Help understanding plumbing system

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I've moved house and I'm trying to understand what's going on with the plumbing.

I have a combi boiler and then the below system for central heating and under floor heating. However this cylinder is turned off electrically but is hot, so is this fed from the combi? Is this tank just storage for hot water taps? I'm confused

The pipes going through the floor are labelled:

HTG (Heating - as in radiators?)
UFH (Under Floor Heating, presumably)
BF - Boiler Feed? But this is connected to Flow on the tank and the HTG and UFH pipes...
MCW - Mains Cold Water?
BC - Boiler Cold?
R - (Return? from the radiators and UFH presumably)

Can you guys help me understand what these abbreviations mean and if my thinking is right? I'm sure its obvious to someone with more plumbing knowledge than I.

See attached pics

Thanks
PXL_20220125_173046947.jpg PXL_20220125_173022364.PANO.jpg
 
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What makes you think you have a combi- pic would help.
You may have a combi boiler but you also have an unvented hot water cylinder which can be heated either by the gas boiler (preferred option, it's a lot cheaper unless you have PV solar panels) or the immersion heaters (expensive unless PV).
If the house is largeish you may find that the combi supplies dhw to the kitchen sink only, the cylinder looks after the bathrooms. Experiment- with the heating off, turn on a hot tap, see if the boiler fires instantly and shuts down as soon as you turn that hot tap off. Repeat for all hot taps, showers etc.
Is this a brand new house or heating system? If yes, get the contractors back in to put a cover on that pattress box below the controller- there will be 240v on some of those cables. (If no, go to Screwfix or toolstation or wherever and buy and fit a cover).
Your guesses on the abbreviations sound feasible...
 
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@oldbutnotdead thanks for the reply.

Combi pic attached.

I'll do the tap-test as you describe, good iea.

Re pattress, I've taken that lid off - I'm trying to determine which thermostat is controlling what as it's currently a confusing mystery that doesn't work as I'd expect.
 

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You don't have a combi boiler. Your boiler heats the water that's stored in the cylinder,but you must set the programmer to do that. As said above ,electric immersion heaters can also be used .
 
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Boiler pic confirms it- not a combi, not enough pipes. The 22mm pipe that reduces to 15 is the gas supply. The 15mm is cold water main (only needed to pressurise the system). The other 2 x 22mm pipes are primary heat flow and return.
Control wise you should somewhere have a manifold for the under floor heating (it'll be at or near floor level, look for a lot of fairly small pipes.
At the moment there are 2 visible 2 port motorised valves- one controlling heat to the cylinder, the other controlling heat to the heating (radiators). These are probably controlled by that programmer in the pic. When you find the ufh manifold there should be another motorised valve there, very likely controlled by a stand-alone programmer cum thermostat in one of the ground floor rooms.
 
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@terryplumb @oldbutnotdead Thanks for the insight and help.

The programmer on the wall controls the topmost valve, which goes to FLOW on the tank.

I've now found the radiator thermostat control, this is the lower valve (pipe labelled HTG)

The UFH manifold is behind a cupboard full of stuff, shall investigate tomorrow but I'm sure youre right, it will have its own valves (multiple rooms)

@ianmcd What makes you say that? (You won't offend me, not my handywork!)
 
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installer has only lagged tiny bits, and very poorly at that, and as for that expanding foam fiasco, less said about that the better
 
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