TRV sensor head faulty / want to change valve ...

[oliverwilliams]

My TRV is faulty - i have tried the following:

turning off all other rads, and leaving the cold rad open
unscrewing the TRV head and the pin is fine but
when the head was off the rad got hot!

so the trv sensor is faulty....
(probably the gas bellows have expanded and not contracted and when the head is screwed on, keep the pin pressed fully down).

so i want to change the trv - but

instead of draining down the whole system (open vented type) and then buying £15 inhibitor again on re-fill, i want to "bung the feed cistern cold feed and open vent pipes".

i believe and have heard some tank connector fittings do not allow "bungs" to fit snugly and allow a little air through, and therefore do not allow the vacuum to be created.

is this true? do some tank connector fittings not hold bungs tightly? and if so, is there any way around this to make sure they do hold?

also, when changing the trv, i will change the valve body and head but can the 2 original nuts and olives, both to the rad tail and 15mm diameter copper pipe be re-used again. Any tips to make sure they do create a watertight seal again? The reason i do not want to change the nuts and olives are because they will probably be tight on the pipe (the olives) and hacksawing through them will not only take a long time, but may damage the pipe (pinhole it possibly) and it will be awkward sawing near the wall/skirting board.

 

[seco services]

some tank connectors don't take bungs very well and won't seal.

you can use the same nut and olive providing its not damaged or been overt tightened

 

[oliverwilliams]

ah so it is true ... so what can i do to overcome this problem? will ptfe tape help seal it/make it larger and fit better? any tips?

yes that's what i feared - i suppose if the olive does look badly damaged i'll need one of those olive tools do remove it? they any good, through your own experience?

 

[spacethegas]

may sound silly but you can push a potato on to the open vent & stick a carrot in the cold feed. better still just shut the cold feed gate valve.

olives can be partially sawed through (carefully) & then split by twisting a screwdriver in the cut.

 

[oliverwilliams]

there isn't a gate valve on the primary cold feed to the heating circuit, and it's dangerous if there was! but thanks about the carrot and potato tip!!!

the olive tip is useful to know too.

i did remember hearing something about ptfe tape rolled thickly around a bung/plug would help make a good seal in the cold feed? also someone mentioned something about serrated edge tank connectors being hard to block? is this true, i've never seen a serrated edge connector though myself?

 

[spacethegas]

there isn't a gate valve on the primary cold feed to the heating circuit, and it's dangerous if there was!

no its not. standard procedure on all good open installations.

dont get ahead of yourself. the chances are that you will have no problem.

 

[Agile]

Some wine plastic corks are good too!

Tony

 

[Agile]

before you change it are you sure that the TRV head has not just been wrongly adjusted inside?

There is a mechanism for setting the calibration point.

You could also blow a hairdryer at it and see if that moves the plunger.

Tony

 

[oliverwilliams]

Agile - hi. the TRV head has been fine for years - what exactly do you mean about a mechanism for a calibration point? Do you mean when the head is firmly/correctly screwed on to the valve body?


the plunger/pin in the valve is not stuck though, it is fine, just when the head is on, the rad doesn't heat up, so i am assuming, pretty certain, the head has worn/the gas bellows have expanded and not contracted (is faulty)

 

[spacethegas]

what sort of trv ?

 

[oliverwilliams]

it's a normal type, a drayton.

why?!

 

[spacethegas]

if your saying its a trv4

Untitled

• spacethegas
• 7 Oct 2008
• 1

just buy a new one & swap the head.