Sealed indirect heating system pressure problem

Hello!

I've just moved into a 2012 built house in Bristol, England.

It has a sealed heating/water system that (1) I don't fully understand the logic of, and (2) I'm pretty sure has a problem.

Overview: 4 bedroom house, 2 bathrooms (1 with bath, 1 with shower) 3 toilets 5 sinks (1 kitchen, 1 utility room, 1 WC, 2 bathroom) 13 radiators of varying sizes

In the utility room, there is a Glowworm Flexicom 15hx boiler In a closet is a Range Tribune Indirect immersion tank. The guts of the tank.

Now, as far as I understand it, mine is an indirect system, where the boiler heats the water which feeds through a coil inside the tank which heats the seperate tank water which is then pumped through the radiators as required. There is also a seperate immersion heating element that can heat the tank water if the boiler fails.

What I don't understand is how the hot (and cold) water to the taps is connected. Is that purely from the boiler? Or can the immersion heater supply hot water to taps?

Both hot and cold water taps (and the shower) have water pressure that I think is lower than a pressurised system should supply. Our previous house had only a combi boiler and the tap/shower pressure was much higher (though was a smaller house).

I've not been able to get a clear understanding of how my system works, so any advice would be very welcome.

As far as the (2) problem, the pressure gauge off of the expansion tank read 0 when we moved in. For some reason, the filling loop was left connected (which I've read is illegal), so I opened both taps up, and pressurised the system up to the red mark, at about 1.3bar. Whilst it did this, there was a very slow drip from the filler loop.

The following morning, it was back down around 0.2 bar. Where is that pressure going?

Also, why are there two expansion tanks? Should I test the air bladder pressure in them? Might a problem there cause my low pressure problem?

Thanks for reading this wall of text, and many thanks in advance for any help or advice I am offered!

submitted by /u/Rogerwilco1974
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