Baxi bermuda with no separate feed and expansion cistern

[will77t]

We have a baxi bermuda that has been in the house for thirty years and has given up the ghost (needed a new valve that's no longer available). What seems very odd is that the system is gravity fed with a pumped radiator circuit but it has no separate feed and expansion cistern.
I'm guessing that the cold water cistern (for the hot water) is feeding the radiator circuit (the joint must be hidden somewhere as I can't see it in the loft or any accessible point) but the mystery of the open vent for the radiator circuit is even more bizarre:

The vent for the hot water comes directly from over the cold water cistern, right down to the top of the cylinder where it branches off. This is ofcourse how it should be, but I figure the radiiator circuit must also be joined to this at some point for venting the radiator circuit (as it doesn't seem to vent elsewhere and doesn't go to a separate feed and expansion cistern).

Can anyone tell me if they've come accross this before? It would go some way to explaing why the hot water is a rusty colour when you fill the bath to the top (from the immersion heater) - the two systems are combined. Was this the norm in the '70s?

Any Help would be appreciated.

P.s. I've bought an old replacement baxi bermuda 45/4m to get us through winter after which the house is going to be knocked around a fair bit and a whole new system will be commissioned. The only thing is, it's worrying me how this sytem ever functioned. The gravity feed for the cylinder isn't great, you'd assume that the cylinder should be directly above the boiler but it isn't - it's behind the boiler (about a foot higher) and the whole gravity circuit is about two feet from top(where it goes into the cylinder) to bottom (where it goes into the boiler). Obviously it did work but the replacement boiler has even less opportunity for gravity feeding (the distance from the inlet/outlet of the boiler is about 20cm less the the existing one.

p.p.s obviously I'd have the system checked before using it, but I don't want to waste my time connecting it if it's going to be pointless and/or dangerous.

 

[gas4you]

Sounds as though you may have a primatic cylinder. It will say on it somewhere.

Chances are that if this is as old as your boiler it has probably had it as well.

I assume you must be fitting the new bbu your self as this would not be allowed under current regs and no reputable installer would do it for you

 

[twgas]

sounds like it may be a fortic cylinder, it keeps the heating circuit seperate from domestic by air bubbles. not fortic-primatic

 

[will77t]

It says that it is a Newmatic Self priming cylider if that helps!?

 

[gas4you]

It says that it is a Newmatic Self priming cylider if that helps!?

Thats it, a primatic.

 

[will77t]

So how does this work then? As for fitting, I'm armed with a manometer and the installation manual, I know the Corgi checks and (until I came across the problem of having no spearate feed and expansion cistern) thought I was competant and knew what I was doing. I realise by asking on this forum about this problem I've seriously underminded my position on competancy.

So, is it safe to fit and how does it work? The current sytem has one feed and one return from the existing boiler. The installation manual suggests having two flows (one to the radiators and one to the gravity fed cylinder) with a pumped return and a gravity retun (underneath the pumped retun) going into the boiler. This is obviously not possible with my system.

Will I be alright to fit just the existing flow and return (although this will be a departure from the installation manual) given the ever decreasing gravity flow), or am I simply wasting my time.

Thanks again!

 

[gas4you]

Unfortunately whilst I am prepared to give general advice, I cannot knowingly instuct/help anyone who is not proved competent by the gas industry to fit a gas appliance.

Sorry.

 

[twgas]

i think you're wasting your time, if you have electric immersion use that for h/w, and beg/steal or borrow a couple of elec rads/fan heaters for now

 

[will77t]

Yeah, we've tried the electric heater option but not only is it costing us £300 for electricity per month, the house is getting mouldy. Now I can undertstand the position of a qualified plumber condoning unqualified installation but it is not against the law to fit your own boiler if you are suitably competant. I can also understand that in asking this question my competancy comes under scrutiny, so in this instance I shall say that a registered and qualified plumber will be installing this boiler. Given the above synario, would it be possible for him/her to simply fit the existing flow and return pipes or would he need to do something else. And, for simple curiositys sake, how did these old systems work without a spearate feed and expansion tank?

 

[gas4you]

Click HERE

 

[will77t]

Thanks Dave,

As it goes I've just found that page myself - I can't tell you how happy I am. I really thought I was going mad. It kept me awake all night thinking about it. I even climbed into the loft at 4am to see if there was something I'd missed because I couldn't sleep. Thank god it now all makes sense.

Hooray!!!

Will

 

[will77t]

But.....Given the above synario, would it be possible for him/her (the plumber) to simply fit the existing flow and return pipes or would he need to do something else.

 

[will77t]

And would the new gravity feed be sufficient as it's not very much higher than the boiler itself.

 

[will77t]

... and how would he test how the primatic cylinder is functioning correctly or (as I suspect) it is leaking into the cylinder.

 

[denso13]

Difficult to say without seeing it, let your plumber see it and advise you from there.