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Paul
 
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Default Replacing old Honeywell thermostat

Hi,

I've just moved into a new house and found that the cover for my room
thermostat is broken, so I thought I'd better replace it. I don't know
what the model number is, but there is a simple wiring diagram on hte
inside (live, neutral and the wire to the central heating controller).
The terminal that connects to the central heating is number 3 and
marked 20(4)A - do I need to get a new thermostat with the same
rating, or would a 10(4)A be up to the job, as that's the highest I
can find locally. If this isn't enough information, let me know what
else is needed for me to find out.

Thanks,

Paul
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IMM
 
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Default Replacing old Honeywell thermostat


"Paul" wrote in message
om...
Hi,

I've just moved into a new house and found that the cover for my room
thermostat is broken, so I thought I'd better replace it. I don't know
what the model number is, but there is a simple wiring diagram on hte
inside (live, neutral and the wire to the central heating controller).
The terminal that connects to the central heating is number 3 and
marked 20(4)A - do I need to get a new thermostat with the same
rating, or would a 10(4)A be up to the job, as that's the highest I
can find locally. If this isn't enough information, let me know what
else is needed for me to find out.



That will be fine if running a normal gas boiler, pump, zone valves.
Running an electric heating system? Then it is a case of assessing the
current loading.


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Christian McArdle
 
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Default Replacing old Honeywell thermostat

marked 20(4)A - do I need to get a new thermostat with the same
rating, or would a 10(4)A be up to the job, as that's the highest I
can find locally.


If this is for a normal central heating system, then the entire system will
be fused at 3A, so anything that can cope with that would be fine.

Christian.



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Lurch
 
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Default Replacing old Honeywell thermostat

On Tue, 2 Mar 2004 09:46:55 -0000, in uk.d-i-y "IMM"
strung together this:


"Paul" wrote in message
. com...
Hi,

I've just moved into a new house and found that the cover for my room
thermostat is broken, so I thought I'd better replace it. I don't know
what the model number is, but there is a simple wiring diagram on hte
inside (live, neutral and the wire to the central heating controller).
The terminal that connects to the central heating is number 3 and
marked 20(4)A - do I need to get a new thermostat with the same
rating, or would a 10(4)A be up to the job, as that's the highest I
can find locally. If this isn't enough information, let me know what
else is needed for me to find out.



That will be fine if running a normal gas boiler, pump, zone valves.
Running an electric heating system? Then it is a case of assessing the
current loading.

If it's electric I doubt all the heaters will run through one stat,
it'd be more than 20A. Any standard room stat will suffice.
...

SJW
A.C.S. Ltd.
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IMM
 
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Default Replacing old Honeywell thermostat


"Lurch" wrote in message
...
On Tue, 2 Mar 2004 09:46:55 -0000, in uk.d-i-y "IMM"
strung together this:


"Paul" wrote in message
. com...
Hi,

I've just moved into a new house and found that the cover for my room
thermostat is broken, so I thought I'd better replace it. I don't know
what the model number is, but there is a simple wiring diagram on hte
inside (live, neutral and the wire to the central heating controller).
The terminal that connects to the central heating is number 3 and
marked 20(4)A - do I need to get a new thermostat with the same
rating, or would a 10(4)A be up to the job, as that's the highest I
can find locally. If this isn't enough information, let me know what
else is needed for me to find out.



That will be fine if running a normal gas boiler, pump, zone valves.
Running an electric heating system? Then it is a case of assessing the
current loading.

If it's electric I doubt all the heaters will run through one stat,
it'd be more than 20A. Any standard room stat will suffice.


It could be zoned or whatever. The main point is assessing the loading and
getting a stat to suit.




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Michael Chare
 
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Default Replacing old Honeywell thermostat

"Paul" wrote in message
om...
Hi,

I've just moved into a new house and found that the cover for my room
thermostat is broken, so I thought I'd better replace it. I don't know
what the model number is, but there is a simple wiring diagram on hte
inside (live, neutral and the wire to the central heating controller).
The terminal that connects to the central heating is number 3 and
marked 20(4)A - do I need to get a new thermostat with the same
rating, or would a 10(4)A be up to the job, as that's the highest I
can find locally. If this isn't enough information, let me know what
else is needed for me to find out.


It depends what load the thermostat is connected to.

20(4)A is a 20 amp resistive load / 4 amp inductive.

What size fuse does the central heating system use, this should give you some
idea of the load.

You might want to consider a programmable thermostat. They cost more but as
well as allowing you to vary the temperature during the day with maybe a
different program at weekends, they also provide a much more precise control of
the temperature.

Michael Chare


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Paul
 
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Default Replacing old Honeywell thermostat

It's just a simple Y-plan, gas heating system for a semi-detached
house, so it sounds like it would work. Thanks for your help (also
goes out to the rest of the thread!)

Paul
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Woody
 
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Default Replacing old Honeywell thermostat


"Paul" wrote in message
om...
Hi,

I've just moved into a new house and found that the cover for my room
thermostat is broken, so I thought I'd better replace it. I don't know
what the model number is, but there is a simple wiring diagram on hte
inside (live, neutral and the wire to the central heating controller).
The terminal that connects to the central heating is number 3 and
marked 20(4)A - do I need to get a new thermostat with the same
rating, or would a 10(4)A be up to the job, as that's the highest I
can find locally. If this isn't enough information, let me know what
else is needed for me to find out.

Thanks,

Paul


The most your heating will take is about 2A - the boiler takes about 50W and
the pump usually about 200W, but as the pump is a wholly inductive load the
contacts need to be slightly higher rated to allow for minor arcing as the
contacts open.

Your don't have to replace like for like. Modern 'stats are electronic with
a timer built in so that you can have different temperatures at different
times of the day. So long as it switches as you require it will meet the
need.


--

Woody




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Dave Liquorice
 
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Default Replacing old Honeywell thermostat

On Tue, 9 Mar 2004 09:06:19 -0000, Woody wrote:

The most your heating will take is about 2A - the boiler takes about
50W and the pump usually about 200W,


Depends on the system the OP doesn't say what the boiler is, mine
takes about 150W (oil pressure jet) I doubt my fathers takes more than
10W for the gas valve, (open flued, no fans etc). My pumps, normal
size for domestic properties have a maximum of 95W.

but as the pump is a wholly inductive load the contacts need to be
slightly higher rated to allow for minor arcing as the contacts
open.


This is true, kust ensure that the figure enclosed by brackets in the
rating is large enough. Most are "(3A)" which is about 700W so ample
for nearly every domestic CH system.

Your don't have to replace like for like. Modern 'stats are
electronic with a timer built in so that you can have different
temperatures at different times of the day. So long as it switches
as you require it will meet the need.


Going for a programable room stat is probably a very good idea rather
than just replace with a normal one. They are excellent devices and
really do improve the comfort of the house. A few pounds more but well
worth it. Many are now on the market but the cheaper ones tend to
loose features and/or temperature settings.

Personally I'd look for one that is 7 day programable (yes you may be
a 9-5 M-F wage slave now but will you always be?) with 6 temperature
settings/day and "optimum start". Optimum start is where the stat
looks at the current room temp and starts the system a variable amount
of time before (normally) the first set temperature such that that
temperature is met by the required time.

--
Cheers
Dave. pam is missing e-mail



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