what is this?

[doitall]

I don't think so croydoncorgy,

The pipe from the air seperator on the left No1, is the cold feed, which is obviously blocked or water from the tank would be flooding out, the second pipe No2 is the expansion,

3 & 8 are returns.
7 is the common return to the boiler.
9 is the cylinder flow.
4 is the heating flow.
5 is the flow from the boiler.

The system is in serious need of a qualified tradesman, not least for the reasons youmentioned already.

how is the cylinder fed from the same tank or mains supply.

 

[bobonacus]

you are correct, no1 is the feed for the system and 3 is the return from the rads, that compeletly slipped my mind even when I was trying to draw the system diagram

I couldn't believe 1 was the feed for the boiler as it IS coming from the main cold water tank but I removed the air seperator and cleaned it out and all kinds of crap came out (unsurprisingly)

After refitting it still wasn't pressurizing properly so I have filled the system from attaching a hose pipe to no 1. Before you start saying this is awful, I know it's awful but the system was NOT fitted by me, I bought the house a few years ago and this is the first time any work has been needed on the system. I need the heating working tonight as it bloody cold!!! and as it's been like this for who knows how many years another week isn't going to hurt!!

As far as I now understand what I need to do is just run no1 and no2 up into a seperate header tank in the loft and the system will be a lot better. I obviously need to flush the main cold water tank through with god know what to clean it .... or replace it may well be an idea!

What size header tank do I need for the boiler?

I do appreciate your help but just because the heating in my house has been fitted by an idiot doesn't mean I am one and can't fix the propblem and have to call an engineer ... thats the point of this diy forum isn't it?

cheers
Robert

 

[doitall]

The idea of this forum is to try an identify problems such as yours, then advice the best way forward.

Telling someone without the full information is/can be very dangerous for the questionair and his family.

Yours is a typical example, where from your original question a whole can of worms were opened.

and on that subject, your best advice is to convert to a sealed system and forget the tank, the pump is not ideally situated and will cause problems with air etc, etc.

 

[croydoncorgi]

Yup - quickest way out of the chaos is probably to convert to a sealed system...
BUT

1. Make ABSOLUTELY SURE that your boiler has an overheat thermostat and is correctly configured to operate on a sealed system. I believe the Prima B is capable of being used in this way but check carefully before proceeding.

2. Check you have no obvious / known leaks on your system

3. Make sure the sealed system components are fitted EXACTLY as specified and that the overflow is run correctly to outside the building. (Only last week I came across a potential bomb where a sealed system had not been correctly installed.)

4 Sort out the auto bleed valves (ABVs). I assume from your pix that the boiler is at the same level (roughly) as the pump, 3-port valve, etc. If so, at least the ABV on the Flow side of the boiler will be in the 'suction zone' of the pump (Look up 'neutral point' of central heating systems if you don't follow my drift). Probably best to remove ABVs from above boiler and replace with finger vents for use when filling the system. Remove the air extractor and re-do the plumbing around the pump so that there's a 'high point' with an ABV between pump and 3-port. That way, the system will continue to stay airtight even if pressurisation is partly lost. If you just remove the air-extractor and replace it in the same position with an ABV, it will draw IN air if pressure drops. Ideally, in a presssurised system the pressure will always stay up, but it's still best to prevent the thing from gulping air if it drops.