I will be changing my sister-in-law's downstairs living room radiator over Christmas. She has described the system to me over the phone and it is clearly the "Primatic" system where there is no separate feed and expansion tank for the boiler - the feed for both HW and CH comes from the hot water storage tank and the two systems are separated by a air bubble in the copper cylinder. I do understand the basic principle of this system but have never drained down and refilled one before. Question - if I drain down and refill normally will the air bubble reform correctly or is there a set procedure to follow to ensure this? I realise these are not fitted any more (since the mid 70's) but some of the older hands (no offence intended) might know. Thanks for any thoughts.
Cylinder will also drain so make sure the immersion is off, otherwise drain down the heating as normal then whats left in the cylinder. refill by opening the gate valve and leave a tap on till the water flows.
Hope this helps:- http://www.screwfix.com/talk/thread.jspa?forumID=25&threadID=10504&messageID=98386#98386 I ended up freezing the pipes, less hassle.
Thanks doitall. Yes I was aware that the cylinder would drain as well but I feared the bubble might not reform properly on refill. From what you say, this would be OK if I open a tap whilst filling. Unfortunately the CH system is 8mm micro bore so I may have other probs as well. Much obliged
Thanks bstyle - I looked at the thread - quite a coincidence having the same question asked a few months ago! Looks straightforward and relatively foolproof. On the question of freezing - I hate working against the clock after the "point of no return" and have no experience of the technique. I guess now might be the time to try though - its 8mm microbore so should freeze well! Thanks for replying.
Job should be easy, and like bstyle I would freeze as microbore has a habit of blocking up when you move the crud around, although good flush may be of some benefit. Interesting to note we never used 8mm in them days.
Thanks again doitall. I agree a good flush would be beneficial but would shy away from this due to the complication of the Prismatic and the airbubble. I suppose I could force mains water backwards through the system for a few hours then drain again. Thanks for your further comments.
Doitall - That's a thought. Sister in Law is having Xmas dinner at our place nearby so could leave it flushing for a good few hours through the newly opened 8mm pipes. Would have to nip in and fit the rad between party games! Many thanks again
used to have a primatic cylinder, a few years ago. The only advice that I could give you, is to fill the system slowly. The air bubble as i recall re invents itself, as the cylinder fills. if by fitting another radiator, the expansion, "cannot accommodate the expanding water" then the dhw and the heating side will mix. ( i think !!). funnily enough this is why i embarked on a plumbing course. i still work with plumbers who have this system in their own houses. Beggars belief in my experience. God i am going back a bit here, but did find that if the boiler is situated ni on directly under the cylinder things work out ok. Obviously it isn't fully pumped. and relied on stratification. OMG i dread the day i have to work on a system like that. The system that i used to have, was not a cylinder directly over a boiler, and had to pull out the thermostat, and it sounded like elephants running in the second floor, to expel the air. i'm sure you will succeed in your work. Please let me know how you get on. If you do struggle, please feel free to contact me, and i will try to help, but there are many a better plumber here than me. Good luck.
Hello doitall struggling with my bubble in the primatic tank.Have tried to re-establish it by draining the tank together with dhw and ch. Turned mains back on slowly,left a hot water tap open till starts to flow then switch tap off bled all radiators. Come to switch the pump/boiler on then can here the bubble burst via pipes/tank,eventually all rads heat up ... but still no hot water. Prior to draining sys to replace leakimg rad valve the whole sys performed very well. Can you please point me in the right direction presume i'm missing something. Thanks for any advice.
Hello doitall struggling with my bubble in the primatic tank.Have tried to re-establish it by draining the tank together with dhw and ch. Turned mains back on slowly,left a hot water tap open till starts to flow then switch tap off bled all radiators. Come to switch the pump/boiler on then can here the bubble burst via pipes/tank,eventually all rads heat up ... but still no hot water. Prior to draining sys to replace leakimg rad valve the whole sys performed very well. Can you please point me in the right direction presume i'm missing something. Thanks for any advice. Sounds like it as air locked inside the cylinder on the primatic flow (often happens). Really old primatics had an air vent built into the cylinder just above the primary flow - give his a try. If not,you need to boil the system up to shift the air bubble (expect a few bangs and cracks). Other than the above just keep using the system as normal and after a few days they usually work themselves out (the air bubbles).
Why all the panic Pete?? * What's wrong with you pups, do you think that because it's an old system(primatic) it was not well engineered? It's lasted this long without corrosion, has it not!! You need to turn off the gate valve, turn on a hot tap & also drain the CH. Do the alterations, turn off the DC on the CH, turn on the gate valve & slowly fill the cylinder untill your HW flows from the tap(it'll fill the cylinder quicker than the CH). Blead all rads as normal........Job done!!!. If you power flush the system, you may blow the bubble on the primatic, that can be re-established, no problem. You'll know when a primatic bubble needs to be re-established, the hot water will be brown, as the Primary & Secondary water have mixed. If you are still * doing the job, set another place for me at the Xmas dinner table and I'll do it. * [Edited by: admin6]
what you can't do with a primatic system is add inhibitor because of the risk of the bubble bursting and mixing with the hot water.
When I moved to this house in 1980 heating had allready been installed 8m/m and a primatic cylinder one of the first jobs I did is rip it out, bigger cylinder installed and f&e put in.
Hi all, could someone give me advice please, I have been informed that a old customer has there heating conected into there primary's like a more conventional system, I was under the impression that this couldn't happen as the pump would blow the air gap out? Any clarity would be great fully appreciated.
hello Harro, I'm not quite following yer, Its normal to have pumped heating, that's the only way it can work and it won't blow the bubble away although sometimes when you drain down and refill airlocks in the system can conflict with the bubble and cause mixing of the waters, this can result in dirty domestic water for a time, That's one reason sentinel and fernox don't like thses babys because its not recommended you put addatives in, this really annoys the 'peckham water' brigade as they see these systems as a fly in their ointment, if enough people have these systems running without addatives , it might lead to people thinking that they DONT need addatives, Lord preserve us
Thanks Tom, I have now checked over the install and it's how it should be, the information that I was given was the pump was connected directly on to the primaries so I had to question myself if this was ok. Thanks again on the advice
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