Diagram of Primatic cylinder

[dmccormick]

Does anyone have a really detailed diagram of how the inside of a Primatic cylinder works. I've looked all over the web and seen a few schematics, but they don't really detail all the connections to see exactly how the air bubble seal works. Reason for asking is I am about to drain down a system and am concerned there might be some special sequence of events needed for refilling to ensure the air bubble is formed again.

 

[kevplumb]

just fill and vent as per

 

[corgigazza]

dont forget primatic only works on gravity hw have seen some converted to fully pumped that does not work.

 

[bripl]

do a search on elson units they had a form of primatic hot water which was pumped,drain them and fill them the normal way

 

[PEDANTICVINDICTIVEMAN]

Yea, been to one or two fully pumped primatic systems, never understood how they got away with it.

 

[MANDATE]

If you search this forum you'll find quite a bit on the 'primatic' look around Jan 2004. You won't have any problem, water has to rise in an inverted cone and overflow into a vertical pipe to fill the heating side. That is why you don't have two water cisterns and why you can't add additives. The air bubble is formed within the cone.

 

[dmccormick]

Thanks MANDATE,
Based on your description I've put together how I think it looks like:

I can also see if the air somehow goes, how the water can mix so additives are not great.

What I want to do though is try to clean the system to stop the boiler kettling and was planning to use Fernox Super Concentrate boiler restorer, before I found it was Primatic.

However, if the Fernox is only in for an hour and then the whole system flushed out I think that would be OK.

 

[kevplumb]

by jove i think you got the drawing spot on

if you are going to treat the system dont forget the cyl hold a lot of water and its not really the done thing chap

 

[MANDATE]

See www.purimachos.info/faq.htm

 

[DP]

The system will gas during the cleansing operation. The is no gurantee the bubble will not be displaced in the specified hour. Chemicals have to stay in the system a lot longer to disolve the sediment into suspended water. Quick 'hpur' fix may not do anything for the system.

 

[ChrisR]

Small but vital difference in an actual primatic - the upper pipe from the CH systemhas a sticking up bit inside the cylinder turned over at the top and open ended, so that "air" coming from the boiler up that pipe can escape without pushing the bubble out.

 

[dmccormick]

If I replace the cylinder with an normal indirect one and add a new F&E tank where do I connect the feed and exp. pipes. I am presuming the feed could tee into lower pipe of the cylinder coil and the expansion into the upper, but does it make any difference or do they have to go down to the boiler ? (Chris, my book hasn't arrived yet, hence the Q).

 

[PEDANTICVINDICTIVEMAN]

Some primatic types have an air vent on the side about halfway up, they always seize up and snap off causing aggro.

 

[bobb]

If I replace the cylinder with an normal indirect one and add a new F&E tank where do I connect the feed and exp. pipes. I am presuming the feed could tee into lower pipe of the cylinder coil and the expansion into the upper, but does it make any difference or do they have to go down to the boiler ? (Chris, my book hasn't arrived yet, hence the Q).

I have just taken out my primatic and replaced with a conventional indirect cylinder. Instead of a F&E tank I made a sealed by putting in a expansion vessel, gauge and filling loop. I first checked that my boiler could work on a sealed system.

 

[ChrisR]

... which is probably a simpler job!

The feed can go to the lower cylinder connection (usually) but the big pipe - the vent - can't go off the top one unless you keep the HW gravity heated. You can't have anything like a pump or valve in the line from the boiler to fresh air over the f&e tank. It can be a nightmare trying to find a way for a vent pipe!