"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...SES%20850%20OT
%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.
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.
The reference to OpenTherm has nothing to do with the Honeywell
Chronotherm, but to the OpenTherm protocol used for data
communication between the boiler and the controller. See:
http://www.opentherm.org/
I said, "Opentherm standard", which is a "open" standard used by
those who sign up to it, as the opentherm link you gave explains.
Currently is only a protocol between boiler and room temperature
sensor. Two microprocessor based devices connected via a common
"open" protocol so all makers equipment using the protocol can
talk to each other. The boiler and an intelligent room temp
sensor (this may have a sophisticated clock in it as in a clock
stat, like the Chronotherm). There was talk of it 5 years ago,
but only recently have a number of makers started to incorporate
it into their pcbs (Maxie will have to get to know it as he fixes
pcb's).
A number of boiler makers use it, mainly German and Dutch, I
believe an Ideal boiler can use the Opentherm protocol.
Honeywell, Danfoss, Siemens, Landis, etc make room temperature
sensors which will connect onto these boilers and modulate the
burner or switch the boiler off/on, optimise the start stop of the
boiler, etc (the Honeywell Chronotherm optimises switching on).
Then no rip-off proprietary room sensors to buy, as any makers
sensor will do.
I am sure a Chronotherm using the Opentherm protocol can be bought
for under £133 if you look around...
The fact that Keston calls it a Chronotherm does not imply that it is
a Honeywell device. The manual that you linked to on the Keston site
is indeed for a Honeywell product (the CX51), but the PDF is dated
2002 and there is no reference to it that I can find on the Honeywell
UK site. Perhaps it's out there somewhere, but the Keston-badged
device that I have is certainly a Theben product.
As you say, OT devices are uncommon - I couldn't readily find a cheap
one, and opted for the Keston-badged device.
Few people in the heating industry have heard of "Opentherm", so
many opentherm compatible boilers will not be used to their
maximum efficiency and I see this boiler being one of them. If
pushed properly, even dumb plumbers could even understand it, it
is that simple, with all the control done on the pcb, not in crude
electrical devices external to the boiler, as is now. The contol
is thought out for them, all they have to do is connect up the
devices with wires directly back to the boiler using two core
wires which don't care what way around the wires go in the
terminals.
I have the Keston C36. I confess that I was hoping for more from the
OT controller, but perhaps I was over optimistic. Given that OT is a
two-way protocol, it offers:
- display of boiler and pump info, including burner and pump status,
flow temp etc
- display of outside temp
- reasonably comprehensive time programming
- optimised temp control (rather than directly programmed room temp)
via the external temp sensor and return flow temp [but this is poorly
explained in the manual]
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...
I'm pleased with the running costs - my gas bill is currently running
at £30 per month for a 12-rad system.
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.
-- Oxford University Press, Edpress News