System boiler system - how does the system top up after loss of water?

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mjgreen81

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Hi all,

Apologies in advance if I get any terminology incorrect.

I moved into a house about a year ago with a system boiler. I've always lived in houses with a regular/conventional boiler system so I'm still getting my head around how a system boiler works.

I'm looking at doing some decorating soon and plan to remove some radiators so I can paint behind them. With a regular boiler system this is no problem, I remove the radiator,top the system back up with water until the pressure is ok and then bled.

However, it dawned on me that my system boiler has no pressure meter anywhere so I am not sure what I need to do to ensure everything is ok after I remove the radiator.

Any advice or useful diagrams to help me understand would be appreciated.


Thanks in advance
 
If it is a sealed system, you must have a pressure gauge somewhere. Usually it’s on the boiler itself. You top it up via a flexible braided hose, again, usually on or near the boiler itself. What boiler is it?
 
Do you have a small tank in the loft ,known as a feed and expansion cistern . If so ,that's what feeds the system.
 
With a system using a header tank often radiators need bleeding twice one with only feed open and once with only return. And with any boiler inhibitor needs replacing if you drain any coolant off. And of course check the header tank is refilling OK.
 
I've attached a couple of images that show my boiler and cylinder.

The boiler is an Ideal Classic.

There is no tank in the loft (the loft has been converted)

IMG_20230801_135138.jpg



IMG_20230801_135258.jpg
 
How can it be a system boiler with two external pumps? I thought a system boiler had everything inside the casing?
 
I'm not sure, but when I first moved into the house I posted on diynot for some advice and several people confirmed it was a system boiler.
 
Your system is fairly complicated ,in a nutshell it allows mains cold water to be heated via the cylinders heat store to provide domestic hot water to your taps. The water inside the cylinder doesn't mix with the hot water that comes out your taps. As opposed to a basic copper cylinder that holds the domestic hot water that does come out your taps
 
Thank you for explaining it so clearly.

So is the water that is held in the cylinder pumped around the radiators? If yes, what happens when I remove a radiator (and therefore lose some water?)
 
Just to confirm a few things.
1. Turning off your main cold water stopcock does stop water from coming out your hot taps doesn't it ?
2. If I am correct you wouldn't have domestic hot water( DHW) unless you use programmer to heat water in the cylinder first.
3. The small tank above the cylinder should have a removable lid ,inside a ball cock ( with a float ) .Does it ?
..............
There are a number of different types / set ups and I am not over familiar with them all to be frank ,but I am pretty certain that the small cistern ( tank above cylinder) only supplies the boiler / cylinder and rads.
Answering the above questions will confirm.
 
at the top of your HW cylinder you will see a silver braided hose, where this joins to the copper pipe there is a ballofix valve it is closed, slot across the direction of flow, you need to use a screwdriver to turn the slot upwards and the small header tank will fill
 
Sorry for the delay in getting back.

Discovered my stopcock was seized today while testing turning the water off and it took a bit of wrestling to unsieze it. Glad I found out now rather than when I really needed to turn it off!

To answer you questions...

1.) Correct, HW stops coming out of the tap when the mains is switched off.

2.) Correct. As a side-note, the programmer doesn't let me have CH alone, you have to have the HW turned on as well.

3.) Correct. It's empty at the moment. Not sure if it should be? (I haven't had any problems using the CH although obviously it's been a few months since it's been on).
 
ianmcd said:
at the top of your HW cylinder you will see a silver braided hose, where this joins to the copper pipe there is a ballofix valve it is closed, slot across the direction of flow, you need to use a screwdriver to turn the slot upwards and the small header tank will fill
Click to expand...

Can you explain the reason for doing this? It's currently empty (not sure if it should be) but I don't really understand the function of it. I had no problems with heating since I moved in a year ago and haven't touched that valve.

Thanks
 
It should have water in the cistern ,doesn't need to be full, 3 or 4 inches deep when system is cold, can be higher. It's a feed and expansion cistern and keeps the system topped up.
 
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