**SOLVED** Danfoss TRVs with 'incorrect' flow setting

[magicmanalex]

Hi Folks,

We moved into a house 18 months ago. It was built in 2007 and has a 2007 Potterton Powermax HE boiler. Eleven radiators in the house, various sizes.

Against our better judgement, we took my mother's advice and turned off the radiators in two unused bedrooms, to prevent heating up unused rooms. After reading advice on forums, I'll never turn one completely off again (except for removal). Lesson learnt.

We put them back on recently. The main bedroom is working fine, the smaller (office) bedroom with a tiny rad will not get warm at all. 10mm plastic pipe on all radiators.

The other rads in the house get very hot, top and bottom . The whole house (except the office) is lovely and warm.

On the office rad, I have:

• Removed TRV plastic 'head' section and gently pushed the pin up and down (many times). Tapped the side of the body with a hammer. Put a bit of WD40 on the pin.
  
  
• Open and closed lock shield valve a good number of times.
  
  
• Ruled out airlock by turning both valves off. Dissipated water via bleed nipple then removed bleed nipple. Connected a braided filling hose to bleed nipple hole (and up and out of the window) and one-at-a-time opened both lock shield and TRV valves.
  
  
• Turned off all other TRVs in the house to 'force' more flow into office RAD.
  
  No change. Both plastic pipes still remain cold (although the one with the TRV did get the TINIEST bit lukewarm at one point). Near unnoticeable though.

I'm thinking potential pipe blockage or faulty TRV. Water coming out of the bleed nipple is very clean and clear (probably because we're filling up our boiler on an almost-daily basis - different issue).

Or I'm not sure if the 'sludgy' sediment sinks to the bottom of the rad so that just very clean, clear water comes out of the top.

I have yet to flush the rad or do the 'bucket' test. Draining all the rads will be a swine because I don't have a drain valve on any of the downstairs radiators, so I'll have to remove one and find something to connect a hosepipe to one of the two radiator valves.

Anyway, I have this morning found the TRV's grey collar which has both an up arrow and a down arrow which must be lined up with the little mark on the body to suit flow direction.

I've checked all of our rads, about half of these are set 'incorrectly'. (i.e. on the pipe that gets hot first, the arrow is pointing downwards). I've had a look Danfoss's PDF file for the RAS-C2 and it says it should be set to 'up-arrow' for flow and 'down-arrow' for return. The rads do get lovely and warm though. I couldn't ask for better performance (except for the office one!)

I want to set them all to the 'correct' orientation before continuing but the girlfriend has (quite justifiably) said - if all of the other radiators work fine and it's been this way for this many years, why change it?

I'm a great believer in 'if it ain't broke don't fix it' but could correcting the setting on about half of the radiators introduce any problems or should I leave well alone? The setting obviously exists for a reason....

 

[dilalio]

I'd say they're sludged up.
If it's a tiny rad, take it off and flush it through with a hose pipe. Bang it with a rubber mallet while doing so. Worst case, buy a new one - small ones are cheap as chips. You could also connect a bit of hep across the trv and Lockshield while the rads off and see if you can flush out any debris in the valve(s).

 

[magicmanalex]

Lovely. Thanks for the quick reply Dilalio.

I removed the rad and flushed it out with a garden hose. Water was perfectly clean. The TINIEST bit of black water as I removed the radiator from the wall, but certainly nothing that would clog it up. I've fitted decorator caps to the lock shield valve and TRV just to be on the safe side.

Now I believe it's time for the bucket test. The central heating is still on. Do I now switch off the central heating, wait for a while and then open one of the two valves into a bucket to check for flow for 30 seconds? (And assuming that there is flow, close it off and then repeat with the other valve?

Or does the central heating need to on to do this, so water is actually being pumped?

(Just being cautious!)

 

[dilalio]

You can leave it on, just be cautious with hot water! Open the Lockshield first, bear in mind it will want to spray everywhere like putting your thumb over a hose! Give the pipework a gentle tap with screwdriver or something! Then do trv side using Dec cap not trv head!

 

[magicmanalex]

BINGO!!!

Found the problem!

Firstly a MASSIVE thank you to Dilalio for his help.

I left the heating on, but being the chicken-s**t that I am, I removed the decorator cap on the lockshield valve and attached a braided filling loop hose to it. Pointed that into a bucket and opened the valve. Got about 75ml of warm, reasonably clean water out. Then it stopped.

Figured that although I believe the lockshield side to be the return side, I should still have got some continuous flow out of it? Confused at this point.

Capped it and connected the hose to the TRV side. Nothing. Not a drop. Gingerly removed the braided hose and nothing came out of the TRV. Seemed clean and fine inside. Then I had a look at the wall (picture 1). Bit of loose plaster that I VERY carefully chipped away.

And there you have it - a bloody great kink in the pipe! (Picture 2).

The girlfriend and I have never had this radiator on in the 18 months that we've lived here. We reckon the previous owners must have known it didn't work and didn't bother repairing it or mentioning it. Another lesson learnt - check EVERY radiator works when viewing a house - even in the middle of summer!

Ah well - at least I've found the problem. The boiler had cut out with a low-pressure error on the display (probably due to all of the water I've removed so that explains why the lockshield side stopped pumping out water).

Looks like there's no point trying to straighten this kink out. I reckon drain the whole system, snip it off under the kink and fit a 90-degree elbow (unless anyone can suggest anything else?)

 

[dilalio]

Ha! Looks like a coupling when he needed an elbow

You can do quite a few things with barrier pipe (plastic)... But that ain't one of them!

Plumbing eh! Never know WHAT you're gonna uncover

 

[magicmanalex]

You're not wrong there!

Elbow fitted, radiator is lovely and toasty now. Probably the first time it's ever worked!

(Slight leak where 10mm plastic pipe goes into TRV, but I 'll sort that separately (the plastic pipe and inserts can be re-used, right?)

Boiler's just locked out. Error code says primary pressure too high and the manual says to reduce central heating system pressure. (I believe this model has dual expansion tanks).

I filled it to the required 1.5 bar before starting it up and bled the new rad.

Should I just bleed the radiators some more?