new rads not working

[Plumbgjc]

hi all, got a really irrittating problem with 2 new large tall column rads that I've installed onto an existing system - combi boiler vaillant 30kw. The problem is they don't heat up the rest of the rads on system work fine including a small column rad in the same room as these two! if I turn all other rads off in house I can get one to work perfectly and the other gets fairly warm but it's not right! so this proves the valves and pipe work are ok! There are 17 rads in total on system could it be the boiler is undersized?

any help would be great!

 

[JohnD]

you forgot to say if they were replacement rads fitted to existing pipework and the same size as the old ones, or not.

Look at "radiator balancing" in Wiki or FAQs

//www.diynot.com/forums/viewforum.php?f=7

 

[Agile]

Boiler is fine!

It sounds as if you have added them both onto 15 mm pipework going to an existing rad.

Apply Kirchoff's laws!

Tony

 

[Plumbgjc]

hi tony they are on 15mm pipework but it comes directly off 22mm and one run just feeds the smaller column the other is the first on the run for main house! they are all the first rads in system!

 

[Agile]

If each one is individually directly fed with 15 mm from the 22 mm then that is fine.

Clearly something is seriously wrong. Are you sure you read the makers instructions?

Tony

 

[Plumbgjc]

never saw any MI customer ordered rads...the large ones are 6000btu and small 3000btu! there is the smaller one and one of the larger ones fed from one 15mm run and the other is on its own run! so there's max 10000-11000 btu on the larger including the pipe run! so cant be a prob with pipe sizing can it?

 

[Agile]

That does sound risky! Two rads on 15 mm can be chancy!

But can probably be solved by balancing.

Many of these coluum rads have internal baffles which need to be positioned correctly.

Tony

 

[Plumbgjc]

do you think I always worked to 10,000-12,000btu on 15 mm never had an issue! The problem on the new pipework I've put ie the one of the large and smaller column rads is sorted now piping hot the brand new trv was restricting the flow too much works fine with no head on it...weird, anyone aware of anything about trvs not working with tall large column rads?

The other large column will only get like warm without the trv head, this is on original pipework and I think is on a one pipesystem prehaps, which would def not work with this rad on 15mm! what do you guys think?