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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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CH System Design/Overhaul/Maintenance.
This is a long rambling post for which I apologize, but If I just come
in with some questions there will inevitably be requests for more info so I have tried to include all relevant info in one post. As some of you will be aware I am helping a friend who has inherited a house needing lots of updating. The central heating being one such component. The system was designed and installed by the now deceased owner who helpfully kept lots of notes. There are extensive notes on maintenance/repairs and changes from its installation in 1976 until about 2005, but no record of any work since 2005. I'm sure that in its heyday it was well maintained but that very little will have been done to it in the last ten years. As of now the DHW works fine (if somewhat uneconomically) but the room heating system is completely broken, taking several hours to increase the house temperature by a couple of degrees. The radiator temperatures never get much above "slightly above cold", and by feeling the water temperature around the CH pumps and comparing to the DHW pump I am sure that there is very little water circulation round the radiators. At the end of the heating season I intend to drain, remove all radiators, flush, remove pumps and assess but before I even start I want to make sure that I fully understand the system and make sure that I take the right course of action. (It might be time to remove all active components and start again - although this would probably be beyond my DIY skills -but at least if I understand the system I can have an intelligent discussion with a professional). Having looked at the DIY FAQ pages what I think I have is an "S Plus Pump Plan" ie exactly what we have here http://wiki.diyfaq.org.uk/index.php/...s:_S_Plus-plan but with the zone valves replaced with pumps and what he called "clack valves" (of which more later). The control system looks like a home brew box of relays and diodes. Perhaps some pictures would help. (control box links lower down) https://www.dropbox.com/s/vgvvcdyxlm...ntrol.jpg?dl=0 https://www.dropbox.com/s/4zrocgzq81...nstrs.jpg?dl=0 Now to my mind the radiators are not getting warm because 1) They are blocked - removal and off site flushing should solve this. 2) The pumps aren't pumping - they are either A) blocked or B) not spinning A) Blocked - I have found info on diy faq about stripping and removal of corrosion products from the impeller (more time consuming but cheaper than a simple swap - time is not an issue). B) Not spinning - How do I tell? - Simple 1:1 replacement may be difficult see below. 3) Some other blockage. Now this is where we come to the "clack valves". Or to give them their correct title "Null Flow valves". (Leaflet courtesy of his extensive records) https://www.dropbox.com/s/5qxmapfy1s...valve.jpg?dl=0 There is a record of one of these jamming open causing " the landing radiator getting hot when only the DHW pump was running". It was stripped and rebuilt. I can see from the "S Plan plus pump" schematic that if you replace the zone valves with pumps then when only one pump is running there is nothing to stop back-flow in the other loops. Can these jam shut? I'm afraid google has not been my friend and I can find no reference to "clack valves" in modern heating systems. The only reference to NRV seems to be in relation to those fitted to incoming mains supply pipes. If these are jammed shut I can find no on line replacements. The chances of getting an overhaul kit for these valves today must be just about zero. Also the control box seems to be an aladdins cave of relays and diodes. Failure of one or more of these components is of course a possibility. https://www.dropbox.com/s/zm6ung9y1u...rnals.jpg?dl=0 https://www.dropbox.com/s/ksj3mh8wv7...x_pcb.jpg?dl=0 https://www.dropbox.com/s/sae3oudvgb...iring.jpg?dl=0 As far as I can see the design of the control box necessitates mods to the pump wiring circuit board. https://www.dropbox.com/s/wqdjodrxnh...tions.jpg?dl=0 It has taken me days wading through loads of old notes (note all images are of his notes, I have not created anything new), would this system be bread and butter to a current plumber/heating fitter or would they throw up their hands in horror? In the interests of future maintainability is it time to consider replacing the 3 pumps with one, removing the "clack valves", installing three zone valves, upstairs and downstairs programmable thermostats and doing away with the magic control box box of relays and diodes? (Although this will probably be a job for a professional rather than me) This wont be started until the end of this heating season but any help welcome. -- Chris B (News) |
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