CH with Microbore bypass loops and proper bypass valve

[Rob1234]

Hi - and thanks in advance for reading - just joined...

I have been looking into why my heating takes ages to warm up - had the system power flushed and lots of things checked... Today, I found this:

This is one of 4 manifold pairs - and it also feeds the worst of the radiators for not warming up.. Is it correct or normal to have the two loops from flow to return like this?

The bypass loops are (predictably) lovely and (ouch) hot - the feed to the rad gets hot-ish after a while and the return from the rad barely warms up at all, this is with the stop valve on the rad open and the TRV removed. The radiator has ben taken off and flushed out with a hose as well.

Is this in any way normal practice? Can I fit 4 blanking plugs and rely on the bypass pressure relief valve? - It is marked from 0.1 to 0.5 bar, any good starting point for settings would be appreciated!

FYI, 15 rads in all on Viessmann 100-W 19KW boiler, house built 2002

Thanks for reading - any ideas and info much appreciated

 

[John.g]

What setting is the ABV (bypass) set to now and where is it located?, ie close to the boiler or at the other end.
When the rads are cold, and after the boiler fires up, just shut that by pass (setting 0.5) and see do the flow&return pipes heat up faster/better. Also ensure the ABV piping goes cool/cold, it may be leaking past.
When the ABV outlet pipe cools down, very slowly reduce the setting until you just feel the pipe getting warm (this may happen at ~ 0.3 to 0.4 setting) and then turn the adjusting knob back (clockwise?) down by approx a 1/4 to 1/2 a turn, this should reclose the ABV which will/should reopen when TRVs, if fitted, close in, or zones shut off or the boiler shuts down, You will have to tune this over a period but should get it reasonably right after a while. Unfortunately, quite a lot of circulating pumps now operate in a mode that makes it difficult to get a proper setting.

 

[Rob1234]

Hi John, thanks for the quick reply - Boiler is in garage, quite a way from the ABV in airing cupboard near the 2 zone valves (water and CH)

Any thoughts on the bypass loops in the photo?

 

[John.g]

No, I have never seen this type of manifold, presume these by pass loops are separate from the ABV which is normally installed between the (main) flow & return piping so don't know what these others are for except that the ABV has control?, if it has then they will get cool when its shut.

 

[Rob1234]

These bypass loop are always hot if the boiler is running - they are directly between the feed and return and obviously a much easier route for the water than going round the much longer microbore to the rads as well as rads and TRVs along the way...

 

[ShaunCorbs]

Need to remove them loops / short circuits

 

[Rob1234]

Hi Shaun - Thanks for that, I was looking for some reassurance that they are not needed - or just plain wrong... They have been in place since the house was built, I would say - I had to make a new access hole in the floor to get to them...

When I moved in, it was a Y-plan setup and there was a simple gate valve as another bypass, I had it changed to S-Plan with an ABV.

Thanks for the info on New year - and a Saturday as well - now I just need to find the blanking plugs on a bank holiday weekend...

Anyone around Coventry who I can cross your palm, please shout

 

[ShaunCorbs]

Screwfix

Worst comes to the worst 10mm push fit cap ends and inserts

 

[John.g]

Hi Shaun - Thanks for that, I was looking for some reassurance that they are not needed - or just plain wrong... They have been in place since the house was built, I would say - I had to make a new access hole in the floor to get to them...

When I moved in, it was a Y-plan setup and there was a simple gate valve as another bypass, I had it changed to S-Plan with an ABV.

Thanks for the info on New year - and a Saturday as well - now I just need to find the blanking plugs on a bank holiday weekend...

Anyone around Coventry who I can cross your palm, please shout

Would like to know the rationale behind those uncontrolled bypasses.

Would also suggest installing a 22mm gate/lever valve in series with the ABV as you will achieve more control due to the circ pump mode, you could consider doing it in conjunction with the above as your system will be drained/partially drained down anyhow.

 

[Rob1234]

Would like to know the rationale behind those uncontrolled bypasses.

Would also suggest installing a 22mm gate/lever valve in series with the ABV as you will achieve more control due to the circ pump mode, you could consider doing it in conjunction with the above as your system will be drained/partially drained down anyhow.

Hi John, thanks for that - that is exactly what I have actually got now - there was a ABV that was letting some water through all the time, regardless of setting - so I got it changed and a gate valve added...

When I moved in, there were two bypass radiators (no trv), a simple gate valve for bypass and those two loops in the photo... I think someone was not really understanding how it should work...

Mind you - there were fluorescent lights under the kitchen cupboards behind wooden plinth strips as well...

I know you don't believe me so here you go:

And yes, they were wired and working when the lights under the top cupboards were turned on...

 

[John.g]

What make of ABV is installed now?.

 

[Rob1234]

Not sure what make it is...
But - stop ends fitted and I now have 20-25C drop on the return - It was 10-12C before BUT the boiler is sitting at 26% modulation with 72C flow, 51C return and still not getting much flow it seems...

Thanks for help and advice everyone and kudos for screwfix being open today - I think I need to start a new appropriate topic for the boiler!

 

[Rob1234]

Screwfix

Worst comes to the worst 10mm push fit cap ends and inserts

Thanks Shaun - Screwfix were open today, it was not apparent from their web site - and yes, push fit caps and inserts was the way to go, I figured not messing with the 19 year old manifold connections was preferable...

 

[John.g]

Not sure what make it is...
But - stop ends fitted and I now have 20-25C drop on the return - It was 10-12C before BUT the boiler is sitting at 26% modulation with 72C flow, 51C return and still not getting much flow it seems...

Thanks for help and advice everyone and kudos for screwfix being open today - I think I need to start a new appropriate topic for the boiler!

If the boiler is at 26% output then only running at 4.94kw and a flowrate of 3.37LPM!! If that is correct then something seriously amiss. Is the DHW cylinder heat up time OK.

 

[ShaunCorbs]

10mm gets blocked very easily sounds like you need to start looking at maybe a blockage at the inserts