Bodgit coughed up some electrons that declared:

I installed a Pandora heatbank from DPC about 2 years ago. It's always
worked well but I've always been concerned that it seems to leak a lot
of heat, but I've never got round to actually measuring it until now
(had 2 kids in the meantime that took all my time!)

The design code is CPC-150-ABBDA-AAJA-H (150 litre Pandora)
At 10.30pm the temp was 78 deg.C.
At 8.00 am the temp was 64 deg.C.

It was completely powered down overnight, so the loss can not be due
to a dripping tap etc.

I work that out as 8.8KJ over 9.5 hours, so an average heat loss of
about 250W, which seems very high!

I'm wondering if such a high loss could be due to the fittings etc. or
if it's likely that the insulation is compromised.

I emailed DPC a week ago but haven't received a reply as yet.

Any advice gratefully received!

Thanks,
Dave.

How thick is the tank insulation? 25 or 50mm?

Do you have pipe lagging on everything, including the expansion pipe (if
this isn't an integral unit).

250W doesn't seem too massive (think how warm an airing cupboard is with a
regular tank in) but it might be possible to improve it in situ.

You can get some polystyrene or 25mm celotex (Wicks and B&Q sometimes sell
cut off small panels) and using toothpicks or tape, make little boxes to
contain the plate heat exchanger and pumps (pumps: do NOT enclose the motor
body or control, just make a little half box to go round the back and up
the sides of the impeller section only).

Some of that will probably make a gnat's breath of difference but the
cumulative savings might knock 50-100W off your leakage.

If you made a U-value assumption for the foam around the tank, it would be
possible to take a wild guesstimate calculation for the expected leakage
based on surface area and inner and outer face temps.

Also, there's usually naff all insulation under the tank (insulation won't
take the wieght) - is it bleeding heat through the floor?

Nothing to stop you adding a tank jacket (big one) to the outside, as long
as you don't cover up the electrical bits.

Overall, as your leakage happened overnight, I suspect your 250W is mostly
going out the tank wall and immediately adjacent pipes, but that's doesn't
invalidate insulating the other bits as they'll bleed when it's in use).

Just some thoughts, not a definitative answer...

Tim