Anyone know of a supplier of fast recovery vented hot water cylinders of
Loads of unvented cylinder are available at about that size, but your
common or garden type seems scarce...
The background (this is partly an exercise in thinking aloud!):
Just deciding if it is cost effective to make a heat bank...
The choices for main pressure HW production seems to come down to:
COTS Heatbank like DPS Pandora
I got a quote from them, and a 250L one with all the trimmings, ready to
install and go, with pump and 160kW PHE on the output, a 12kW indirect
coil to heat, plus 28mm blending valve, 3kW immersion, scale
reduction, looks like costing about £1900
The paraphernalia around the edges could come to say £450, so much
depends on the cost of a suitable tank...
anything from £500 - £900
(and no, I don't want a combi, so let's not go there!)
Now most of the killer applications of a heat bank don't really apply in
my case. I won't be integrating solar, solid fuel, or biomass etc,
and heat pumps are at best only likely to match mains gas for price. So
the main attraction is that in a hard water area, any scaling is going
to be limited to the PHE, its a low maintenance option, and the
(minimal) risks from having a pressurised cylinder are avoided.
Installation is slightly easier, since there is no need for a emergency
 Yes I know it supposed to be installed by a G3 certified bod, but
they all come under building regs these days, and how many people
remember to do a BN for a hot water tank swap? If one were to DIY, this
is quite a cheap option. Pay for someone to do it however would probably
make it the most expensive.
 DPS seemed keen on fitting a HydroFlow HS38A electronic water
conditioning widget... I enquired if they found this effective, and they
seemed to think that it worked in this application.
 The ideal roof slope is littered with dormers and chimneys, so
nowhere to put a decent sized panel. (plus I am trying to do this with
minimum capital outlay!)
 Doing the sums and planning for future requirements (i.e. at some
point will have two teenagers co-resident <shudder>), I reckon on
needing 400L of final temperature water from one "charge" of the
store. That comes to about 230L of store temp (70 deg C) water required
to achieve that (spreadsheet available if you want it).
 Best overall efficiency is going to be achieved with a weather
compensating controller on the boiler. The modern integrated electronic
jobbies also seem to take care of all sorts of little details like being
able to programme a period of high flow temperature operation for water
cylinder recharging, while running the rad zones at far more efficent
and appropriate temperatures. This tends to suggest that the best mode
of operation, is to recharge the store during a heating setback period,
and not attempt to do it while running any heating zones. The logic for
this being you don't interrupt your heating, and your rad flow temp
won't have to run up to 70 all the time the HW is calling for heat.
The down side of this is that you can't really augment the size of the
store by allowing for concurrent boiler recharging - hence it needs to
be big enough to cope with most eventualities.
Click to see the full signature.