Radiator hot when call for HW not CH

[eddie twadds]

Moved into a brand new house with the following set up:

Potteton Promax HE
Twin zones (Zone 1 = bottom floor and Zone = top two floors) via Siemens controls
Big Kingspan HE cylinder and teeny tiny radiators (I'm used to living in older houses - LOL)

The radiator in the main bathroom which is adjacent to the airing cupboard (which houses the pump, expansion tanks and cylinder) doesn't have a TRV and comes on when there is a call for hot water. I can turn it off via the lock shield - but before I talk to the builder, all I really want to know is 'Should this happen? If pics of the install will help then I will post these.
Thanks

PS I have also had to bleed the top floor rads on two separate occasions - is it usual to have trapped air in brand new systems or should this have been sorted by the installer?

 

[crockett]

Eddie the reason for this is that the towel rail pipework is linked to the primary, which some homebuilders prefer because the towel rail / rad will dry towels etc. quicker.
As for air in the system, you didn't say whether the system is gravity or sealed.

 

[eddie twadds]

Not gravity - fully pumped - with expansion vessels for HW and CH - so presume that means sealed?

 

[crockett]

right, well you said its a new property, so I would imagine that the system is 'settling in'. This can sometimes take days, weeks even, especially if the pipework layout is of a poor design!! you should have a pressure gauge on the central heating pipework somewhere, either on the boiler or where the filling loop is, and this should read between 1 - 1.5 bar. If you have to keep bleeding the system for days, you may have a leak somewhere, so check all visible pipework, look for damp patches, check for leaking fittings. If you have any pipework buried in walls or under the floor, this could also be a potential area for leaks.
Don't panic yet though!! I more than likely is settlement.

 

[eddie twadds]

I hope it is just settling-in - there are a lot of rooms and rads to investigate if there is a leak! (all for the builder to tackle though).

BTW - are plastic piped systems more prone to leaking than copper systems?

 

[crockett]

Not necessarily. Pastic is used a hell of a lot now, and, providing adequate alllowance for thermal expansion is designed in (!), using it is fine. I use plastic on occasion now, and have only ever had one joint fail on me, which was missing an 'o' ring. I now check EVERY new plastic push fitting !!
As for checking leaks, if you've got one it will soon show itself, unless its underfloor !
The builder will probably bleed them once for you, if you're lucky, but they will then expect you to continue doing it........

 

[eddie twadds]

Thanks for the advice - hopefully it'll settle down - just like the rest of house