Primatic cylinders

[Neil9834]

I have had a look and seen some posts related to Primatic cylinders in the past but I just thought that I would see if anyone can offer any advice.

Recently involved in a job with a Primatic cylinder and have ordered a new one to replace like for like. I've heard that the best way to fill these systems is by doing so slowly, are there any other pointers anyone can give?

Another question I have is, if you were, for instance to change the Primatic system for a conventional f&e system, where would be best to take vent from? My worry would be that I would take the vent off of the return near the heating feed at the cylinder and there is a motorised valve somewhere that would only allow the heating part of the cylinder to be activated when hot water is selected which as we know would effectively create a dangerous system because you would potentially have a system with no means of expansion when heating without hot water being in demand.

I'm not overly familiar with these systems so excuse my lack of knowledge. I just would like to understand it more for my own experience as I'm sure to come across them again through time.

Before anyone tries to shoot me down for being a diyer tinkering with things I have no business tinkering with I will mention that I am a plumber with ten years experience, I have fitted many cylinders, open vented and unvented as well as boilers etc this is just not a system I am all that familiar with and would just like a back and forth discussion about it to learn a bit more,

Thanks in advance

 

[fixitflav]

I have had a look and seen some posts related to Primatic cylinders in the past but I just thought that I would see if anyone can offer any advice.

Recently involved in a job with a Primatic cylinder and have ordered a new one to replace like for like. I've heard that the best way to fill these systems is by doing so slowly, are there any other pointers anyone can give?

Another question I have is, if you were, for instance to change the Primatic system for a conventional f&e system, where would be best to take vent from? My worry would be that I would take the vent off of the return near the heating feed at the cylinder and there is a motorised valve somewhere that would only allow the heating part of the cylinder to be activated when hot water is selected which as we know would effectively create a dangerous system because you would potentially have a system with no means of expansion when heating without hot water being in demand.

I'm not overly familiar with these systems so excuse my lack of knowledge. I just would like to understand it more for my own experience as I'm sure to come across them again through time.

Before anyone tries to shoot me down for being a diyer tinkering with things I have no business tinkering with I will mention that I am a plumber with ten years experience, I have fitted many cylinders, open vented and unvented as well as boilers etc this is just not a system I am all that familiar with and would just like a back and forth discussion about it to learn a bit more,

Thanks in advance

I'm surprised you can still get a Primatic, I thought they were obsolete.
Why would you want to put the open vent where you suggest? The usual arrangement is boiler - open vent - cold feed - pump. Then there is no trapped volume, whether there's a 3-port valve (W or Y plan) or 2 2-ports (S plan), whatever position they're in.

 

[ollski]

Yes slowly so you don’t blow air bubble out, but why bother with another primatic?

 

[fixitflav]

As I understand it a Primatic vents and feeds via the main CWST, so doesn't need a F/E tank. But I would still change to a conventional. For one thing, with a Primatic, inhibitor can't be used in the heating circuit, which IMO makes it a non-starter.

 

[Mike4]

Recently involved in a job with a Primatic cylinder and have ordered a new one to replace like for like. I've heard that the best way to fill these systems is by doing so slowly, are there any other pointers anyone can give?

Can you expand on why you need to replace it? For filling yes I'd fill it slowly, but not ridiculously slow. Fill the loft tank then say one-third open the gate valve in the cold fill. Don't do anything oddball like filling it from the CH drain cock.

If you change in to a conventional F&E system you'll need to fit an indirect cylinder not a Primatic, you realise that I hope? In whixh case just copy the pipework/pump/valve format you'll have seen in hundreds of 'ordinary' systems.

 

[Neil9834]

Hi there thanks for the replies. Main reason for sticking with a Primatic is simply not having enough knowledge on how the system has been piped with regards motorised valves etc so I was wanting to keep it the same to make it simpler for myself. I had toyed with putting an unvented unit in when initially looking at the job but there was nowhere to run the PRV safely.

With regards getting a Primatic cylinder yes I was pretty surprised that the supplier could get me one within a couple of days and the reason for my vent position was simply because it's the only access I had to the pipework.

When I fit the new Primatic I'll be sure to fill it slowly but im going to cut open the old one when I get it out to take a look and I will post it on here for anyone who's interested in the workings of it, mainly for people like myself who have never come across them before but any other tips for replacing it would be appreciated, just in case there are any knacks to making the installation easier,

Thanks again

 

[Neil9834]

I should have mentioned that the the Primatic that's in is a combination indirect cylinder. So no cold water storage tank, the combi fills both the hot water and the heating from the header

 

[Neil9834]

Sorry Mike4 It needs replaced because the old one is pinholed

 

[Mike the Boilerman]

I should have mentioned that the the Primatic that's in is a combination indirect cylinder. So no cold water storage tank, the combi fills both the hot water and the heating from the header

Eh? You've got me lost now.

The whole point of a Primatic is to have one single cold water storage tank feeding it, it being heated indirectly by some sort of gravity circulation boiler. There should not be any motorised valves on the system, they are not designed to be connected to a fully pumped system.

Why not just drain the old one and solder over the pin-hole? That's what I do with those occasional random pin-holes in cylinders, when the hole is accessible.

 

[Neil9834]

Never soldered over a pinhole before to be honest and don't really have time to try it and then have it fail and have to resort to replacing it anyway. There's a motorised valve on this system and a programmer on the boiler which allows you to select hot water or heating separately and I have read elsewhere that it is possible to have pumps on these systems but like I say, this is a new one on me and just looking to learn more about how they operate for future reference and also because I will be renewing this in a couple of days.

Just out of curiosity how does the heating water circulate ordinarily on these with no pump?

Thanks

 

[Mike the Boilerman]

Never soldered over a pinhole before to be honest and don't really have time to try it and then have it fail and have to resort to replacing it anyway. There's a motorised valve on this system and a programmer on the boiler which allows you to select hot water or heating separately and I have read elsewhere that it is possible to have pumps on these systems but like I say, this is a new one on me and just looking to learn more about how they operate for future reference and also because I will be renewing this in a couple of days.

Just out of curiosity how does the heating water circulate ordinarily on these with no pump?

Thanks

Soldering over takes seconds to do once drained down, which you have to do anyway to change the cylinder.

Primatics are designed for use with 'gravity circulation' primaries to/from the boiler. The water circulates by natural convection. Adding a pump risks corrupting or destroying the air bubble in the Primatic. You might get away with t but they are not designed for use with pumped primaries. Have a google and see if you can find manufacturers instructions for fitting the Primatic.

 

[Nige F]

Eh? You've got me lost now.

The whole point of a Primatic is to have one single cold water storage tank feeding it, it being heated indirectly by some sort of gravity circulation boiler. There should not be any motorised valves on the system, they are not designed to be connected to a fully pumped system.

Why not just drain the old one and solder over the pin-hole? That's what I do with those occasional random pin-holes in cylinders, when the hole is accessible.

Sounds like a Fortic Primatic

 

[Mike the Boilerman]

Sounds like a Fortic Primatic

I think you could be right there. A Fortic combination cylinder rather than a Primatic self priming single feed indirect cylinder.

People get them mixed up rather like they confuse combi with condensing...

 

[ianmcd]

I should have mentioned that the the Primatic that's in is a combination indirect cylinder. So no cold water storage tank, the combi fills both the hot water and the heating from the header

you do not have a primatic cylinder

 

[Mike the Boilerman]

you do not have a primatic cylinder

I'm also inclined to suggest the OP actually has a direct (rather than indirect) Fortic combination cylinder, given his comments about there being no other tanks. With an indirect Fortic there would still be a separate header tank somewhere to fill the CH circuit.

A photo from the OP would clear this up nicely....