Primatic cylinders

Fortic indirect Primatic cylinder
 

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That is a primatic cylinder with its own cold water storage tank (not an F&E tank).
 
If the CH can be pressured (sealed) with an expansion vessel then do it, replacing the Fortic primatic with a Foric indirect cylinder.
 
Well I got one from my supplier for about £400 which was only about £100 more than conventional combi cylinder. I don't have time to faff about and covert it and I just want the job done to be honest so I'm just replacing it like for like. The only advice I've had with regards these is to fill them slowly to allow time for the air bubble to form so if that's all there is to take into consideration than that's cool.

I would like to touch on something someone previously posted here though that Primatic cylinders work with a gravity circulation boiler. How does the water circulate without a pump?
 
Convection.

To explain in more detail, when the boiler heats the water inside it, the water expands do it's density becomes a little lower than the slightly cooler water in the pipework above. Put another way, the water at the top of the system becomes heavier than the water below so the cooler, heavier water falls down the return pipe into the boiler, and the hotter lighter water rises up the flow pipe to the cylinder heat exchanger, where it gives up its heat, cools and flows back down the return pipe to the boiler. It gets re-heated and the sequence continues until the cylinder reaches boiler temp and equilibrium is achieved. Circulation then stops.

As you can imagine, the motive forces moving the water are microscopic so large pipes are needed. 28mm copper is considered the minimum.
 
Put the £1k towards a combi;)
Many 32kW combis cost far less than £1,200 for a primatic cylinder, £1,200 to keep you back in the same position is madness. Ripping it out then fitting a new efficient combi is the best solution all around, providing the existing main cold water supply is suitable. Then a great improvement with greater value all around.
 
Ripping it out then fitting a new efficient combi is the best solution all around,
That is not always true

roviding the existing main cold water supply is suitable
Have to have that checked before making any decisions

Then a great improvement with greater value all around.
Quite a few people would disagree with you there, changing from the copious flow rate from a cylinder of hot water to the limited flow rate from a combi can require a change of life style. Especially when baths are part of the life style.
 
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