"Doctor Drivel" wrote in
reenews.net:
"Richard Perkin" wrote in message
...
"Doctor Drivel" wrote in
reenews.net:
"Richard Perkin" wrote in message
...
"Doctor Drivel" wrote in
reenews.net:
... The DHW cylinder sensor (not
sure of price) and the Opentherm standard room temp
controller/programmer/optimiser fitted (Keston use the
Honeywell Chronotherm, which can be bought a lot cheaper
elsewhere rather than the £133 Keston ask for it)...
Err... The programmer badged by
Keston is the Theben Ramses 850 OT.
See:
http://www.theben-ag.com/fileadmin/d...AMSES%20850%20
OT%20neutral_2007_01_309%20872_GB.pdf
Here is the Chrontherm on the Keston site:
http://www.keston.co.uk/downloads/userguides/CX51-u.pdf
In the manuals they specifically state Chronotherm
Indeed. The description and part number a
Keston Chronotherm Room Controller C.17.4.21.00.0
The device supplied to me approx 18 months ago under this
description and part number is the Theben Ramses 850 OT and its
details can be found at the link I gave.
It appears, Keston are using the Honeywell Chronotherm for the
current unit.
The name confused me when I was speccing the system, and I spoke
to the Keston Technical Department who confirmed that it was not
a Honeywell product. Unsurprisingly, they did not offer any more
info on where I could get a lower cost alternative but did
confirm that any OpenTherm (OT) device would do.
"Any" OpenTherm device will do, that is the beauty of the OT
protocol, you may not have realised that at the time.
Of course I realised it - that's one of the reasons why I spoke to
Keston. I (like you) also realised that the asking price for the
'Keston' controller was high - but the company couldn't/wouldn't
suggest an alternative, and I struggled to find one. Perhaps you know
of others readily available in the UK? Or (for the rcord) where the
Honeywell OT device can be purchased?
You will find the name "Chrontherm is heavily trademarked and
legally protected. The Keston link is to the Honeywell product.
It will be the Honeywell.
The same name and part numer are in the C36 manual. The same product
info was also on the Keston site 18 months ago. When I ordered the
controller, what was delivered was the Theben device *not* a
Honeywell.
Perhaps things have changed - you could try ringing them up...
How is the DHW flowrate from the C36?
It's best described as 'adequate'. I was hoping for better - indeed,
a major reason for selecting the C36 was its high output (CH output
OTT for my house, although of course it's fully modulating so no
problem there) and consequent high DHW flow rate. The spec is: 14.5
l/min @ 35deg C rise, 17 l/min @ 30 deg C rise.
However, despite this it is still slower than I would like to fill a
bath with 'properly hot' water. However, the flow rate for a drencher
shower is truly excellent, as you would expect.
The bolier is sited some distance from the bathroom, and the length
of pipework has a significant impact as there is a considerable
'slug' of cold water to come from the tap before the hot water flows
well.
But these are well known consequences of using a combi, so I'm not
surprised.
However, whether this is much better than an external temp sensor
+ normal switched live controller I'm not sure, since with just
the external temp sensor the boiler implements weather
compensation directly...
It will be, as the room temperature is supposed to influence the
burner too. First stage is outside weather temperature then the
room temp influence to control the burner - cascade.
I'm pleased with the running costs - my gas bill is currently
running at £30 per month for a 12-rad system.
Appears the electronic controls are doing their job. Does it
maintain a constant room temperature?
No, it doesn't quite work like that. The Theben controller has two
modes of operation: you can set a target room temperature, or (if the
external temp sensor is present) use weather compensated control.
Weather compensated control is the default when the sensor is fitted,
or more accurately, since the snsor is connected to the boiler
system, when the boiler tells the controller via OT that it is
present. When it is used, the controller uses a predefined heating
curve, but it is possible to set the start and end points. This is
very poorly explained in the manual (read it at the link above) and I
am using the default settings.
This seems to work OK. All rads but the usual suspects (hall,
bathroom) are fitted with TRVs and the controller is in the hall. If
it were set for a fixed target temp I would use 21 deg C - in
practice it works automagically with a displayed temp of around 21 -
22 deg. Room temp is controlled by the TRVs, but the controller +
weather compensation ensure that the CH flow rarely rises above 65
deg (although the max would be 82 deg).
As I write this the controller says the (hall) room temp is 22.6 deg
and the flow temp is 43 deg against an outside temp of 8 deg.
The house is always comfortably warm. In fact many visitors find it
hot, but having spent a very cold Derbyshire childhood I vowed never
to be cold again, so we like it like that
Quite how the device implements the control I'm unclear (which is
unlike me - I like to know the nitty gritty) and I'd prefer to
'play', but the default setting works well and the running costs are
low.
Kind regards
--
Richard Perkin
To email me, change the AT in the address below
richard.perkinATmyrealbox.com
It's is not, it isn't ain't, and it's it's, not its, if you mean it
is. If you don't, it's its. Then too, it's hers. It isn't her's.
It isn't our's either. It's ours, and likewise yours and theirs.
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