Hi All,

An easy question for you knowledgeable people!!

We have a elderly but functional combi boiler (in the kitchen) with a
mechanical thermostat in the hallway.

The problem I have is that the range from where the thermostat
switches on the heating to where it switches off the boiler is
enormous. For example, we either freeze or we get roasted! Keeping a
steady temperature in the house is near impossible.

I appreciate that the range of the thermostat shouldn’t be too narrow.

At the moment the thermostat is used as more of an on off switch.

First Question: Is it possible that the mechanical thermostat is
faulty?

Second question: Would replacing this thermostat with a wireless
digital thermostat improve the situation? There is of course the added
advantage of being able to move the thermostat around the house at our
convenience.

Third question: Can it be done? Is it easily DIY able. I’m fairly
adept at these sorts of things but this is not an area I’ve looked at
before.

Boiler: Ferroli Modena 102
Thermostat: SunVic TLX

Thanks.

beamer wrote :

Third question: Can it be done? Is it easily DIY able. Im fairly
adept at these sorts of things but this is not an area Ive looked at
before.

Boiler: Ferroli Modena 102
Thermostat: SunVic TLX

Thanks.

I don't know about the specifics, so generalisations...

There will not be much difference between the mechanical wired stat and
a wireless one, unless the wired one is faulty or incorrectly wired.
One mistake often made with the wired ones, which might be the cause of
your problem was to omit the neutral connection. Basically when the
stat turned on, it also powered a small heater within the stat, which
helped to prevent overshoot - it warmed up the by-metal strip causing
it to click open a little earlier than it would otherwise do, thus
reducing the hysteresis. This being the difference in two temperatures,
between it switching on and switching back off.

The modern wireless types respond faster and the essential hysteresis
is programmed into them.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

On Thu, 13 Nov 2008 12:16:37 -0800 (PST), beamer
wrote:

Hi All,

An easy question for you knowledgeable people!!

We have a elderly but functional combi boiler (in the kitchen) with a
mechanical thermostat in the hallway.

The problem I have is that the range from where the thermostat
switches on the heating to where it switches off the boiler is
enormous. For example, we either freeze or we get roasted! Keeping a
steady temperature in the house is near impossible.

I appreciate that the range of the thermostat shouldn’t be too narrow.

At the moment the thermostat is used as more of an on off switch.

First Question: Is it possible that the mechanical thermostat is
faulty?

Second question: Would replacing this thermostat with a wireless
digital thermostat improve the situation? There is of course the added
advantage of being able to move the thermostat around the house at our
convenience.

Third question: Can it be done? Is it easily DIY able. I’m fairly
adept at these sorts of things but this is not an area I’ve looked at
before.

Boiler: Ferroli Modena 102
Thermostat: SunVic TLX

Thanks.

Either change it or get it changed for a modern programmable equivalent. They
are available for less than £30 on Ebay and will give you far greater control of
temperatures throughout the day. Some can be set to either 0.5 or 1 degree
switching range. Get one with five or six changes for each day of the week,
especially if you want a different pattern at the weekend. The Danfoss TP4000
for example doesn't differentiate between the days of the week.

Most simply use the live and switched live and the neutral and earth can be left
insulated and isolated i.e. in a small terminal block, tucked away at the back.
Obviously make sure the power is removed from the heating system before messing
about with the wiring.

Andy

Andy Cap wrote re. wireless thermostats:

Most simply use the live and switched live and the neutral and earth can
be left insulated and isolated i.e. in a small terminal block, tucked away
at the back.

This isn't the case with all of them. Some, e.g. Honeywell HC60NG (used with
the CM927 wireless programmer) need a permanent line and neutral supply for
the electronics in addition to the thermostat switch circuit. Depending on
the design of your boiler you may or may not be able to use the live side
of the existing thermostat connection for this..

A digital programmer will definitely give you much closer control of the
temperature, our CM927 normally keeps the temperature within +/- 0.5C of
the set point.

Of course the wired base unit doesn't need to be located where the original
thermostat is. If you need extra wiring then it's better sited near the
boiler from which it should be fairly easy to run the requisite cables. But
not too near or you might have problems with the radio signal, ours advised
at least 30cm away from metal objects like the boiler housing - and don't
use a metal back box to mount it on.

--
Mike Clarke

On Thu, 13 Nov 2008 23:01:51 +0000, Mike Clarke wrote:

This isn't the case with all of them. Some, e.g. Honeywell HC60NG (used
with the CM927 wireless programmer) need a permanent line and neutral
supply for the electronics in addition to the thermostat switch circuit.
Depending on the design of your boiler you may or may not be able to use
the live side of the existing thermostat connection for this..

Yes but why would you want to put the receiver/relay unit of a wireless
stat where the old wired stat was? Either fit a CM907 wired progstat
(approx £55) in place of the wired thermostat or fit a wireless CM927 with
the HC60 base unit fitted at the boiler, where live, neutral and switched
live are available.



--
YAPH http://yaph.co.uk

This message has been rot13 encrypted twice for added security

On Thu, 13 Nov 2008 20:46:33 +0000, Andy Cap wrote:

Either change it or get it changed for a modern programmable equivalent.
They are available for less than £30 on Ebay

A Horstmann Centaurstat 7-day progstat is £30 from Screwfix

--
John Stumbles

There's nowt as queer as folk.
Especially other folk.

On 14 Nov, 18:09, John Stumbles wrote:
On Thu, 13 Nov 2008 20:46:33 +0000, Andy Cap wrote:
Either change it or get it changed for a modern programmable equivalent..
They are available for less than £30 on Ebay

A Horstmann Centaurstat 7-day progstat is £30 from Screwfix

--
John Stumbles

There's nowt as queer as folk.
Especially other folk.

Hi All,

As usual - lots of good advice. Thanks to all those who have
contributed!

Following the advice, I'm going to replace it - I'm pretty sure it's
not working as it should.

I've not gone for the wireless option. Mainly on the grounds of cost
but also as we'll just go and lose it like the car keys, phones etc
etc.

Screwfix is out of stock of the Horstmann so I stopped at B&Q (for my
sins). The best they had in stock for the price (I hope) was a Sunvic
TLX6501. It seems to have the same functionality and cost around £30.

Assuming my little son lets me, I'll have a go at fitting it
tomorrow!!

Cheers.

On Nov 14, 9:28*pm, beamer wrote:
On 14 Nov, 18:09, John Stumbles wrote:

On Thu, 13 Nov 2008 20:46:33 +0000, Andy Cap wrote:
Either change it or get it changed for a modern programmable equivalent.

beamer wrote:

We have had one other minor irritating little problem with the boiler
that my brain has been trying extremely hard to ignore! Would anyone
have any suggestions for this one?

Combi boiler (Ferroli Modena 102) *- if the heating is firing. Turn on
hot tap - you get hot water. Turn off hot tap, heating also turns off
- one flashing light on the console. If you then reset the boiler the
heating fires up as per normal.

Does the heating come back on after a few minutes if you just leave it? If
so this might be a design "feature". We have a Worcester 350 combi that
does something similar and in the manual it states:

"The appliance will supply heat to the central heating system as required. A
demand for hot water will override the central heating requirements
.....
When hot water is no longer required the burner will extinguish and a
waiting period of about 3 minutes will prevail before returning to the
central heating state and its normal mode of operation"

But I've no idea why they deem this to be necessary.

--
Mike Clarke

On Mon, 17 Nov 2008 13:27:54 -0800, beamer wrote:

On Nov 14, 9:28Â*pm, beamer wrote:
On 14 Nov, 18:09, John Stumbles wrote:

On Thu, 13 Nov 2008 20:46:33 +0000, Andy Cap wrote:
Either change it or get it changed for a modern programmable
equivalent. They are available for less than £30 on Ebay

A Horstmann Centaurstat 7-day progstat is £30 from Screwfix

--
John Stumbles

There's nowt as queer as folk.
Especially other folk.

Hi All,

As usual - lots of good advice. Thanks to all those who have
contributed!

Following the advice, I'm going to replace it - I'm pretty sure it's
not working as it should.

I've not gone for the wireless option. Mainly on the grounds of cost
but also as we'll just go and lose it like the car keys, phones etc
etc.

Screwfix is out of stock of the Horstmann so I stopped at B&Q (for my
sins). The best they had in stock for the price (I hope) was a Â*Sunvic
TLX6501. It seems to have the same functionality and cost around £30.

Assuming my little son lets me, I'll have a go at fitting it tomorrow!!

Cheers.

Right - ten minutes later and it's fitted., So far seems to be a great
improvement but I think I'll need to carry on testing a little longer to
be sure.

We have had one other minor irritating little problem with the boiler
that my brain has been trying extremely hard to ignore! Would anyone
have any suggestions for this one?

Combi boiler (Ferroli Modena 102) - if the heating is firing. Turn on
hot tap - you get hot water. Turn off hot tap, heating also turns off -
one flashing light on the console. If you then reset the boiler the
heating fires up as per normal.

After DHW mode the boiler stops firing. Very likely the boiler then
considers this to be the same as if the boiler had stopped firing due to
it's internal thermostat (indeed the primary water may well be at or above
the CH thermostat point). The boiler is then likely to wait for a set
minimum time (usually a few minutes) before firing again. This is how
quite a few boilers seem to work. I dunno if the Moderna 102 is like that.
The delay is to implement an anti-short-cycle feature.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html

In an earlier contribution to this discussion,
beamer wrote:

Hi All,

An easy question for you knowledgeable people!!

We have a elderly but functional combi boiler (in the kitchen) with a
mechanical thermostat in the hallway.

The problem I have is that the range from where the thermostat
switches on the heating to where it switches off the boiler is
enormous. For example, we either freeze or we get roasted! Keeping a
steady temperature in the house is near impossible.

I appreciate that the range of the thermostat shouldn’t be too narrow.

At the moment the thermostat is used as more of an on off switch.

First Question: Is it possible that the mechanical thermostat is
faulty?

Yes, it sounds as if your stat has excessive hysteresis - assuming that it's
working at all. Has it always been like this? It may not even be a suitable
stat for your particular boiler. Who supplied/installed it? Mechanical stats
usually have a 3-wire connection - live, switched live and neutral. The
neutral connection provides a return for the accelerator heater (a small
resistor which gets warm when the stat is supplying power to the boiler, and
which reduces the hysteresis). But that pre-supposes that the stat is
switching mains - but some combis have only a low voltage signal going to
the stat, so the accelerator resistor wouldn't work even if connected.

Second question: Would replacing this thermostat with a wireless
digital thermostat improve the situation? There is of course the added
advantage of being able to move the thermostat around the house at our
convenience.

Yes. It doesn't necessarily have to be wireless if it's a direct replacement
for the existing stat - although you couldn't move it around unless it's
wireless. A digital stat is much cleverer than a mechanical stat, and will
adjust the ratio of on-off times to keep the temperature very close to the
target. Digital stats also invariably have 'voltage-free' contacts, and
don't care whether they're switching mains or low voltage. N.B they *don't*
have accelerator resistors so, if there is a neutral wire on the old stat,
it must be taped off safely and *not* connected to anything unless you want
an expensive bang when the stat switches.

Third question: Can it be done? Is it easily DIY able. I’m fairly
adept at these sorts of things but this is not an area I’ve looked at
before.


Yes, it's pretty easy - as long as you heed the warning about the neutral
wire! Non-wireless ones are *very* easy - you identify the live and switched
live (or low voltage equivalent) on the existing stat and wire them to
Common and Demand (or however they're labelled) on the new stat. With a
wireless stat, the base unit replaces the existing stat. Wiring the
switching contacts is much the same, but you also need a mains feed to power
the wireless receiver part.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

On Thu, 13 Nov 2008 21:05:14 +0000, Roger Mills wrote:

In an earlier contribution to this discussion, beamer
wrote:

Hi All,

An easy question for you knowledgeable people!!

We have a elderly but functional combi boiler (in the kitchen) with a
mechanical thermostat in the hallway.

The problem I have is that the range from where the thermostat switches
on the heating to where it switches off the boiler is enormous. For
example, we either freeze or we get roasted! Keeping a steady
temperature in the house is near impossible.

I appreciate that the range of the thermostat shouldnÂ’t be too narrow.

At the moment the thermostat is used as more of an on off switch.

First Question: Is it possible that the mechanical thermostat is
faulty?

Yes, it sounds as if your stat has excessive hysteresis - assuming that
it's working at all. Has it always been like this? It may not even be a
suitable stat for your particular boiler. Who supplied/installed it?
Mechanical stats usually have a 3-wire connection - live, switched live
and neutral. The neutral connection provides a return for the
accelerator heater (a small resistor which gets warm when the stat is
supplying power to the boiler, and which reduces the hysteresis). But
that pre-supposes that the stat is switching mains - but some combis
have only a low voltage signal going to the stat, so the accelerator
resistor wouldn't work even if connected.

Second question: Would replacing this thermostat with a wireless
digital thermostat improve the situation? There is of course the added
advantage of being able to move the thermostat around the house at our
convenience.

Yes. It doesn't necessarily have to be wireless if it's a direct
replacement for the existing stat - although you couldn't move it around
unless it's wireless. A digital stat is much cleverer than a mechanical
stat, and will adjust the ratio of on-off times to keep the temperature
very close to the target. Digital stats also invariably have
'voltage-free' contacts, and don't care whether they're switching mains
or low voltage. N.B they *don't* have accelerator resistors so, if there
is a neutral wire on the old stat, it must be taped off safely and *not*
connected to anything unless you want an expensive bang when the stat
switches.

Third question: Can it be done? Is it easily DIY able. IÂ’m fairly adept
at these sorts of things but this is not an area IÂ’ve looked at before.


Yes, it's pretty easy - as long as you heed the warning about the
neutral wire! Non-wireless ones are *very* easy - you identify the live
and switched live (or low voltage equivalent) on the existing stat and
wire them to Common and Demand (or however they're labelled) on the new
stat. With a wireless stat, the base unit replaces the existing stat.
Wiring the switching contacts is much the same, but you also need a
mains feed to power the wireless receiver part.


The receiver unit for a wireless unit which requires line, neutral and
switched is a direct replacement for a standard non-digital thermostat.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html

On 13 Nov, 20:16, beamer wrote:
Hi All,

An easy question for you knowledgeable people!!

We have a elderly but functional combi boiler (in the kitchen) with a
mechanical thermostat in the hallway.

The problem I have is that the range from where the thermostat
switches on the heating to where it switches off the boiler is
enormous. For example, we either freeze or we get roasted! Keeping a
steady temperature in the house is near impossible.

I appreciate that the range of the thermostat shouldn’t be too narrow.

At the moment the thermostat is used as more of an on off switch.

First Question: Is it possible that the mechanical thermostat is
faulty?

Second question: Would replacing this thermostat with a wireless
digital thermostat improve the situation? There is of course the added
advantage of being able to move the thermostat around the house at our
convenience.

Third question: Can it be done? Is it easily DIY able. I’m fairly
adept at these sorts of things but this is not an area I’ve looked at
before.

Boiler: Ferroli Modena 102
Thermostat: SunVic TLX

Thanks.

I too have a pretty old and inefficient boiler and had a mechanical
thermostat which I swapped for a pretty simple digital (not wireless)
job about 6 months ago. This has made a huge difference to the
stability of the temperature around the house, so if yours is a
similar situation, I'd definitely recommend it. Clearly, the wireless
one would let you experiment and find the perfect location for your
house. Now, if I can just find a way to stop the mother in law
tinkering with it when she comes to visit....

"GMM" wrote in message
...
On 13 Nov, 20:16, beamer wrote:
Hi All,

An easy question for you knowledgeable people!!

We have a elderly but functional combi boiler (in the kitchen) with a
mechanical thermostat in the hallway.

The problem I have is that the range from where the thermostat
switches on the heating to where it switches off the boiler is
enormous. For example, we either freeze or we get roasted! Keeping a
steady temperature in the house is near impossible.

I appreciate that the range of the thermostat shouldn’t be too narrow.

At the moment the thermostat is used as more of an on off switch.

First Question: Is it possible that the mechanical thermostat is
faulty?

Second question: Would replacing this thermostat with a wireless
digital thermostat improve the situation? There is of course the added
advantage of being able to move the thermostat around the house at our
convenience.

Third question: Can it be done? Is it easily DIY able. I’m fairly
adept at these sorts of things but this is not an area I’ve looked at
before.

Boiler: Ferroli Modena 102
Thermostat: SunVic TLX

Thanks.

I too have a pretty old and inefficient boiler and had a mechanical
thermostat which I swapped for a pretty simple digital (not wireless)
job about 6 months ago. This has made a huge difference to the
stability of the temperature around the house, so if yours is a
similar situation, I'd definitely recommend it. Clearly, the wireless
one would let you experiment and find the perfect location for your
house. Now, if I can just find a way to stop the mother in law
tinkering with it when she comes to visit....

I absolutely agree - a modern digital one has a closer control and having a
programmable one gives a smooth transition between time periods. Best £27 I
ever spent.

In article
,
beamer wrote:
We have a elderly but functional combi boiler (in the kitchen) with a
mechanical thermostat in the hallway.

The problem I have is that the range from where the thermostat
switches on the heating to where it switches off the boiler is
enormous. For example, we either freeze or we get roasted! Keeping a
steady temperature in the house is near impossible.

Well either the thermostat is faulty with too large hysteresis - the
difference between switch on and switch off temp - or it's simply in the
wrong position. Personally I think it's best located in the living area -
although of course this can give other problems if you have a lot of
people in there etc.

--
*The severity of the itch is proportional to the reach *

Dave Plowman London SW
To e-mail, change noise into sound.