danfoss radiators won`t stay off

[inmcdonalds]

Hi

Just moved into a new house a month ago. Oil fired central heating for a 5 bed bungalow. Got a bit of a shock when I realised we went through 800 litres of oil in last 6 weeks

Anyway I`m now trying to implement a more rigorous energy management system, shutting off rooms radiators at different times of day to correspond to when they are used most etc etc.

The radiator thermostats are quite old Danfoss ones (i`ll try to post a picture). They are numbered 1-5 with no `*` for defrost setting and no `0`. You can turn it all the way round as far as it goes to below `1` which I was thinking equates to `0` and means the radiator is off.

However, those radiators turned all the way to the lowest setting are actually still coming on full blast every now and again.

My question is, does this mean that the lowest setting is like some kind of anti-freeze setting and it will come on sporadically? (if this is the case I will invest in ones that truly switch the radiator off)

Or are the radiator valves just jiggered? (in which case I guess I`ll need to replace them anyway!)

I really would like to be able to switch off certain radiators and know they will stay off and not therefore use up my oil!

Untitled

• inmcdonalds
• 25 Mar 2013
• 1

Untitled

• inmcdonalds
• 25 Mar 2013
• 1

 

[Slugbabydotcom]

Looking at the data for the new version of RA/VL head they do have a min temp of 5degC so it would suggest these are the same.
There is no 'on just a bit' setting! The rad comes on until the set temp is reached at the sensor.
These valves are notorious for sticking in the off position so it's maybe not a bad idea to replace them anyway

 

[inmcdonalds]

So I guess that means you can never turn the radiator completely off by means of the radiator thermostat if the min temp is 5 degrees. Although I'm sure the rooms in question aren't getting that cold...

 

[Slugbabydotcom]

Put a thermometer next to your TRV but slightly away from the rad. It may be in a draught or it could be a faulty actuator head.
From the time I spent playing about with an infrared thermometer I can tell you that there is often a few degrees between floor and head height temp due to stratification of air.

 

[inmcdonalds]

If the stat is too sensitive, is it just a question of replacing the plastic thermostatic head? The pin or valve that is underneath it seems to move in and out okay. I`m guessing just removing the plastic bit would be easier/cheaper than replacing the whole metal valve mechanism which would entail draining down the system.

And if I can just try replacing the plastic bit, how do I know if it will fit on to the metal part ie is there a standard fitting or do I need to match the existing sizes?

(probably should learn the names for all these things!!)

 

[Slugbabydotcom]

Looks like a RA/VL head to me I remember buying some heads a few years back that looked exactly like yours. I believe THIS is the latest version.
Shop around and you might find them cheaper.

 

[inmcdonalds]

That looks like it might be the right one to me. The video below which shows the old style is a dead ringer for the one I`ve got.

I`ve spoken to a plumber who is coming round for a chat. I think he is keen to replace both the stat and the valve ie he will have to drain the system, which i know will be pricey as there are 20 to do. His argument is that the valve is probably faulty although I`m not convinced and I think will try a DIY job on one of the radiators to replace the head only and see if that helps.

 

[Slugbabydotcom]

That sounds like a good plan to me. If the rads go on and off then it seems unlikely that there is a problem with the brass part of the valve and it is just an issue with the head.
The reason I have experience of these is that every September I would get a call from a local dentist surgery and have to go around most of the valves freeing them off as they had stuck in the off position. These were earlier valves than yours. I found that I could pull the pin out, apply some silicone grease and put it back in the opposite way and while I was there tap the valve to free it. I would know the valve was open when it got hot. Never once did I have to drain the system off.
I did advise that turning the valves to 5 at the end of the heating season would stop them sticking but every year I still got the job. From their point of view it made economic sense just to get me back every year than replace the valves.
Over a period of about 9 years I replaced about 6 of about 15 valve heads