TRVs (Honeywell) have VERY limited (if any) adjustment range

[tommcdonna]

I've recently moved into a new house fitted with Honeywell TRVs on all the rads.

The valves obviously have some effect, as I can turn the rads on and off with them, but there doesn't seem to be any adjustability, they're either full on, or totally off.

I would normally expect (as in other properties I've been in) that setting them at about "2" or "3" would be comfortable. But if I leave them at that setting, it's unbearable.

If I set the valves about half way between "*" and "0" if I leave the heating on too long all rooms become unbearably hot so evidently with the valves set (theoretically) so low, they're not working properly.

Is this because they have become "sticky" and I may be able to fix it by removing the tops and "exercising" the pins?

Or can they be adjusted somehow so the usable range is "0" to "6" rather than "0" to "*"?

 

[D_Hailsham]

Could be the pins, so worth checking them.

How old are the TRVs? The sensor in the removable top does not last for ever, so it may be a case of replacing the top.

Edited - just saw that you have Honeywell valves!!

The system could need balancing. Depending on which Honeywell valves you have, balancing may be done by turning the numbered ring which is exposed when you remove the valve top. Others are balanced in the usual way by closing down the lockshield valve.

 

[JohnD]

if you can turn the rads off by screwing down the tops, and they come on if you wind the knob up, it won't be stuck pins.

I have some oldish Honeywell TRVs and mostly the thermostat part has failed and they are mostly fully open.

They aren't popular enough to have replacement heads readily available at reasonable price so I'm changing them to TRV4s. As I'm doing all of them I'm draining down on a warm day (incorporating this in my system cleaning schedule)

I sent a pic of my old ones to Honeywell to see what heads were available, you may be luckier than me if yours are a recent/popular style. There is a "contact us" link on the Honeywell Controls web page.
try https://www.honeywell.com/sites/portal?smap=honeywell_uk&page=contact-us&theme=T9&c=n

 

[tommcdonna]

Response to D_Hailsham:

I'll give fiddling with the pin on one of the rads a go, see what, if anything happens. The tops look pretty old to me so maybe it could be that. Are they expensive to get?

They look like these, though I'll have a better look later, would there be a model number on the valve anywhere?

http://www.plumbworld.co.uk/honeywell-vt117e-0000-12664

It's a rented property so I don't mind paying a small amount to fiddle, but I'm not keen on any significant expense.

By "balancing" do you mean just turning the lockshield down a bit on all the rads? When the house is cold, all the rads seem to heat up at the same rate, none lag massively or get piping hot before the others.

 

[tommcdonna]

I have some oldish Honeywell TRVs and mostly the thermostat part has failed and they are mostly fully open.

Sounds like that's the most likely scenario, phone call to landlord I think...

 

[D_Hailsham]

would there be a model number on the valve anywhere?

I have never found one on my Honeywell valves, but if it looks like the VT117 in the pic it is the VT117. This model has the balancing device built in to the valve.

By "balancing" do you mean just turning the lockshield down a bit on all the rads? When the house is cold, all the rads seem to heat up at the same rate, none lag massively or get piping hot before the others.

Basically, yes. The aim of balancing is to ensure that the temperature drop from input to output is the same for all rads. This ensures that the earlier rads do not grab all the heat, leaving none for the later ones.

As your rads appear to be getting equally hot, they are probably balanced reasonably OK. Which leaves faulty TRV heads as the possible solution. It might be worth buying a new Honeywell TRV (the VT200 and VT117 heads are interchangeable) and trying out a new head on the existing body.

 

[tommcdonna]

I have never found one on my Honeywell valves, but if it looks like the VT117 in the pic it is the VT117. This model has the balancing device built in to the valve.

I had a closer look at the valve, it's one I recognise as having seen all over the place before. It's the same valve as used in my last house, the CH there was all replaced around 15 years ago so they could be pretty old.

The heads screw on with a metal collar, which surrounds a black plastic mount. The head itself is cream coloured, with black numbers and a black button which gives a click as you turn it past "3". Also a black "lid". The valve has numbers embossed around this pin so I'm guessing it's a model with built in balancing.

Basically, yes. The aim of balancing is to ensure that the temperature drop from input to output is the same for all rads. This ensures that the earlier rads do not grab all the heat, leaving none for the later ones.

As your rads appear to be getting equally hot, they are probably balanced reasonably OK. Which leaves faulty TRV heads as the possible solution. It might be worth buying a new Honeywell TRV (the VT200 and VT117 heads are interchangeable) and trying out a new head on the existing body.

I removed the heads and checked the motion of the valve pins, all 4 open and close smoothly as they should. Having examined the heads more closely I can see how the valves work, with a brass capsule pushing a pin out as they heat up. The pin on all the capsules is retracted.

Holding the head over a heat source for a few mins (a light bulb), there was no movement. Immersing the capsule in boiling water, the pin moves right out, far enough that it would switch the rad off if it were fitted. It shouldn't need that much heat to move though, so I think the diagnosis of the heads (more specifically the capsules inside) being shot is correct.

I'll take one of the heads into my local plumbing supplies place and see if I can get a replacement that will fit to give it a go.