Pressurised central heating

[markyuk]

A couple.of questions on pressurised heating system. Can some one tell me where in the system the pressurised cylinder goes does it matter if it's on the hot feed or the cold return ? If on hot does it need to be before any rads ?
Moved in to a bungalow and just want to get my head round it all . Also with a pressurised system how do you top up the treatment
Thanks very much

Mark

 

[Mottie]

Sounds like you’re converting your system to a sealed one. If you’re asking those sort of questions, perhaps you shouldn’t be doing it yourself.

 

[markyuk]

Why do you assume that ? !!! There are people on here that just want info you know on how things work not to fit stuff that's what plumbers are for !!!
It's all ready sealed just want to understand it. I have only ever had vented systems
It's a system bolier with hot water tank and sealed heating.

 

[Mottie]

Well then, why didn’t you just say something like “This is what I’ve got, is this correct”?

I’m not a plumber but as far as I know, to top up the treatment you’ll have to drain some fluid out to get the treatment in. You can add it wherever is convenient as it will circulate, usually at the highest point as that will mean you only need to drain a little water off. It will then need repressurising. There should be a tap and a flexi hose with a gauge near it. Pressurise it to between 1 - 1.5 bar. I’m sure someone will correct me if I’m wrong.

I wouldn’t think it matters where the pressure vessel is fitted as the whole system will be at the same pressure but there is probably some logistical reason to fit it in a certain place. My one is fitted near to the boiler with a safety valve/drain off near to it.

 

[markyuk]

Ok no probs.
Thanks so at the moment the pressure tank is on the hot feed just before the first rad so assuming that's ok then.
Ok and just after that is some sort of brass vent that sticks up like a cone.

Just asking as just moved in and just want to see if it's right as the bloke had fitted the system him self.

Thanks

 

[Mottie]

This is what I have. My boiler/pressure tank is fitted in my loft. The valve you mention is probably the pressure safety valve that lets pressure off if it gets too high and vents it outside - mine is on the right. I would top my treatment up through that bleed nipple, top right.



The brass cone you mention could be what I think us called a tundish which is a visual indicator that the valve is letting off pressure and should be looked at. I say, could be.

Here’s mine, fitted on the hot water supply.

 

[markyuk]

That's the same as mine.

It's an auto vent I have.
Thanks for help

 

[Nige F]

If you have a ladder towel rail with vent+plug @ the top - that's a good place to pour in inhibitor. Turn off both the valves and let out pressure /water @ the union on a valve- after the valve+ before rad- bit messy but you'll catch a lot in a tub and a towel. ( and a bit of water on the bathroom floor won't hurt) Take out plug @ the top, dip the tube with a stick to judge how far down the water is - tighten the union you're draining out of - pour in inhibitor.

 

[Mottie]

That’s a good idea! I have a tall one of them and I’ve just looked and there’s a vent and plug on mine. Will definitely use that method next time I need to add some inhibitor. Thanks.

 

[oldbuffer]

1. The expansion vessel can go anywhere on the system, but mustn't have any valves between it and the boiler, so therefore needs to be before any motorised valves, and in theory before the pump as these always have isolation valves.
2. They are most often fitted to the return pipe, as the water temperature is lower, which is kinder on the rubber diaphragm inside the vessel.
3. The knurled screw fitting top right in photograph is a manual air valve, and not for topping up the inhibitor.
4. Nige F's suggestion for topping up is good. If you want to avoid loosening the valves, shut off both valves (noting how many 1/8 turns on the lockshield), bleed the radiator until no more water comes out, remove the vent, syphon out as much water as you are adding inhibitor (plus 1/2 litre just in case), add inhibitor, replace vent, open valves and bleed.

 

[markyuk]

Thanks very much everyone. I understand it now just new to this type of system and just wanted to know what it done

Mark

 

[Dan Robinson]

The expansion vessel can go anywhere on the system, but mustn't have any valves between it and the boiler, so therefore needs to be before any motorised valves, and in theory before the pump as these always have isolation valves

Wrong I'm afraid.

They are most often fitted to the return pipe, as the water temperature is lower, which is kinder on the rubber diaphragm inside the vessel

That is one reason.

 

[markyuk]

So where do you say Dan ?
Mark

 

[Dan Robinson]

Vessel needs to be on the system neutral point, normally just before the suction side of the pump. Valves have nothing to do with the vessel. It's the safety release/Pressure release valve that's key and must not be valved between the boiler and the valve.

Return temperature is one reason for the vessel being located there, neutral point being the most important.


What worries me about these threads is the horrifying use of the wrong names for things. Especially when DIY'ers reply to one misuse of terminology with another.

 

[markyuk]

Thanks Dan.
I would hoped that people that reply are professional but sound that's not the case then Dan.
I'm trying to understand this so you say the neutral point and before the suction. But where is that. Sorry .
Also the pressure relief valve is on top of my tank is that in the wrong place
Just wanting more info before I call someone to sort it all out.