"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/downloads/BA_RAMSES%20850%20OT%20neutral_2007_01_309%20872_G B.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. The temperature sensing device can
have far much more funtionality and sets the boiler temperature from 0C to
82C, as you found out.

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.

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 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.

The Chronotherm modulation controller is sold openly on the Continent for
less than £133. The Opentherm protocol was a Dutch/German initiative. I
heard the Atmos Multi is supposed to use OpenTherm to its controller, but it
does not state in the manual that it is. I assume if you sign up to
OpenTherm you make it clear it is OpenTherm.

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]

How is the DHW flowrate from the C36?

The problem with current OpenTherm controllers is that they are too complex
for the average user. Simple to use, connect and fire up devices should be
made, then the nerd aspect of the OpenTherm protocol will disappear and the
dumb plumber will use them as the electronic control settings can be
pre-set.

Some Danfoss, and others, OpenTherm room sensors look like normal room stats
with normal knobs. And yes using these when you turn up the knob the burner
will modulate up as most people think happens with normal on-off room stat.
The time clock aspect is usually done via a switched live at the pcb and
separate clock usually on the boiler.. Yet how many of these boiler will
have normal crap on-off stat fitted instead of an OpenTherm room sensor
(looks like a stat), because of ignorance and the OpenTherm device will be
more expensive - yet it delivers full burner modulation of boiler giving
superior economy and comfort conditions.

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?