New TRVs not working as expected

[Spud1]

Hi,

I recently had new radiators installed with new Drayton RT212 TRVs. (Also new boiler etc) Since the plumber has left we have found that most of the radiators won't heat up at all unless they are set to 5 or 6 despite the room being cold. I'm an electrician so I know that everything is working control wise. It's definetly something to do with the TRVs. Are they adjustable other than the normal user adjustment? Does this sound like the system isn't balanced properly?

Thanks!

 

[John.g]

The actuators should be set fully open at setting 6 before attaching them to the TRVs otherwise you are trying to push in the pin while tightening them, most TRVs only need settings of 2 to 3.0 to give a normal spread of control.

 

[ShaunCorbs]

Are they on the flow pipe also should be the hottest pipe

 

[townfanjon]

As above from Shaun , is the pipe hot at the trv?
Longshot .. have you got weather compensation?

 

[Chuck]

Are they adjustable other than the normal user adjustment?

Yes. Firstly, they have both a 'fully-open impedance' adjustment, which can be used instead of the traditional lockshield adjustment. Secondly the mapping of the 1-6 scale to 'temperature' can be adjusted. Drayton's commissioning guide explains the details. You need a special 'key', which is available from merchants.

The installer should have set them up as part of the benchmarking process.

 

[John.g]

The actuators should be set fully open at setting 6 before attaching them

Are they on the flow pipe also should be the hottest pipe

That has been mentioned by several installers on here, my own experience is that I have always installed them horizontally on the return because I think that they are sensing a more representative room temperature, of course by doing this the flow is the same way as installing them vertically on the flow end, ie the flow is from under the valve seat, they have worked perfectly in this position but may not if installed in the vertical on the return.
I did take flow readings from both a new bi directional TRV and its accompanying lock shield valve and got the same readings of 3.8 LPM @ 0.5M head in both directions on both which corresponds to the manufacturers flow rate (Kvs) of 1 M3/hr @ 1 Bar head.

 

[Scott_D]

Put them all on max and crank the heating up.
Do all radiators get hot?

 

[siricosm]

I would crank them all to max and balance the system.

 

[John.g]

Hi,

I recently had new radiators installed with new Drayton RT212 TRVs. (Also new boiler etc) Since the plumber has left we have found that most of the radiators won't heat up at all unless they are set to 5 or 6 despite the room being cold. I'm an electrician so I know that everything is working control wise. It's definetly something to do with the TRVs. Are they adjustable other than the normal user adjustment? Does this sound like the system isn't balanced properly?

Thanks!

If the rads are heating up fully with the TRV almost fully opened then its hard to avoid the conclusion that there is something amiss if the actuators have been properly attached as there doesn't appear to be any special tools required (as per these instructions at any rate) to set them up, they do have a temperature limiting peg which my old mysons had 15 years ago but not as precise.
All TRVs have a very small temperature hysteresis of a degree or two so unless your rooms were very hot then the TRV should go fully open well before setting 5 or 6, setting 2 ~= 15C, 3 = 18C, 4 = 22C so IMO setting 3 or so should have called for full opening. I generally blow through them before installation while slowly opening the actuator, this gives a good idea of the index for that particular room temp.