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.

 

[Leo21]

Remove affected rad and fit length of copper between valves, see what temp you get on the pipe
If flow pipe, temp copper pipe and return all get to same hot temp, then rad is the problem
If no better, points to a restriction in flow/return pipe

What he said.

 

[Best]

Remove affected rad and fit length of copper between valves, see what temp you get on the pipe
If flow pipe, temp copper pipe and return all get to same hot temp, then rad is the problem
If no better, points to a restriction in flow/return pipe

That only proves a rad is faulty if there had been no heat at valves or rad previously.
If the flow pipe to rad valve had been always roasting, then by doing your method all you are doing is extending the pipe without the rad being there to absorb the heat. So your temporary pipe will heat, but will prove nothing if there is a partial blockage in the flow or return pipes

 

[REDSAW]

lockshield open 1/2 turn will do!
i will revert back to my first post geeeeeeeeeeeeeeeeeeeeee

 

[jonnyswamp]

That only proves a rad is faulty if there had been no heat at valves or rad previously.
If the flow pipe to rad valve had been always roasting, then by doing your method all you are doing is extending the pipe without the rad being there to absorb the heat. So your temporary pipe will heat, but will prove nothing if there is a partial blockage in the flow or return pipes

Didn't realise the flow had plenty of heat or that the lockshield was fully open
I will write 100 lines
"I must read every post, before replying"
I was under the impression that rad wasn't getting hot quick enough, so suggested the link pipe to see if heat got there quicker

 

[Best]

Didn't realise the flow had plenty of heat or that the lockshield was fully open
I will write 100 lines
"I must read every post, before replying"
I was under the impression that rad wasn't getting hot quick enough, so suggested the link pipe to see if heat got there quicker

I am not sure myself, tbh. At 7 pages of posts and still going, I think it is hard reading. :smile:

 

[Leo21]

It can still be a partially blocked pipe with a red hot flow.

 

[Best]

It can still be a partially blocked pipe with a red hot flow.

Yes, only needs little more than a pin hole in a blockage letting hot water pass through a pipe

 

[smglasgow]

took a break from this problem as a- we had a temp swing of +15 degree here in Glasgow in the last week and so not so urgent as before and b- head was spinning fault finding. Consensus appeared to be that there was a blockage in the return leg from 3yr olds radiator. Whilst I have yet to investigate this further I would like to suggest an alternative cause of the poor heating on 3yrs olds rad as keep in mind the downstairs lounge performs just as bad as this upstairs radiator. To recap:

- 3yrd olds upstairs rad barely 55 degrees at top of rad after 2 hrs.
- brothers bedroom (8ft away) rad is 65 degrees in 30-min;
- all other (4 upstairs) rads 65degrees no problems;
- lounge rad same performance as 3 yr olds room - 55 max after 2 hours;
- hallway rad slightly better (warmer I mean but only high 50's) - hallway rad is on way back to boiler now;
- next rad in the line is 65degrees (as are remaining 8 downstairs rads on the way to the boiler)


Surely from the above it suggests the issue is with the pumping power of the grunfos UPS 15-60 pump? I have it set to speed 3 and no odd noises, appears to run fine and have confirmed no air in the pump by loosening the bleed screw.

Q - how do you KNOW if a pump is under-performing (ive read about trying to stop the impeller with a screwdriver, but that sounds a bit vague and what sort of force would you need to apply?

- The pump does get hot to touch but not red hot, its circulating 75degree hot water afterall so should never be lukewarm to the touch correct?

Q - if i replace the pump, would you suggest a fully system replacement or just head and would the new grunfos UPS2 be a good upgrade given the VOkera compact HE 35 is 5+ years old.

Thanks again for your comments and patience with my daft Qs

 

[gmartine]

After seven pages a lack of response probably indicates you have all the answers you're going to get so either take it or just wait for the next really cold spell before you panick again.

From memory you should completely replace the TRV's of the malfunctioning rads, ensure the rads (designer) have been fitted the right way around and finally if the system is clean have the pump replaced or you could call in a GS engineer which is what you should've done in the first place.

 

[smglasgow]

Thought I would provide an update on this one, as only fair given all the advise given to date. Currently running system with x400 sentinel in it before giving it a manual flush using mains pressure in a couple of weeks time.

What we found to date - 2 problem rads (slow to heat and not heating fully) off the wall and flushed outside, some muck but not excessive. £50 spent on new TRVs and lockshields on these rads and others, all to no avail. Flow and return both confirmed as not blocked and decent flow at rad (by removing rad and opening valve on the pipe tails). Rads confirmed as b-directional by manufacturer however interestingly swapping the TRV to be on the OUTLET of my son's rad did add 5-degrees to the rad temp (when rad was off I opened TRV and lockshield to see flowrate and was amazed at how much more flow through lockshield c.f TRV - originally on the oulet leg - gave). Thought, swapping them might be worth while and so it proved (gained 5-degrees) and of course checked the TRVs bi direction setting was set as outlet now.

I then re-balanced system with rads next to bioler closed even further from 1/2 - 1 turno open originally to 1/4 to 1/2 turn open now (tiny amount when you look inside one of the lockshields I replaced, but amazingly the rads still heated up quickly). These LOCKSHIELDS are nearly 5 turns to fully open! This also improved temps slightly. Slight worried the small aperture settings will furr up with gunk and so thinking about installing a magnaclean in due course or re-balancing with the pump speed at 2 to get increased aperture settings on the lockshields. Any thoughts?

Currently runnign the x400 more as precaution given 5 years old and only bought home 18m ago, but hopefully this plus a re-balancing of the system will address the issue (FOR MY SON AT LEAST). His rad is the last in the line upstairs. Unfortunately the front room rad (last in the line downstairs is still not great). Had reason to go under the floor for the 1st time since buying the home at the weekend and was surpirsed to see the downstairs rads are fed off a 22 manifold and all rund 10mm microbore!!!! U/stairs is all 15mm PVC.

All downstairs rads are fine except the front room, which is some 6m from the manifold on 10mmm microbore. The manifold feeding this rad is a JG Speedfit Inline Manifold 4 Port unit.

My Q is, would a 12 m loop, 6m there and back feeding a 1kw rad be OK on 10-mm microbore or shoudl I consider upgrading this pipe to 15mm to help get increased flow to this rad? The issue of getting heat to the rad has never been there - always high 60-s at inlet, just no flow through the rad so huge temp drop and little heat.

Before anyone says it, I know I could have got a GS engineer to look at this weeks ago, but this is now a point ot principal for me that I, with your help, will fix this!

Thanks as always for the feedback.

 

[Sparkgap]

All downstairs rads are fine except the front room, which is some 6m from the manifold on 10mmm microbore. The manifold feeding this rad is a JG Speedfit Inline Manifold 4 Port unit.

My Q is, would a 12 m loop, 6m there and back feeding a 1kw rad be OK on 10-mm microbore or shoudl I consider upgrading this pipe to 15mm to help get increased flow to this rad? The issue of getting heat to the rad has never been there - always high 60-s at inlet, just no flow through the rad so huge temp drop and little heat.

Before anyone says it, I know I could have got a GS engineer to look at this weeks ago, but this is now a point ot principal for me that I, with your help, will fix this!

Thanks as always for the feedback.

1kW should be okay on 10mm. Wondered if there might have been a problem with the pump not being man enough for the job but the change between 10 and 15mm in terms of pressure drop isn't a lot and if it's 22mm up to the manifold should be plenty. Just a thought, if you can get at the return manifold and check its temperature to see if there's any issues. Even more stupid thought: they haven't taken both F&R conns to the front room rad off the same manifold have they? I have seen it done....

 

[smglasgow]

Just checked and flow and returns are correctly plumbed at manifold. Measured length again and closer to 10m each way! Also noted none of the microbire pipework is insulated, so yet another to do job or is the heat loss through 10mm microbore not worth worrying about? Will be draining the sentinel soon, so could run a new 10mm returrn pipe to the prob rad, if a 20m loop is feasible on a 1kw rad. Thing just aint comin up to temp despite hot inlet, New valves and a flushed radiator (taken to garden with hose). Either blocked return or pump not up to the job I guess, but then it pushes water round the other 15 rads ok.

 

[Stigster]

Do you have access to the whole pipe run on the problem rad? Could the 10mm pipe have been pinched or squashed somewhere?