Freezing 3yr old son's bedroom HELP!

[smglasgow]

Hi

Moved into a property last year, combi system installed 3-5 years ago. Ready to start ripping radiators out as heating system is doing my head in with hours spent trying to resolve an issue with poor rate of heating on 2 radiators and a 3yr old encased in ice most mornings as a result! Apologies for the length of this post.

Got a 16 radiator combi system in bungalo (2 levels, 10 rads downstairs and 6 upstairs). Vokera Compact Combi 35HE model (35kw). Every rad has TRV and Lockshield (Danfoss RAS-C2). System heats fine, delivering flow temp of 75 and return 55 at the boiler when system up to full temp within 30-60min. House is 2 pipe flow and return system with rads brancing off it, but there appears to be two (or more) loops - once downstairs and possibly 2 upstairs (feeding bedrooms to front and rear of property respectively). Got a HIVE thermostat controlling the overall system located in an area in the middle of the home with adjacent ratiator TRVs set to 5).Finally, rads are all rated around 1.25KW at 80 degrees and are the designer range (look like old school rads with open tubes if that makes sense)

Problem arises on 2 radiators (front lounge and bedroom above it, which is 3 yr old's room). Both are at the farthest point from the boiler at the end of the lines (which I think is the issue here) and both refuse to heat beyond 55-degrees (measured at top middle of radiator using an infrared thermometer) after heating on for a couple of hours. If I leave heating on for a long time, like 4 hrs, the bedroom radiator will slowly warm up to ~60degrees.

Problem is in mornings when heating comes on at 6:30 am, kids get up at 7:30 and 3yr olds room is still like an icebox with radiator barely warm (same applies to front room downstairs) - perhaps reaching only 45degrees after an hour. This is despite the inlet pipe to both radiators being hot to touch (around 65-degrees after 30-min I would estimate). All the other radiators in the house come up to 60-65degrees temp quickly, but these two are just hopeless and result in 2 really cold rooms in the mornings. I know I could start the heating at 4am to ensure 3yr old room is toasty come 7:30 but that's just daft.

What I have done so far:

#1 added fernox to be on safe side, but water is clear and no sign of gunk when I bled all radiators (very little air in system - also checked all lockshileds and TRVs worked fine by removing trv and moving pin up and down in the case of the latter);

#2 removed all TRVs and opened lockshields 100%, turned room thermostat to 30-degree and blasted heating for 2hours - max temp in problem rooms 50-degrees;

#3 started balancing the system by closing down the lockshields progressively until 1st rad in the system was 25% open, leaving both problem radiators FULLY OPEN at locakshields re-ran test: max tem 55-degrees in problem rooms after 2 hours;

#4 closed down lockshields on radiators downstairs even further (apart from lounge) which has has little effect on lounge or 3yr old bedroom;

#5 Closed all radiators apart from lounge and 3yr olds room and ran heating - again despite hot inlet pipes to rads, they only heated to 55-degrees after two hours;

Observations.

#6 CHecked pump is working - 3 stage pump and set to each speed noting change in speed (audible) therefore assuming working OK,

#7 3yr old's brothers room which is the 2nd last in the line, is roassting with radiator hitting 65 degree temp in 30-60-min and after 2 hours there is still a clear 10-degree difference between them. Turnng off this radiator, which is like 8 ft away throught the partition wall from his brother does not improve the heating rate of the 3yr olds radiator one jot;

#8 problem radiators have good temp profile - hot at top and probably 5-10 degree difference at bottom, so I dont think they are sludged up and bled water is cystal clear.

Current thinking on possibilities:

#8 Pump is actually failing and not got enough power to push heat to 2 radiators at the end of the line;
#9 Got a blockage/restriction in the two problem rads (could be sludge, dodgy TRV pin, lockshield or airlock);

Regarding 9, what are the chances of both radiators having the same blockage issue. Too much of a co-incidence that they are each at the end of their respective lines in my view so I question whether a blockage is the issue - that said, the inlet pipes are roasting with the outlet pipes warm (Im seeing 20degree temp drop over the inlet and outlet pipes on these rads);

Airlock - could I have an airlock in both rads? Surely this would prevent ANY heating of the rads Vs what I am seeing,i.e., just not heating enough.

Any thoughts, suggestions for further tests I could do or solutions would be gratefully received. spent hours on this and still have a cold 3yr old bedroom in the morning and a inhabitable lounge! Current snowy conditions makes solving this a priority.

 

[ShaunCorbs]

turn all the other rads off except the two that are cold, turn heating on do these two rads get warm?

 

[Ch4 plumbing]

turn all the other rads off except the two that are cold, turn heating on do these two rads get warm?

Yep the OP did that ref #5 Shaun.

Just because the pin in the TRV moves up and down doesn't mean its fully open, it may well just be partially open.

How did you add the inhibitor?

 

[smglasgow]

fernox f1 express - inhibitor added at boiler fill pipe as per fernox's online video instruction.

p.s. thanks for replying guys

 

[REDSAW]

tbh, what time you have tried and spent on. would it not be better getting someone in with the apppropriat knowledge.

it would take me less time to sort it than type up a reply a full explanation.

couple of pointers though, you cant ballance rads if ones hotter than other, your sons 65deg is fed from the 3 year olds and starving the heat. try turning it off and your bedroom too!

 

[smglasgow]

Noted re the pin moving doesn't prove its fully open, but what are the chances both rads on different loops would have the same issue? The key here I am sure is they are both at the end of theirs lines and farthest from the boiler. I will however have a look and compare how far out the top of the valve the pin sits on "good" rads Vs these ones.

 

[Geyser]

Have you taken head off and checked the flow direction on the Danfoss trvs and locksheilds open?

 

[smglasgow]

I concur that I need an expert now, father in law is ex heating engineer and he spent today looking at this and has come to the conclusion we need to remove the rads and flush them outside - not ideal in current snow and -3degrees! Anyways, I did try turning all other rads off to prevent heat being stolen from 3yr olds room, but radiatior perfoamce was unaffected, still maxed out at 55degree cf others at 65 (when on).

Given your knowledge, do you think an airlock could be the isuue or would that result in a cold rad with no heat whatsoever.

If you know a good heating engineering in glasgow I would welcome a referral!

 

[smglasgow]

yes, done it on all 16 and confirmed flow direction or changed them to the right setting. Previous installer (before i bought) obviously didnt know how to set these up or balance the rads as all fully open bar one in the middle of a run!!!!

 

[REDSAW]

ok, is the rad cold in middle bottom?

 

[Geyser]

What pipe is it to rads? 10mm plastic by any chance.

 

[smglasgow]

radiator profile is pretty uniform with bottom 5-10 degree cooler than top, but no cold spots

 

[smglasgow]

15mm diameter pipe to radiators and yes, plastic.

 

[smglasgow]

identical to his brothers set up which operated perfectly, and is 8 ft way, hence my confusion!!!

 

[REDSAW]

not blocked then

 

[doitmyself]

#2 removed all TRVs and opened lockshields 100%, turned room thermostat to 30-degree and blasted heating for 2hours - max temp in problem rooms 50-degrees

I assume you mean the rad temp was 50C, not the room! The result does not surprise me at all as you have completely unbalanced the system, so rads nearer the pump will get more than their fair share of the heat.

#3 started balancing the system by closing down the lockshields progressively until 1st rad in the system was 25% open, leaving both problem radiators FULLY OPEN at lockshields re-ran test: max tem 55-degrees in problem rooms after 2 hours;
#4 closed down lockshields on radiators downstairs even further (apart from lounge) which has has little effect on lounge or 3yr old bedroom;

#5 Closed all radiators apart from lounge and 3yr olds room and ran heating - again despite hot inlet pipes to rads, they only heated to 55-degrees after two hours;

You need to check the two problem rad individually; i.e turn of all the other rads but the one you are checking.

Basing the results on the temperature in the middle of the rad is not accurate enough. It's the temperature differential of the radiator's flow and return pipes which is important.

Be careful using IR thermometers as they can give false readings, e.g if pointed at unpainted copper pipe they may read 50% low. Hold them as close as possible to the surface measured.

What speed setting is the pump on?

With all TRV heads removed, measure the flow/return temperature differential of all rads. If the results vary by more than one or two degrees the system is not correctly balanced.

 

[smglasgow]

hi doitmyself.

I know the limitations of an IR THERMOMETER and have also recorded inlet and outlet temps at each radiator in the system (have excel sheet with data representing hours work). I use black tape on the copper pipe to get more reliable reading. Top of rad (white surface) is reasonable indication with IR thermometer.

Re your other points,

Pump speed was originally on speed 3, have reduced it do speed 2 after father in law's visit and his insistance speed 3 was not needed!I see no change in the system temps at speed 2.

I have turned off all rads except the ones causing the issue, again a marginal temp improvement but no where near the target temp of ~65 at top of rad. For ref, the rads giving the problems are dropping 20-degrees C between inlet and outlet pipes.

Water I have drained off is so clean and rads are not cold at bottom so i dont think i have gunked up radiator. I also, in response to an earlier poster, checked the thermostat pins, problem rads have pins which stick out the same amount at the pins on TRVs on rads that work fine, and are free to move up/down, so again doubt that is the issue. The lockshields are also fully open.

tarting to think i might have a problem in the pipework between son #2's rad and the problem rad in my sons betroom (8ft away) but looking at the pipe in the attic there are no kinks in it and its a straight run.

Back to wondering if the pump has enough "oompf" to push heat to the last rads. Then again, the problem rads have inlet temps of high 60's just no flow through them.........

 

[smglasgow]

boiler pressure when hot.

Not sure if relevant, but I see a 1-bar increase in system pressure when the heating is up to speed. 1.25bar cold, rises to 2.25bar when hot.

 

[SimonG]

How far out the pins stick has nothing to do with if its working or not. Whats the temp of the pipework at the trv on the rads you have the issues?

 

[rpm]

Doitmyself, did you bother to read the complete thread before jumping in feet first? In particular post #1!

 

[smglasgow]

doitmyself: inlet is too hot to touch and IR themometer says mid to high 60's normally at inlet pipe and 20-degrees less at outlet. This is for a flow temp (at boiler of ~70) so only losing 5 degrees in the long run to the final radiator (upstairs and down). I have 2 rads with same issue recall.

Coming back to pump speed for a moment, is it common practice to set the pump at fastest speed on a combi system? Father in law has vented system and say pump doesnt do any work other tehn circulate and so setting at 1 shoudl be fine. He compromised at setting my system speed at 2 yesterday, but the system was originally going at 3. To my mind the pump speed determines a) flowrate for a given system pressure drop (resistance) and b) temperature difference between flow and return for a given set of radiator lockshield settings. If the system wont balance because all the rads only drop say 5 degrees then the flow is too high and the pump needs knocking down a speed. Conversely if all the rads drop 20 degrees even after opening the lockshields fully then the system needs more pump speed. On that, I understand I should be aiming for a temp drop of 12 degrees between inlet and outlets to each rad.

 

[stevetheplumber]

change the trvs

 

[SimonG]

Hurray. Common sense wins the day. The 3 year old is freezing and your discussing temp drops across a radiator. FFS.

 

[smglasgow]

starting to think this might by the issue right enough, even if pin is apparently freely moving up and down, as I have two other radiators on the system that will not "close" when I screw the TRVs down to OFF position (one past frost setting). Even taking the TRV heads off a pushing down the pins on those TRVs does not stop flow through the radiator. Once is on a towel rail so not concerned by that and the other is on a radiator close to the room thermostat and I leave that at FULLY open anyway (setting 5 on the TRV) - but does make me wonder about the quality of the supposedly excellent danfoss TRVs!

I take it to change the TRV bodies I need a full system drain down or pipe freezing kit! Think I will go with the former, re-dose fernox and replace all TRVs that are not fully closing (2) as well as the TRVs on the suspect radiators...........would you recommend changing the lockshields on the two problem radiators at the same time, to take them as a possible source of issue out the equation?

Still curious about the pump speed setting - any advice?

 

[SimonG]

Wiggle pins, not too hard, and tap trv with something heavy. Will confirm. As for pump speed, whatever it says in the manual. More than just the heating circuit to consider on a combi.

 

[PhoenixServices]

My two penny worth, some of these designer rads have baffles and should be piped up a certain way round. I.e flow to inlet. Had this before they don't perform as well. If rebalancing and changing trvs fail, flip the rad round and see how it performs.

 

[doitmyself]

I know the limitations of an IR THERMOMETER and have also recorded inlet and outlet temps at each radiator in the system (have excel sheet with data representing hours work). I use black tape on the copper pipe to get more reliable reading. Top of rad (white surface) is reasonable indication with IR thermometer.

You seem to be doing everything 'by the book'. Could you post the most recent results?

I see no change in the system temps at speed 2.

Interesting. Increasing the speed should produce a reduction in the differential, and vice-versa.

checked the thermostat pins, problem rads have pins which stick out the same amount at the pins on TRVs on rads that work fine, and are free to move up/down, so again doubt that is the issue. The lockshields are also fully open.

On some TRVs the pins are not connected to the plunger which blocks the flow, so free movement of the pin is not significant. Try giving the side of the TRV body some sharp taps with a hammer.

You say the LS valves are fully open, is this because you have balanced the system using the built-in balancer of the Danfoss TRVs?

 

[Geyser]

My two penny worth, some of these designer rads have baffles and should be piped up a certain way round. I.e flow to inlet. Had this before they don't perform as well. If rebalancing and changing trvs fail, flip the rad round and see how it performs.

Had this as well. Do we know what these designer rads are?

 

[PriestyUK]

Phoenix Services may have a point, I have also found on one job in a small-ish office block that 2 end rads didnt get very hot (one of which was the MD's office) We changed TRV's and radiators, we pulled it through on the drain cocks to make sure no air or $hit in the pipework and still the same problem. All the other rads got hot, it was only by chance that we thought lets just change the pump that it cured the problem. Pumped seemed to be running fine but some how it just wasn't man enough anymore to reach them last 2 rads whether the impeller blades had worn down I don't know but changed that pumped and MD was finally happy.

 

[Leo21]

You seem to be doing everything 'by the book'. Could you post the most recent results?



Interesting. Increasing the speed should produce a reduction in the differential, and vice-versa.


On some TRVs the pins are not connected to the plunger which blocks the flow, so free movement of the pin is not significant. Try giving the side of the TRV body some sharp taps with a hammer.

You say the LS valves are fully open, is this because you have balanced the system using the built-in balancer of the Danfoss TRVs?

You dont tap trv,s from the side. Specially not sharply, you tap them on the pin! Get your facts right before giving advise. Perhaps contact the mods with your qualifications, so we know your actually qualified to advise these poor unsuspecting people.

 

[Leo21]

Hi

Moved into a property last year, combi system installed 3-5 years ago. Ready to start ripping radiators out as heating system is doing my head in with hours spent trying to resolve an issue with poor rate of heating on 2 radiators and a 3yr old encased in ice most mornings as a result! Apologies for the length of this post.

Got a 16 radiator combi system in bungalo (2 levels, 10 rads downstairs and 6 upstairs). Vokera Compact Combi 35HE model (35kw). Every rad has TRV and Lockshield (Danfoss RAS-C2). System heats fine, delivering flow temp of 75 and return 55 at the boiler when system up to full temp within 30-60min. House is 2 pipe flow and return system with rads brancing off it, but there appears to be two (or more) loops - once downstairs and possibly 2 upstairs (feeding bedrooms to front and rear of property respectively). Got a HIVE thermostat controlling the overall system located in an area in the middle of the home with adjacent ratiator TRVs set to 5).Finally, rads are all rated around 1.25KW at 80 degrees and are the designer range (look like old school rads with open tubes if that makes sense)

Problem arises on 2 radiators (front lounge and bedroom above it, which is 3 yr old's room). Both are at the farthest point from the boiler at the end of the lines (which I think is the issue here) and both refuse to heat beyond 55-degrees (measured at top middle of radiator using an infrared thermometer) after heating on for a couple of hours. If I leave heating on for a long time, like 4 hrs, the bedroom radiator will slowly warm up to ~60degrees.

Problem is in mornings when heating comes on at 6:30 am, kids get up at 7:30 and 3yr olds room is still like an icebox with radiator barely warm (same applies to front room downstairs) - perhaps reaching only 45degrees after an hour. This is despite the inlet pipe to both radiators being hot to touch (around 65-degrees after 30-min I would estimate). All the other radiators in the house come up to 60-65degrees temp quickly, but these two are just hopeless and result in 2 really cold rooms in the mornings. I know I could start the heating at 4am to ensure 3yr old room is toasty come 7:30 but that's just daft.

What I have done so far:

#1 added fernox to be on safe side, but water is clear and no sign of gunk when I bled all radiators (very little air in system - also checked all lockshileds and TRVs worked fine by removing trv and moving pin up and down in the case of the latter);

#2 removed all TRVs and opened lockshields 100%, turned room thermostat to 30-degree and blasted heating for 2hours - max temp in problem rooms 50-degrees;

#3 started balancing the system by closing down the lockshields progressively until 1st rad in the system was 25% open, leaving both problem radiators FULLY OPEN at locakshields re-ran test: max tem 55-degrees in problem rooms after 2 hours;

#4 closed down lockshields on radiators downstairs even further (apart from lounge) which has has little effect on lounge or 3yr old bedroom;

#5 Closed all radiators apart from lounge and 3yr olds room and ran heating - again despite hot inlet pipes to rads, they only heated to 55-degrees after two hours;

Observations.

#6 CHecked pump is working - 3 stage pump and set to each speed noting change in speed (audible) therefore assuming working OK,

#7 3yr old's brothers room which is the 2nd last in the line, is roassting with radiator hitting 65 degree temp in 30-60-min and after 2 hours there is still a clear 10-degree difference between them. Turnng off this radiator, which is like 8 ft away throught the partition wall from his brother does not improve the heating rate of the 3yr olds radiator one jot;

#8 problem radiators have good temp profile - hot at top and probably 5-10 degree difference at bottom, so I dont think they are sludged up and bled water is cystal clear.

Current thinking on possibilities:

#8 Pump is actually failing and not got enough power to push heat to 2 radiators at the end of the line;
#9 Got a blockage/restriction in the two problem rads (could be sludge, dodgy TRV pin, lockshield or airlock);

Regarding 9, what are the chances of both radiators having the same blockage issue. Too much of a co-incidence that they are each at the end of their respective lines in my view so I question whether a blockage is the issue - that said, the inlet pipes are roasting with the outlet pipes warm (Im seeing 20degree temp drop over the inlet and outlet pipes on these rads);

Airlock - could I have an airlock in both rads? Surely this would prevent ANY heating of the rads Vs what I am seeing,i.e., just not heating enough.

Any thoughts, suggestions for further tests I could do or solutions would be gratefully received. spent hours on this and still have a cold 3yr old bedroom in the morning and a inhabitable lounge! Current snowy conditions makes solving this a priority.

Ufortunately there's a flaw in our system on here, please only take advise from members with gs registered, plumbers arms or trusted badges.

 

[stevetheplumber]

actually leo i find a sharp tap on the side works the best tapping the pin is pushing the valve shut i use the handle of a spanner

 

[Leo21]

Thanks for that Steve, give him ammo.

 

[smglasgow]

Just a quick thanks to all who have contributed, much appreciated.

Answers to least couple of points:

- no markings on rads to show what model, but I suspect they are STELRAD CLASSIC, 3 COLUMN DESIGN based on what I see online - how do you know if they are directional as one poster commented?;

- I dont want to inflict data from an excel sheet on everyone, so inclined not to try and post that lot doityouself!

- sharp tap to side of TRVs interesting idea - Ill stand by with a bucket just in case......and as per latest post, inclined to use handle of hammer then if brave ramp up to using the head!

DOITYOURSELF COmment "You say the LS valves are fully open, is this because you have balanced the system using the built-in balancer of the Danfoss TRVs?"

- Not sure what you mean by built-in balancer. but l said LS valves are fully open as I took the cap off and unwound them using 6mm alan key to their furthest open position.

- Pump replacement is where I am heading if the hammer tap doesnt work, but as this would involve a drain down of the system I could also remove the problem rads and thoroughly flush, test lockshield and trv flow BEFORE installing new pump but basically have all the bits to hand should I need them: (Pump, 2 x TRVs + 2 x lOCKSHIELDS) then only install the pump and valves if I find the current ones work and it was indeed the rads that somehow were gunked up (yet they only have a 5 degree temp diff from top to bottom so doubt that) -Q then becomes what pump should I replace the existing Vokera 35HE pump with - same or beefed up?

Final thought is I have airlocks, and no one has yet confirmed if an airlocked radiator can get hot,just not REALLY hot or if it would always be stone cold.

 

[joni os]

actually leo i find a sharp tap on the side works the best tapping the pin is pushing the valve shut i use the handle of a spanner

Hold block of wood on opposite side to focus effect of tap.