TRV's - Universal??

[Nozzle]

Hi everyone,

Are TRV's universal? By that I mean, do the thermostatic elements that is screwed down onto the valve itself have a common, defined thread (ISO or BS or something) and does the element expand the same amount per degree?

The reason I ask is, some of my TRV thermostatic elements are looking old, quite sizeable, and not so easy to adjust as a result. In an ideal world, I could just buy some new caps, screw off the old ones and replace with brand spanking new ones without having to worry about compatibility.

Nozzle

 

[Newboy]

Sadly not.

The mechanism attaching the heads to the body tend to be unique to each manufacturer - if you've got a branded valve then it's usually possible to get a new part.

The actual thermostatic element is usually within the valve body - not in the head itself, so if that's the bit that's failed/sticking then it's time for a new TRV

 

[Nozzle]

Ah crud Well, thanks for the reply then. It looks like I have my work cut out if I'm serious about updating them.

Nozzle

 

[Dan Robinson]

There are 2 common sizes, and various other minority offerings.

M28 and M30 are the thread size of the common two.

Try posting a pic.

 

[D_Hailsham]

The actual thermostatic element is usually within the valve body - not in the head itself

You have that completely ar*e about face!

 

[Newboy]

I do indeed - and have no idea how the h*ll I wrote most of the drivel I've apparently posted on this thread!

OP - please ignore my replies and I'll learn to sign out!

 

[Nozzle]

As suggested by Dan_R - A picture:

Untitled

• Nozzle
• 15 Dec 2014
• 1

It's Honeywell, and has no part number stamped, silk-screened or moulded into it. The house is 1970s, I don't know if the central heating is original stuff.

Nozzle

 

[Dan Robinson]

It's a VT117 with m30 thread.

Compatible with loads including the VT200.

 

[Nozzle]

Wow, thanks for the very accurate info! Now I just need to find a supplier of TRV heads only. Is it even possible to buy the heads only??

Nozzle

 

[D_Hailsham]

The VT117 replacement head is part no T100-353

You can also fit the VT200 head, part no T200-263.

The VT200 looks similar to the Drayton TRV4 (there was even a patent infringement case about this).

The main difference is that the VT117 head has a wax filled sensor but the VT200's sensor is liquid filled, which means it responds faster to temperature changes.

 

[Boilerman2]

A Drayton TRV4 head will fit the Honeywell valve body

 

[muggles]

Wow, thanks for the very accurate info! Now I just need to find a supplier of TRV heads only. Is it even possible to buy the heads only??

Nozzle

It is, but it's often almost as much as a complete valve. The Honeywell VT200 is now known as the Honeywell Valencia Classic, and the order code for the head only is now T4021GB for white/chrome (all chrome, all brushed chrome and black/chrome are also available).

 

[Marmorkirken]

Hi there. This TRV keeps popping off anytime someone brushes up against it, presumably because the plastic ridge is worn out. Would you say this is a Herz “classic thermostatic sensor”? And if so would you recommend replacing it with the same or is this a design issue that would be best swapped out for something else?

Herz Valves UK Ltd. - Classic Thermostatic Sensor

herzvalves.com

 

[Deleted member 267285]

Looks similar and may work. The retaining ring doesn’t appear to be attached, which will be why it’s coming off.