypass sometimes you will find a service valve (Ball-o-Fix) not every system is a combi, do you not cover this in college ? sorry i am one of these old fellows, who went to the old school, sorry i better spell that skool or you wont understand what i mean.

 

[migoplumber]

as above, really nice drawings tho !

 

[M77]

System wouldn't really need a bypass though being a 'y plan' ??

 

[mutley racers]

Confusing isnt it with the Y plan

 

[AlexGas]

Not sure about the gate valve by the cylinder!?

 

[dancinplumba]

Not sure about the gate valve by the cylinder!?

isnt that for balancing ?

 

[dancinplumba]

System wouldn't really need a bypass though being a 'y plan' ??

what happens when only calling for hot water ? some through coil and rest through by pass ?

 

[dancinplumba]

thats why by pass valve connects to cylinder return

 

[AWheating]

its a bypass and is now against the regulations to fit them that way and should have an automatic valve, but you do still see them fitted. They do there job, best not to touch it unless your balancing your system again

 

[M77]

No need for a bypass as there's always an open circuit. Maybe if the cylinders throttled right down I suppose, but it would have to be nearly shut!

 

[AWheating]

Confusing isnt it with the Y plan

pretty standard fair to fit with a yplan, especially in HA and council propertys. Is it needed? well if the 3 port valve sticks under fault with the hot water closed then i guess so.

 

[dancinplumba]

No need for a bypass as there's always an open circuit.

yes but when coil throttled back rest has to go somewhere, thro by pass

 

[AWheating]

i would say its good practice to.

i fitted a new cylinder,tank and y plan today and it has had a bypass. Council spec.

 

[R1CKY]

No need for a bypass as there's always an open circuit.

Unless there is only CH demand and the TRVs are all closed.

 

[chris watkins]

Seems to be a general mis-understanding of what a by-pass is for (both reasons) & what is required under Part L & why this is so important for condensing boilers.
Could someone not give a definitive answer, please ?

 

[M77]

Yeah but how throttled down you talking. And what ever position the valve sticks on there's still open circuit.

 

[R1CKY]

An auto bypass, in my understanding is there to stop "dead head" (pumping against a dead circuit) and more importantly to keep flow rates up through low water content heat exchangers to prevent terminal damage.

 

[M77]

Always took it as bypass was for pump over run and to take any load off pump/boiler as valve/trvs shut down.

 

[dancinplumba]

Yeah but how throttled down you talking. And what ever position the valve sticks on there's still open circuit.

enough to get temp drop

 

[R1CKY]

Yeah but how throttled down you talking. And what ever position the valve sticks on there's still open circuit.

There isn't an open circuit if there is only CH calling and all of the TRVs have closed.

 

[AWheating]

keep condensing boilers condensing longer, save/use's all energy.

 

[M77]

But yeah you would need a rad on lock shields

 

[dancinplumba]

but, is rad big enough ?

 

[drollord]

Unless there is only CH demand and the TRVs are all closed.

There are eight radiators, only three upstairs (bedrooms) have TVR's

 

[R1CKY]

Bloody big bedrooms if they can fit TVRs in them.......

On a serious note, whilst in your example there may only be three. You'll quite often find houses have TRVs on every rad, if they are all up to temperature, the valves will be closed, so the pump is pumping away at a brick wall effectively, this is why bypasses are fitted, to prevent this from happening. Pump against nothing will cause premature pump wear, cause boiler overheat and possibly cause terminal damage to the boilers heat exchanger.

 

[M77]

enough to get temp drop

Just to get a temp drop, so no need for it to go through bypass.

 

[dancinplumba]

Just to get a temp drop, so no need for it to go through bypass.

temp drop thro coil not boiler