Honeywell TRVs

I've been struggling trying to balance my radiators. I noticed in SEVERAL unimportant rooms (utilty, toilet, etc) that the rads get very hot even with the LSV down to 0.5 turn open AND the TRV set to snowflake.
Seems like bad TRVs, so I bought one new one as a trial and confirmed this (now fixed in that room).
A bit of Googling revealed someone stating TRVs have a limited life, eg 5-7 years. These might be 15 years ! So that appears to be true.
If I'm going to swap ~10 of these, then it's not cheap, as I just paid 15 for one LT117E Also they don't sell the head only. Out of interest, what is the fail mechanism ? I guess no chance of fixing ?
Thanks in advance.
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Mine are Myson. Currently 15 years service. Two have given trouble due to lime scale jamming the valve plunger. Judicious scraping (bit of brass plate) and jiggling with round nose pliers has got them working again.
Mine always fail closed.
I have considered asking in here if there is a suitable lubricant but you can if you like:-)
regards
--
Tim Lamb

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Pins usually get stuck closed not open: tapping the pin with a small hammer or anything similar usually pops them up again.
But it sounds like you need to do some balancing. Most of the on/off action of the lock shield valve is in the first half turn, so you are probably being over generous with your half turn, and a nudge of an eighth of a turn can make the difference between hot and cold. I would start by shutting the lock shields of the rads that get too hot right down, and then cracking them open an eighth of a turn at a time until you get the temp you want. I find I have to make small adjustments most years, and don't put the lockshield screws back in, to make it easier to just tweak any a bit when you notice them starting to run cool.
You can also experiment with the pump speeds. Set the pump to the lowest speed that will keep the rads warm, and it will last longer and run more quietly. If the rads won't balance at the slowest speed, move up a notch and try again.
S
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<snip>

The pin inside the valve in the rad coupling seems fine. I can push it in ~ 1/10" and it springs right back. It really looks like TRV heads shot. A new TRV head fixed the utility room.

I agree most of the "action" on the LSVs is near fully closed.
I would start by shutting the

This is a big, old house with an extension. The pump is, and always has been (even before we moved here) at max. Even so, the the last rad struggles to get hot enough with both LSV and TRV fully open. Hence I want to cool down some of the less important rads - toilet and utility room.

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Mystery solved.
The thermostat heads "fail" because the spring becomes weak. This means the pin in the coupling valve can push it back as it has a very strong spring.
It's a damned shame to have to pay ~ 13 for a complete VT117e when all that's wrong is the spring.
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I may be a bit daft - but I use stethoscope to establish the point where the valves stop the flow. Handy when setting a thermostatic valve. When the room is comfortable - turn the temp control slowly down until you hear the flow start to choke. Lock the valve to stop SWMBO fiddling.
Also handy with lockshields.
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An eighth of a turn is not an uncommon setting for a LSV on a titchy rad in a small room.
--
fred
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