Sundial Y v Sundial S

[kevplumb]

Lads, this valve lark is causing me some consternation, so I've done a bit of research on the internet. It seems the ABV is needed when a CH system is fitted with TRV's in order to maintain flow through the boiler when the TRV's shut down.

What is this mysterious research, and why does it fly in the face of common sense?

The flow to each rad connects to the flow from the boiler, and the return from each rad joins the return to the boiler, so opening a rad valve doesn't affect the resistance of the distribution pipework, other than to introduce turbulence.

Why do you think that shutting a TRV, or any rad valve, will impede the flow through the distribution pipework?

pure tosh

 

[DIYedboy]

Fair enough Kev, no TRV's = no ABV

 

[kevplumb]

sounds like a plan fella

 

[Goldberg]

no TRV's = no ABV

That's a pity, because you were so close to understanding.

 

[kevplumb]

what any of the tosh you decided to post on the thread

you have to be joking

 

[bengasman]

... My house don't have any TRV's (thank god)..........................can I hold my head up high and dismiss the need to fit an ABV?

In a word: no.

 

[DIYedboy]

Eeerrr...................Bengas..............why not?

 

[kevplumb]

part l building regs

shhhhh

you are supposed to fit them

 

[bengasman]

Eeerrr...................Bengas..............why not?

Leaving aside the regs for a moment, the technical reason is that you need to create a way for the boiler to dissipate the heat when a combination of mv's and/or rad valves have closed the normal flow.

 

[DIYedboy]

Kev............them flamin regs get everywhere don't they?.......sshhh who said that?

Bengas.............Thanks very much for answering that,at last I think I have the full picture: so if the CH is on and the roomstat says I'm hot enough, it cuts the voltage to my 2port MV which then closes and opens the microswitch which cuts the boiler out and starts the pump overrun, this is the same situation as all TRV's being shut. The water in the water jacket therefore can't go anywhere and gets hotter n hotter which is why the bypass is necessary to let the water into the return pipe and create a temporary flow to cool it down thanks to the pump overrun..............is this right?

 

[bengasman]

Close enough; there are other possibilities that could lead to the boiler not dissipating the heat, but the principles remain the same.

 

[Goldberg]

if the CH is on and the roomstat says I'm hot enough, it cuts the voltage to my 2port MV which then closes and opens the microswitch which cuts the boiler out and starts the pump overrun

Correct.

this is the same situation as all TRV's being shut.

No - it's completely different to the TRVs being shut.

The water in the water jacket therefore can't go anywhere and gets hotter n hotter which is why the bypass is necessary to let the water into the return pipe and create a temporary flow to cool it down thanks to the pump overrun..............is this right?

That part is right, but it has no relationship to whether or not the TRVs are open or shut.

 

[kevplumb]

christ do you ever stop digging

 

[bengasman]

Diyedboy, have you been informed about the reliability of coldberk's statements?
Forgive him his rantings for the moment, he is a bit punchdrunk after scoring several enormous blunders today.
We are talking about:

Untitled

• bengasman
• 1 Nov 2009
• 1

this kind of stuff.

 

[DIYedboy]

To be honest, I have seen you boys ripping the guts out of poor old Goldberg in other posts, but your arguments get a bit too technical and I can't keep up with them