Connecting combi boiler to thermal store

[Tuna]

So, we have a lpg combi boiler, which I'm planning to connect to our new house's heating system - a small thermal store.

The store has coils for solar, dhw and the boiler, as well as direct connections for UFH and a wood stove.

The boiler does hot water and central heating, though in its previous life (18 months in our caravan whilst we built the house) it just supplied hot water.

So my plan has always been to connect the combi's central heating circuit to the boiler coil on the store. Our solar controller (a Navitron TDC3) has a spare switched output for calling for more heat if the store gets low, so I was planning to combine that with a timer unit (with some magic electrical thingy?) so that the combi comes on when (a) the thermal store is low and (b) it's a sensible time of day.

However, talking to plumbers, they've asked about diverter valves, pumps and all sorts. My expectation was to just do a pipe run between the store and the combi, and that the combi would handle everything - no need for diverter valves, expansion cylinders or other plumbing gubbins - literally just flow and return pipes.

Does that make sense?

Here's a diagram of the internals of the combi boiler (a Glow-Worm Ultracom 24cxi) - looks to me like it has all it needs.


Here's some rubbish ascii art:

 +---------+
 |         |
 | Boiler  |       +-------+
 |         |       |       |
 |         |       |       |
 +---------+       | Store |
 CH |   |CH        |       |
Flow|   |Return    |       |
    |   +----------+       |
    |      Coil out|       |
    |              |       |
    +--------------+       |
           Coil in |       |
                   |       |
===================================

Edited by Tuna on Thursday 9th December 14:53

[Tuna]

ferg said:

You should keep some hot supply from the boiler to a tap rather then ignore it,

So plumb in a cold feed and put a tap on the wall for hot?

[Tuna]

ferg said:

PS Don't talk to those plumbers again...

We've fired our plumbers as they made lots of promising noises, then ballsed up the job. The basics are in place, but we're currently running off an immersion element as there's no way on earth I'd let them back in to connect the other heat sources up.

So now we're trying to find a reliable plumber that won't run a mile the moment we mention stuff like solar and thermal stores. Not surprisingly most are coming in to see a half finished job and are sucking their teeth and asking "what's going on here then?".

[Tuna]

BTW - Thanks Ferg, I appreciate you answer a lot of the questions around here.

We'd have you round like a shot but (a) you're not that close to Cambridge and (b) I'm sure you've got work right through to next spring right now.