Central Heating Confusion

[loffler]

I recently bought a house and would like to change the radiators, but cannot put my finger on exactly what kind of system it is to be able to drain and refill it.
I have a potterton kingfisher MF RS 50 boiler downstairs and an emmersion tank upstairs. The only tank in the loft is the large cold water tank, no feeder tank. The only thing by the boiler is a pump and a drain valve, but cannot find a filling loop or expansion vessel anywhere.
All the radiators only have one vale one.
Basically, I believe the system to be some kind of open vent system rather than a gravity or sealed system, but need verification as I have to drain the system to remove the rads.
If this is correct, where does the expansion go, if no feeder tank or vessel?? Is there a vent pipe going into the cold water tank in the loft? How would I add cleaner/corrosion additives to this kind of system as there is no header tank to add it to??
I hope this makes sense - if you need more info, just ask.
Thanks

 

[kevplumb]

sounds like a primatic cylinder

if it is you can't add anything

 

[JohnD]

Have a careful look at your hot water cylinder (pull the insulation aside). See if it has any labels on it. If not, tell us many pipes go in and out, and where they are.

edited: Too slow again

 

[MANDATE]

I'd go along with Kev.
I have a primatic cylinder, must be 32 years old.
No header tank. It's not sealed so no filling loop or expansion vessel.
It is filled from the large cold water tank
Cylinder contains inverted type funnel that creates an air bubble when filling. The bubble separates the CH water from the HW water. You must NOT add any type of cleaner/addatives to this type of system.
Draining down no problem other than you have no HW while doing the work.
Try a search for primatic, it was the subject of some discussion two years ago.

 

[kevplumb]

 

[loffler]

Ahhhh, I see - it all makes sense now!
The problem that ive got is that im replacing one radiator with a heated towel rail and it states that it requires additives. What would happen if I ignored this and fitted it anyway? Would it just need draining every year or fail completely?
What are my options for replacement? Can I get a regular open vented cylinder and will that mean I will need to put an expansion tank in the loft??

Thanks for your help

 

[Agile]

Most people would recommend that you replace the primatic as they were never that wonderful and have been very troublesome for a few.

If you dont want to then the normal advice would be to fit a brass towel rail.

If you insist on using a steel one then it will not be covered by any guarantee but will be no better or worse than your existing rads.

Tony

 

[loffler]

Right, I have managed to drain the system and do the work I needed to do and am now trying to refill the system.
The downstairs radiators fill correctly without problems, but the upstairs are not filling. I am guessing this is something to do with the pump not being on. Do I have to do anything to the pump to get the upstairs radiators to fill correctly?? If not, how do I get the upstairs rads to fill?
The pump is a Grundfos Selectric.

Thanks

 

[Agile]

I would expect that a primatic cylinder should fill all parts of the system as long as the cold tank is in the loft without any problem.

Perhaps some of the older people on here might have experience of this problem.

Luckily they are a bit before my time!

Tony