Indentifying system type, sealed, gravity, vented. Checking pressure. Smart upgrade.

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I am looking to make my heating system smart (e.g. Drayton Wiser) and also looking to check the pressure. I would normally ask the installer (a long acquaintance of the family) - but unfortunately he has since passed away.

The system (old family place in Ireland) was updated in 2015 with an Ideal Logic System boiler 18IE. This boiler has 3 main pipes underneath. Gas, CH flow (hot water out) and CH return. The flow valve has a pressure gauge on it. There is also a plastic pipe for condensate and a copper pipe to the outside (for pressure release). The boiler contains an expansion vessel.
The installation manual states on page 6 "Introduction" - "The boiler is suitable for connection to fully pumped sealed heating systems ONLY" (capitals from the manual).

That seems fairly clear even to an absolute non plumbing expert like me ;)

So, I assume that the hot water heated directly by the boiler is in a sealed loop. This water goes to the radiators and/or to the vented tank in the airing cupboard to indirectly heat the water there.
I assume this water is/must be under some pressure - shown on the gauge. It must be possible to add/top up water from the mains to this water "loop" to maintain pressure - e.g. after bleeding radiators or as I plan - adding trv valve etc. Please correct me if I am wrong.

So I set about looking for a place where filling might be possible. I assumed I was looking for a place (possibly in and around the airing cupboard) where a temporary flex connection from the mains to the otherwise sealed CH loop was offered in some way. The boiler itself has no filling loop - it is not connected directly to the mains in any way (AFAIK).

So the airing cupboard presents probably a standard picture. A copper pipe from the attic water tank connects to the bottom of the cylinder. Hot water for hot water taps comes from a copper pipe at the top of the cylinder. To heat the cylinder a CH flow pipe from the boiler enters the cylinder in the bottom 1/4 and emerges (CH return) from the cylinder in the top 1/4 and goes back to the boiler. On "top" of this return circuit there is a Valmat 10bar automatic air vent.

So far - I get it.

But the next bit is "strange" (see attached picture). About 1/3 down the CH-return pipe from the cylinder in the airing cupboard this pipe is joined ("T" piece) by a horizontal pipe taken from the same pipe that fills the cylinder for the hot water to be heated. i.e. the downward pipe from the water tank in the attic(!)
This connecting pipe has a red "stop cock lever" which appears to be open. And just before the connection to the CH-return pipe it has a check valve. This valve ensures water can only go from the attic water tank into the CH-return pipe.

This has me a little bit confused. Has anyone else seen something like this.
Does it mean the system is pressurised from the attic or is just some kind of "automatic" pressure back-up system to prevent complete pressure loss and I still have to pressurise the system (loop water from the boiler) somehow elsewhere.

"Make-up water" - the manual talks about this on page 11. "Provision must be made for replacing water loss from the system"
It talks about:
  1. a "manual" make-up vessel... non-return valve
  2. where a make-up vessel is difficult by "pre-pressurising" the system.

My questions:
Is the arrangement I have (with the pipe from the attic connected by a one way valve) in fact this "make up vessel". i.e. I do not need to do any kind of pressurising/re-pressurising after bleeding rads. etc. (i.e. I can "ignore" the pressure gauge!)

Drayton Wiser says its system does not work with gravity fed systems. I assume my system is not gravity fed in the way they mean - but conventional.

Thanks for any insights to my system :)
CH-return.cylinder.jpg
 

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I'm not sure about the pressurisation bit so I'll leave that to others. Drayton Wiser (like any other control system) will struggle if your hot water cylinder is heated by gravity circulation only (usual signs- large supply pipes from boiler to cylinder, min 22mm, more likely 28mm or larger, existing controller doesn't allow central heating without hot water also being heated).
So. Do you have motorised valves on this setup anywhere?
 
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There is currently just a single motorised valve on the system. So the option is HW and CH (valve open) or just HW (valve closed). See picture. The picture is from directly underneath the boiler. Top l.h.s. pipe is CH flow.

For background, the current programmer is a mechanical timer, immermat Flash Programmer 1 (model 31005). Basically just timed on/off. The motorised valve has its own switch. Basically HW and CH (winter) and HW only (summer)
 

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Does the pump run when hot water is being heated? Either way you can use the Wiser kit, it's not ideal from a control point of view having the cylinder heated all the time but as long as it is well insulated, once it reaches the temperature of the boiler primary it won't get any hotter & will stop absorbing energy.
If you do get the Wiser stuff you only need the 2 channel hub - 1 for heating, 1 for hot water. You can also fit the WiFi TRVs to give you finer control if you want but be wary, there is probably a radiator on the system that gets hot when hot water only is selected- if so then don't fit TRVs to it, it's acting as a bypass/heatsink for the boiler
 
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