auto bypass valve required and location

[ninjanik]

Hi guys.. i'm after a little advice / guidance with regarding the need for an auto bypass valve.

The current system was installed by myself aprox 7/8 years ago under the guidance of a local gas fitter - who also installed and commissioned the boiler.

Back to back terrace 42 m2 total floor space:
Biasi Garde HE Combi (Condensing - B-rated (got it fitted just before the regs outlawed B rating))
6 rads - 5 trv's
Programmable room stat - situated in on the top landing - 2 rads on stairs - 1 at the top with trv - one at the bottom without trv (open lock shield)

I'm replacing the bathroom rad with a large towel rad - and therefore removing the trv (because they don't match the new rad and I want this one to be on so it drys the towels etc)
The balancing of the system means its quite noisy (water velocity - against the lock shields etc - only a small system - boiler slightly over sized etc)

This got me thinking if I need an external bypass valve - whilst i'll have the system drained etc.
The boiler instructions clear state it has an internal ABV fitted - but it then caveats this by saying an external one may be required
I've emailed biasi - and their response was useless - missing the point about the ambiguity - and stating 1 rad should not have trv (from what i understand this is now not allowed in new installations ?)

The only places available to fit an external ABV would be either directly after the boiler (before any rads) or right at the end of the flow / return loop (which is where the rad with no trv currently is)

So my questions are:
Do I need an external ABV - or leave as is
If so where in the loop should it be fitted (begining / end)

Sorry for the long post.. any advice appreciated

cheers Nick

 

[AWheating]

no you dont need an external bypass valve as you have a radiator that is never turned off and a internal one for back up.

if you did want to fit one it needs to be a few meters of pipework away from the boiler across the flow and return in an accessible position for adjustment. ie. above boiler, under bath, in cupboard etc....

 

[johnnyplumb]

you should'nt need an external bypass, radiator with lockshields and boiler internal bypass should be fine,
however , check what biasi say in there installation instructions,
the ideal logic installation instructions state that any radiator used for a bypass should be of a size that is at least 10% of the minimum boiler output.

 

[ninjanik]

Ok guys... thanks for the responses.

I'd read that it was no longer regulation to leave 1 rad open for bypass on new installations? - I do a lot of work myself (where legal) and if making changes i try to do these to any current regs to the best of my knowledge... hence my questions

Biasi have been useless... There installation instructions are ambiguous.. so I emailed them yesterday asking them to clarify.. their response was just as vague, didn't clarify when an external one would be required (i.e. when the internal one wouldn't be sufficient.. as stated in the instructions)

I'll leave things as they are... since with changing the bathroom towel rad to manual valves - the system will have 2 rads open (1 permanently)

cheers Nick

 

[AWheating]

the regs require a room stat which requires a non trv controled rad = bypass.

 

[ninjanik]

the regs require a room stat which requires a non trv controled rad = bypass.

That was my original understanding.. I think i've confused myself reading different things on different forums, where they talk about electronically controlled trv's and bypasses etc, Y plan / S Plan etc etc ... and got thinks slightly confused in my head lol... that and the fact that in recent years the building regs seem to constantly change every year

Always good to ask

cheers Nick

 

[AWheating]

they are currently going throught the motions to change part L again in next year or two, the zoning change was a total stupid idea really and i cant imagine what the next stupid idea will be.

 

[DirksPlumbing]

Back to back terrace 42 m2 total floor space:
Biasi Garde HE Combi (Condensing - B-rated (got it fitted just before the regs outlawed B rating))

I do not know if that is good news for you but Band B has not been outlawed it has just been renamed Band A and tightened up.