Advice on replacement of old TRV Heads

[martinfd]

Hi guys,

I'm trying to improve the old central heating system in my house as much as possible, this week I'm looking at the TRVs. I've got 7 rads with old Danfoss TRVs (see pictures below). A few of them don't seem to be working very well, so I was thinking about replacing the heads. I've removed the heads and it looks like the pins in the valves are moving freely, so am I right to say that replacement heads should be enough? Obviously if I can avoid replacing the whole valve, that would be good.

I wasn't entirely sure what type of TRV head I needed, but I found this page which suggests they're 17mm RA:
http://www.heatingcontrolsonline.co.uk/danfoss_table.php

That site has two suggested products, RAS-C2 which looks like the direct replacement for what I have, and the RA2910 sensor. Can anyone explain what the difference is between these two heads? I know some TRVs have remote sensors, is the RA2910 for connecting to a remote sensor? As it happens I've got two TRVs that are covered by curtains, so a remote sensor might be a good idea for them?

http://www.heatingcontrolsonline.co.uk/danfoss-randall-ra2910-sensor-p-375.html
http://www.heatingcontrolsonline.co.uk/danfoss-randall-rasc2-replacement-heads-p-324.html

I've also noticed that one of the glands has a small amount of water coming out around the pin. I found a Danfoss part guide that the replacement gland part is 013G0290, but those seem to be hard to find - I found an eBay listing for it from Germany but that's about it! Any advice on that?

Finally... if I ever have to replace a whole valve, any advice on the size of fitting I get? I'm assuming these aren't 15mm due to their age, do TRV valve sets generally come with the necessary adaptors to fit? (if you can't tell, this is me getting a bit out of my depth so I don't know if I'm asking the question correctly).

Thanks for you help!

 

[Aquaheat]

A few of them don't seem to be working very well, so I was thinking about replacing the heads.

What do you mean by not working well and what are you hoping to achieve would be a good start.

Jon

 

[martinfd]

Sorry,

A few of them don't seem to be working very well, so I was thinking about replacing the heads.

What do you mean by not working well and what are you hoping to achieve would be a good start.

Jon

Sorry, at least a few of them don't seem to be responding appropriately to changes in temperature in the room. For example, we have a wood burning stove in the living room, which can make the room very warm. However, one of the radiators was still on when the TRV was set to 3. The pin on the valve seems to be moving fine, so I assumed it was a problem with the TRV head. I don't know for certain if they're all behaving the same way, but I figured if I was going to do one I'd just update them all, and that would give me a bit more confidence about setting them and trusting them to work correctly.

 

[Aquaheat]

OK well if you were heading down that route and for the slightly smaller outlay in cost I would consider replacing the entire valve as you then have a guaranteed fully functional unit for many years to come.

I would look at the Drayton TRV 4s they are a quality bidirectional valve with a pretty accurate (about 1/4 degree) liquid sensor.

The units are fully serviceable so spares can be found and repaired rather than replaced and are available in the sizes that you need.

Oh and I'm independent and don't work for them but you'll find a lot of guys have them on here as do I.

If you wanted smarter technology you could look at Evo home or heat genius to replace heads and have online control and independent control of rooms but that comes at a hefty price.

Jon

 

[martinfd]

OK well if you were heading down that route and for the slightly smaller outlay in cost I would consider replacing the entire valve as you then have a guaranteed fully functional unit for many years to come.

I would look at the Drayton TRV 4s they are a quality bidirectional valve with a pretty accurate (about 1/4 degree) liquid sensor.

The units are fully serviceable so spares can be found and repaired rather than replaced and are available in the sizes that you need.

Oh and I'm independent and don't work for them but you'll find a lot of guys have them on here as do I.

If you wanted smarter technology you could look at Evo home or heat genius to replace heads and have online control and independent control of rooms but that comes at a hefty price.

Jon

Thanks Jon. I've seen the TRV4 recommended quite a few times, and I take your point, if I'm going to do this properly, I might as well replace the whole valve for a little more money. I'm just a little nervous about figuring out the right fitting sizes - I've done simple work on rads before, but only on modern systems where everything was using standard 15mm fittings.

I've looked into evohome - by my sums the payback period is too long for the initial outlay (14 rads in the house), but I'm considering something like a Nest (which I was hoping would work better if I had reliable TRVs!)

 

[Aquaheat]

Well they are standard half inch into the rads the only bit that changes is the copper from the floor to the valve. It's hard to say for 100% from your picture but it looks like 10 mm. The valves come with insets that reduce it down from 15mm to either 12/10 or 8mm. Just measure across the outside diameter of your pipe and you will know for sure.

Agree about the payback on the Evo home amongst others. Nest would be an option but it wouldn't work best in a room with a log burner as this would throw it out with its learning function. Hallway would be best. The TRVs will help but the main benefit from them is to be able to heat up the home or cool it down for periods where you are in or not and what kind of temperatures you normally use. This learning feature is pretty good. It also compensates for the weather outside. It's not true weather comp but Internet based for your area so could be a couple of degrees out.

Depending on what boiler you have at the minute it may or may not matter that it doesn't have true open therm at the minute but they are promising it with a software update but no dates sey as yet. 3rd gen has hot water control too but again depends on your boiler. If you have a combination boiler then this is not used.

I do kind of like the nests there will be one going in my house soon but it would be dependant then on what kind of functionality you want.

Jon

 

[martinfd]

Well they are standard half inch into the rads the only bit that changes is the copper from the floor to the valve. It's hard to say for 100% from your picture but it looks like 10 mm. The valves come with insets that reduce it down from 15mm to either 12/10 or 8mm. Just measure across the outside diameter of your pipe and you will know for sure.

Right ok, so, if I buy the TRV4 valve set, I should be covered. Thanks.

 

[Aquaheat]

Should be Martin. Like I said just measure the OD of the pipe and you will know for definite but my money is on 10mm.

If you order 10mm valves they will come with inserts but you will probably get away with using the existing nuts and olives and just switching the valve bodies over. A little smear of boss white or jet blue on each of the joints on the valve side of the olive and you should be able to switch each one over in 10 minutes tops.

If you drain the system be sure to top up with a good quality inhibitor.

Jon