TRVs not responding to room temperature

[Little Clanger]

I've fitted Pegler Bulldog TRVs to all my radiators, but they don't seem to be responding to room temperatures.

 

On '0' they shut off the flow OK, but on any other setting they come on regardless of room temperature. For example, with the radiator turned off, I left a thermometer (on a Horstmann room thermostat sender), adjacent to the TRV. I left the thermometer to settle, which it did at 15^o. According to the Pegler information, the TRV should have opened at this air temperature when set at '2' (15^o - 17^o), however, it opened as soon as I got to the frost setting, '*', which is supposed to be 7^o.

 

The thermostatic heads are seated down properly and the locking ring is tight. I've tried changing the heads, but same result.

 

Any ideas, or have I misunderstood how they are supposed to function?

[Marvin]

It suggests the head may not screwed down to the body correctly. You have to rotate the head into the groves of the body before screwing the collar. (the groves stop the head rotating before the collar is screwed up

 

It may be that the head has not warmed up yet. The head has an expansion vessel in it which pushes down on the top of the pin which closes the valve. the expansion vessel takes time to respond.

 

The rad valve may be colder than 15C and need to warm up.

 

The product is faulty.

 

Many other reasons that clever people will come up with.

 

Good luck

 

M

 

[John Carroll]

Ensure the actuator is turned fully anticlockwise (fully open) before attaching it to the valve.

[-rick-]

Is the plunger on top of the valve body free to move? Sometimes they stick and need manual manipulation to free up? If the valve body is new I doubt this is a problem. But not sure if you've just changed the TRV or the TRV + valve.

[Little Clanger]

  On 12/01/2025 at 12:04, Marvin said:

It suggests the head may not screwed down to the body correctly. You have to rotate the head into the groves of the body before screwing the collar. (the groves stop the head rotating before the collar is screwed up.

 

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Thanks for your suggestions.

Think the head is on OK. On these, there is a female hex on the head that fits on a male hex on the body.

 

  On 12/01/2025 at 12:04, Marvin said:

 

It may be that the head has not warmed up yet. The head has an expansion vessel in it which pushes down on the top of the pin which closes the valve. the expansion vessel takes time to respond.

 

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The expansion vessel appears to work - I took the head off and ran a hair dryer over it and the pin in the head definitely moved.

 

Thanks again 

[Little Clanger]

  On 12/01/2025 at 13:24, John Carroll said:

Ensure the actuator is turned fully anticlockwise (fully open) before attaching it to the valve.

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Thanks.

 

Yes, discovered that!

[Little Clanger]

  On 12/01/2025 at 14:00, -rick- said:

Is the plunger on top of the valve body free to move? Sometimes they stick and need manual manipulation to free up? If the valve body is new I doubt this is a problem. But not sure if you've just changed the TRV or the TRV + valve.

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Thanks.

They are new TRVs and valves.

The pin in the valve does push in when you put finger pressure on it. And anyway, it shuts down OK, when set to '0'.

 

The pin in the head moves when heat is applied (when removed), so it's expanding OK. The total movement of the pin is only about 10mm from shut to fully open, so presumably only about 2mm of movement for each progressive setting. It's as if the pin needs to be fractionally longer, or the head screwed down tighter to shorten the distance. I've only done the collar up finger tight for fear of damaging it. Perhaps grips would pull it in a little more.

 

Anyway, thanks again 

 

[John Carroll]

  On 12/01/2025 at 14:34, Little Clanger said:

Thanks.

They are new TRVs and valves.

The pin in the valve does push in when you put finger pressure on it. I've only done the collar up finger tight for fear of damaging it. Perhaps grips would pull it in a little more.

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NO way should finger pressure push the pin in except you're Superman with a steel finger, I use the handle of a reversed hammer to push the pin in, it should then spring back out ~ 3/5mm. Any failures I've had is that the spring fails, so they won't open once the temperature drops, I've never had a actuator failure apart from some ancient ones where the plastic has become brittle and they have fallen off.

I've just noticed a pin (valve) failure on one of my EPH TRVs, a bit disappointed as these normally last ~ 8 years, this one is only 4/5 years old.

 

I often see reference (like above) to the pin sticking say after a summer of no use but I've never experienced this, most of my TRV (8) settings are never touched throughout their lifetimes.

[Little Clanger]

Again, thanks, John

 

  On 13/01/2025 at 06:38, John Carroll said:

NO way should finger pressure push the pin in except you're Superman with a steel finger, I use the handle of a reversed hammer to push the pin in, it should then spring back out ~ 3/5mm.

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Well I can definitely push the pin in the body in with finger pressure, although with difficulty, and the pin springs out again OK. The fact that it shuts down on '0' setting but then opens on even the frost setting suggests the valve is opening and shutting properly.

 

I've just had a closer look, with a torch shining though the vents in the head. With the adjacent air temperature 15^o, when the TRV is set on '2' (15^o - 17^o), the expanding capsule is still loose in the head - there is a small gap between the top of it and the fixed bridge that it bears on, and you can wobble it with a knife. I would have thought that, considering the open/shut temperature range for this setting, it would at least be bearing on the valve pin and possibly starting to push it in to shut off the flow.

 

This sort of confirms for me that the head isn't seating down properly and so increasing the distance between the valve and actuator pins. I tried tightening the collar with grips, but it didn't make any difference. The weird thing is all the TRVs are behaving like this!

[-rick-]

  On 13/01/2025 at 06:38, John Carroll said:

NO way should finger pressure push the pin in except you're Superman with a steel finger, I use the handle of a reversed hammer to push the pin in, it should then spring back out ~ 3/5mm.

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Interesting. All of my valves I can press down manually (no tools). It's stiff sure but definitely movable by hand.

[John Carroll]

  On 13/01/2025 at 11:21, -rick- said:

 

Interesting. All of my valves I can press down manually (no tools). It's stiff sure but definitely movable by hand.

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If I use my thumb with something covering it,  then, yes, can push it, but not easily, maybe thats why my pins never stick in the one position!.

At index 2 my actuator will certainly be pushing the pin in a fair bit and will be fully shut off at a room temp of 18/20C, all these (proportional) actuators work the same, at a fairly low setting like index 2, the valve will only be a mm or so from fully shut so a relatively small temperature rise will throttle it still further and even close it, I would think that the actuator should just about be touching the pin even on setting 5 with the valve just fully open

I will be purchasing/replacing one in the next few days so will take a few readings before installing it.

[John Carroll]

Got the new EPH TRV, its indexed 0 to 5.

At a OAT of 7C and leaving the TRV outside for a hour or so, I only have to decrease the setting to 4.0 when the actuator then contacts the push pin. Inside, after allowing it to heat soak for another hour or so, the push pin starts to move immediately on turning the actuator from index 5 (max). At setting 2.5 (which gives me ~ 18C),  the valve is only ~ 1.5MM off its (closed) seat at a temperature of 15C or so.

Edited January 21 by John Carroll