Faulty TRVs?

[kamoshika]

All the radiators in our house (except one, which I understand should be the one in the same room as the thermostat, but isn't) are fitted with Myson 2 way TRVs. On some of them the TRV seems to be faulty as the radiator stays off even when the room is very cold, and the heating system is on.

I've read the wiki article (//www.diynot.com/wiki/plumbing:thermostatic_radiator_valves_-_trvs) and I don't think the problem is with the valve sticking - as soon as I remove the head the radiator heats up. So far I've just removed the heads from all the radiators where we've had this problem and that's fine, but it does mean we've got no control over how high we have the radiator in each room.
Is my only option to buy replacement heads or is there another solution? Do I need to replace the heads with TRV ones, or is there a "standard" radiator control that will screw onto the the TRV valve?

If I do get new heads, are they a standard fitting? (ie will I need to buy Myson ones) We've had problems with 4 of 7 so far so I'm not that impressed with them. The house was new build 5 years ago and speaking to neighbours others have had problems too. Are the Myson TRVs just not very good, or have we just got a faulty batch?

Thanks for any help anyone can offer.

 

[kamoshika]

Bump...... anyone got any advice?

 

[Meme21]

Bump again - I have similar problem only two of mine won't switch off or turn down

 

[D_Hailsham]

Firstly, remove the head from the TRV in the room which has the wall thermostat. Then check what happens in the other rooms.

... as soon as I remove the head the radiator heats up.

Then, as you say, the valve is not sticking. What happens if you set the valve to a higher number; or does the rad not heat up even when the valve is on max?

The problem could be due to poor system balance. See How to balance a CH System

Is my only option to buy replacement heads or is there another solution? Do I need to replace the heads with TRV ones, or is there a "standard" radiator control that will screw onto the the TRV valve?

No such thing as a "standard" control to replace a TRV head. Wheel head valves work in a different way - they are a bit like basin taps with a screw action. TRVs use a plunger.

You would have to buy Myson heads.

 

[kamoshika]

Firstly, remove the head from the TRV in the room which has the wall thermostat. Then check what happens in the other rooms.

The wall thermostat is in the living room, which has 2 radiators. Both of those have had this problem and I've taken the heads off, so they're on full. Once the room gets to the temp set on the wall thermostat the heating turns off. Until then the other radiators are on (if they've got a working head, or I've removed the head) or off (if they've got a faulty head)

What happens if you set the valve to a higher number; or does the rad not heat up even when the valve is on max?

Doesn't heat up, even when set on max.

The problem could be due to poor system balance. See How to balance a CH System

Thanks - will have a look at that.

No such thing as a "standard" control to replace a TRV head. Wheel head valves work in a different way - they are a bit like basin taps with a screw action. TRVs use a plunger. You would have to buy Myson heads.

I thought that was probably the case. Are the Myson heads usually thought to be OK?

Thanks for the help. I'll have a look at the system balance page and see if that helps. If not I guess I'll need to buy some new heads.

 

[TonyW2]

I have had similar fault with 5-6 old year new build house Myson TRVs and Myson were very good in supplying free replacements by post. there did seem to be a known problem, and I think the internal design has been changed a little.

 

[kamoshika]

Thanks Tony - that's very useful to know. Our house is just coming up 5 years old, so they're a similar age. I'll try getting in touch with Myson and see if they willing to replace them.

 

[D_Hailsham]

What happens if you set the valve to a higher number; or does the rad not heat up even when the valve is on max?

Doesn't heat up, even when set on max.

Not quite clear, but do you have some TRVs which work and some which do not? If so, what happens if you swap a good head for a bad one? This will help you identify if it is a head problem or not.

No such thing as a "standard" control to replace a TRV head. Wheel head valves work in a different way - they are a bit like basin taps with a screw action. TRVs use a plunger. You would have to buy Myson heads.

I thought that was probably the case. Are the Myson heads usually thought to be OK?[/quote]
They don't have a bad reputation. In any case the current heads will be "better" than the ones you have.

Myson TRV Leaflet

 

[machine19]

Hello

These valves are a pain in the you know what. They have a design fault in the head. That is, there is a badly designed plastic component which fails prematurely (I have dismantled one to see what the problem is). I have had at least 5 fail in the same manner on different radiators over 3 to 4 years.
That is the mechanism fails and completely shuts off the valve, and this can happen overnight. Failure in this way can be ascertained if you remove the head (a loud click is heard as the pin jumps out) and look at the actuator pin (in black plastic) that bears on the valve plunger this will be fully extended and will not move what ever you do with the heat setting. Hence cutting off the flow. In my opinion they are an overpriced valve. I have used cheap own brand valves from Wickes/B and Q which work more reliably than these Myson valves which incidentally were reccomended by my local plumbers merchant as " A better quality valve".

As an aside believe that a major factor in keeping any TRV valve bodies working well is lubrication of the plunger with an 'o' ring compatible oil and the use of a good inhibitor in the heating system to prevent corrosion.

All in all it has cost me more in new valves than the savings on heating bills since the system was put in!! Draw your own conclusions about myson valves!!

Alan

 

[NigelAB]

Had exactly similar problem in similar age house. Had 4 of 8 heads fail. Tried Myson for freebies no luck. Offered heads for about £15 each, but no-one seemed to recommend. A wickes TRV was highly recommended on here, about £7 each complete. Went to wickes, only stocked online. Went to B & Q, bought 4 at £7.18 each. Thought I had to drain and replace complete, but decided to try B & Q head on Myson valve. Seems to fit and work perfectly!! So half the cost, no mess, 15 minute job and I still have spare valve bodys if I need. Stroke of luck. It is the PlumbSure TRV from B & Q

 

[Charnwood]

Most TRV heads fit most TRV valves - but not all.

 

[Agile]

I always thought that they mostly did not!

But Danfoss new radio valves will fit most makes they say!

Tony

 

[Agile]

Contrary to what is said above I have found the Wickes valves as very likely to stick.

Tony

 

[Charnwood]

I always thought that they mostly did not!

But Danfoss new radio valves will fit most makes they say!

Tony

Danfoss has always been a b'stard size

Interchangeables:
Pegler; Belmont and Terrier
Honeywell
Yorkshire Mistral
Altecnic
Myson
Drayton, I'm fairly sure
Boss
Dumbcentre's own brand
Most of the sheds own brands

I am going back a few years to my time as a counterboy. Some might have changed.

 

[Agile]

I find it very annoying that the Drayton TRV is a different size head to the ( much better ) TRV 4

The Danfoss radio valves come with an adapter which is sometimes needed for other makes.

Tony