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Discuss Single pipe system blocked ? in the Central Heating Forum area at PlumbersForums.net

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single pipe system pipework blocked ? System is 7 rad single pipe in a bungalow fed by Worcester combi boiler. After many years of being hottest house on earth rads are struggling. Service engs [ same ones for many years] have changed pump , cleaned with sentinel 800 [ though i don't believe it was carried out correctly with regard to correct flushing / draining ] They believe the pipework is fouled and have recommended a full system pwk change to a 2 pipe system , obviously at considerable cost. The system is in my mother's house but I've spent some time there and carried out following trials.........Left system running with a single rad on line for 30 mins , repeated for each rad in the house. Every rad heated up fully. To me this means there is some sort of route thru all the system pipework. The engineers have agreed to carry out a further wash at reduced cost but following job method that I have supplied them from both Sentinel and Fernox , may use a fernox product this time.............Any thoughts ?
 
if you have altered the lock shields then you have to re balance the whole system,
water goes the fastest way it can, so it will pass the rads return to the boiler, then your rads don t get hot,
you need some one who knows the job.
 
To flush that they would need to take the rads out one at a time and clean them outside with a hose or similar method in my opinion.
I obviously cannot say for certain as I haven't seen the job but an engineer on site should be able to tell if the pipework is blocked without guessing.
 
if you have altered the lock shields then you have to re balance the whole system,
water goes the fastest way it can, so it will pass the rads return to the boiler, then your rads don t get hot,
you need some one who knows the job.
I've looked into balancing issues and initially ruled it out as no individual rad is getting excessively hot , 6/7 rads have TRV'S fitted and 3 rads are turned fully off all the time so even though I'm not sure of order of flow I would be surprised if this was the issue.
 
To flush that they would need to take the rads out one at a time and clean them outside with a hose or similar method in my opinion.
I obviously cannot say for certain as I haven't seen the job but an engineer on site should be able to tell if the pipework is blocked without guessing.
rads don't seem an issue as fully heating up when lined up individually.
 
Look up one pipe systems the normal pipe up is top bottom and trv’s should Be full flow
 
Look up one pipe systems the normal pipe up is top bottom and trv’s should Be full flow
thanks for your help , will have a chat with engineer when he comes but i'm unaware of any changes made since system was working perfectly so can only assume design and hardware are not an issue.
 
If all was working well once, it is now almost certainly a balancing issue.
As I understand it a balancing issue is where individual rads take lions share of hotter feed , normally at the start of the loop , leaving other rads further downstream to be fed with cooler water. Surely if this was the issue at least 1 rad would be excessively hot and this is not the case.
 
Or on a one pipe too much heat goes straight back to boiler - think of the boiler as being your ‘one excessively hot radiator’.
 
You possibly have a one pipe system relies on gravity normally to heat up each rad that why they are top entry bottom exit if your TRV’s are not full flow there is one restriction, you have probably messed with the lock shields so system is out of balance, what pump speed have you set it at it may be going too fast to allow flow into the radiators.

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all the rads are and always have been bottom entry and exit as diagram 2. My understanding is the flow thru rads is driven by combination of convection and differential pressure as whenever a flow is present in a pipe the pressure down stream will always be lower. I stand to be corrected but it would seem balancing the system is just about getting even / efficient heat distribution from each rad in the system.
 
You’re clearly the man for the job, I expect you’ve fixed it by now.
if it had been my house i'd have probably f****d it up altogether by now ha ha. As it's my mother's i'll leave it to the professionals , mind you i have now supplied them with job methods from sentinel and fernox for chemical clean and will be in attendance to make sure it's followed.
 
I haven't read the entire thread in forensic detail :) but I can't see the part where you checked and ruled out the boiler heat exchanger. That's where the narrowest channels in the system are likely to be found. Is there a filter? If so, how much crud was in it. If not, that may be your problem.
 
I haven't read the entire thread in forensic detail :) but I can't see the part where you checked and ruled out the boiler heat exchanger. That's where the narrowest channels in the system are likely to be found. Is there a filter? If so, how much crud was in it. If not, that may be your problem.
no filter at the moment , will get 1 fitted if / when replace all pipework , eng coming back 19/2 to carry out repeat chemical clean so will ask him about exchanger then.
 
like i said balancing issue right at the start. its a pain in the but to sort some times done 2 last year.
 
like i said balancing issue right at the start. its a pain in the but to sort some times done 2 last year.
Still can't understand how it's a balancing issue as no radiators are " over heating " ie robbing the others. I can see how you can balance the rads to share heat output but without valves in the pipework circuit what other " balancing " can you do ? can you explain your theory / potential fix.
 
Still can't understand how it's a balancing issue as no radiators are " over heating " ie robbing the others. I can see how you can balance the rads to share heat output but without valves in the pipework circuit what other " balancing " can you do ? can you explain your theory / potential fix.
God help the plumber on this job.
 

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