UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions.

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1   Report Post  
Mark Trueman
 
Posts: n/a
Default Adding Room Stat

Hi,

Current system - gravity HW, pumped CH. HW must be on for CH to be on. Runs
off a Drayton Lifestyle LP241 timer. No stats or TRVs on rads, when its on,
its on full blast.

Anyway, im thinking about adding a room stat to try to control the temp a
bit better. Didnt mind it getting to 25 degrees previously, but now my new
marine fish tank is not liking the increase in room temp.

Anyway, i digress. Looking at installing the Drayton Digistat 2. Looks easy
enough to wire up from looking at the LP241 instructions.

What i want to know is; is there a better/cheaper alternative room stat (24
hour version is fine, 7 day version is even better). And if there is, is the
wiring likely to be the same?

Regards

Mark


  #2   Report Post  
Christian McArdle
 
Posts: n/a
Default

What i want to know is; is there a better/cheaper alternative room stat
(24
hour version is fine, 7 day version is even better). And if there is, is

the
wiring likely to be the same?


Almost any wired programmable room thermostat will have simple contacts and
are wired up in the same manner. A very few have permanent L and N for
power, but the overwhelming majority are battery powered using latching
relays.

There's a huge variety of designs to choose from at various prices,
appearances, sizes, shapes and features.

Christian.


  #3   Report Post  
Set Square
 
Posts: n/a
Default

In an earlier contribution to this discussion,
Mark Trueman wrote:

Hi,

Current system - gravity HW, pumped CH. HW must be on for CH to be
on. Runs off a Drayton Lifestyle LP241 timer. No stats or TRVs on
rads, when its on, its on full blast.

Anyway, im thinking about adding a room stat to try to control the
temp a bit better. Didnt mind it getting to 25 degrees previously,
but now my new marine fish tank is not liking the increase in room
temp.

Anyway, i digress. Looking at installing the Drayton Digistat 2.
Looks easy enough to wire up from looking at the LP241 instructions.

What i want to know is; is there a better/cheaper alternative room
stat (24 hour version is fine, 7 day version is even better). And if
there is, is the wiring likely to be the same?

Regards

Mark


With your existing setup, all you can really do with a room stat is switch
the pump on and off - so, whenever heating is selected by the main
programmer, the boiler will cycle on its own stat - and the DHW will
continue to get hot(ter) by gravity circulation.

A room stat will help to stop the house from getting too hot - but it won't
prevent the boiler from wasting engergy by cycling needlessly, nor will it
prevent the DHW from overheating.

If you're wishing to improve the overall control of your system, you should
seriously consider installing a zone valve in the gravity HW circuit and a
cylinder stat on the hot water cylinder, in order to convert it into a
C-Plan system. [See http://content.honeywell.com/uk/homes/systems.htm ]

This will provide a boiler interlock to ensure that the boiler only runs
when needed - and will provide much better control over DHW temperature.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.


  #4   Report Post  
Christian McArdle
 
Posts: n/a
Default

With your existing setup, all you can really do with a room stat is switch
the pump on and off - so, whenever heating is selected by the main
programmer, the boiler will cycle on its own stat - and the DHW will
continue to get hot(ter) by gravity circulation.


That isn't quite true. On an old boiler setup like this, you would set the
programmable stat to cut power to the boiler, so it won't short cycle. Even
without any additional zone valves at all, you can install a cylinder stat.

The main disadvantages compared to a zone valved system would be:
1. Loss of temperature control of HWC when space heating is called for (but
only when the thermostat is active, not just because CH is on).
2. Possibility of parasitic gravity circulation on heating when only HW
called for.

It still won't comply with Part L1, but it will be massively better than
before, for just the cost of two thermostats and a bit of cable.

Christian.


  #5   Report Post  
Set Square
 
Posts: n/a
Default

In an earlier contribution to this discussion,
Christian McArdle wrote:

With your existing setup, all you can really do with a room stat is
switch the pump on and off - so, whenever heating is selected by the
main programmer, the boiler will cycle on its own stat - and the DHW
will continue to get hot(ter) by gravity circulation.


That isn't quite true. On an old boiler setup like this, you would
set the programmable stat to cut power to the boiler, so it won't
short cycle. Even without any additional zone valves at all, you can
install a cylinder stat.

But surely, if you do this without additional relays, you have to power the
boiler and pump from the same feed - effectively connecting them together.
When (in the summer, say) you turn the boiler on to get DWH, the pump will
come on too.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.




  #6   Report Post  
Christian McArdle
 
Posts: n/a
Default

But surely, if you do this without additional relays, you have to power
the
boiler and pump from the same feed - effectively connecting them together.
When (in the summer, say) you turn the boiler on to get DWH, the pump will
come on too.


Well, one relay will be required, now you come to think of it, although no
doubt someone will come up with a clever relay-less design if we wait long
enough, using the NC terminals of the cylinder stat.

Christian.


  #7   Report Post  
Mark Trueman
 
Posts: n/a
Default


"Set Square" wrote in message
...
In an earlier contribution to this discussion,
Mark Trueman wrote:

Hi,

Current system - gravity HW, pumped CH. HW must be on for CH to be
on. Runs off a Drayton Lifestyle LP241 timer. No stats or TRVs on
rads, when its on, its on full blast.

Anyway, im thinking about adding a room stat to try to control the
temp a bit better. Didnt mind it getting to 25 degrees previously,
but now my new marine fish tank is not liking the increase in room
temp.

Anyway, i digress. Looking at installing the Drayton Digistat 2.
Looks easy enough to wire up from looking at the LP241 instructions.

What i want to know is; is there a better/cheaper alternative room
stat (24 hour version is fine, 7 day version is even better). And if
there is, is the wiring likely to be the same?

Regards

Mark


With your existing setup, all you can really do with a room stat is switch
the pump on and off - so, whenever heating is selected by the main
programmer, the boiler will cycle on its own stat - and the DHW will
continue to get hot(ter) by gravity circulation.


Which i think it does now anyway, we tend to set the boiler to "1" (its an
old baxi back boiler), and let it heat the water as it sees fit.

If i install the stat, is this no longer going to happen?


A room stat will help to stop the house from getting too hot - but it
won't
prevent the boiler from wasting engergy by cycling needlessly, nor will it
prevent the DHW from overheating.

If you're wishing to improve the overall control of your system, you
should
seriously consider installing a zone valve in the gravity HW circuit and a
cylinder stat on the hot water cylinder, in order to convert it into a
C-Plan system. [See http://content.honeywell.com/uk/homes/systems.htm ]

This will provide a boiler interlock to ensure that the boiler only runs
when needed - and will provide much better control over DHW temperature.


Will look into this, thanks.

Picked up a Digistat 3 tonight, going to fit it at the weekend

Mark


  #8   Report Post  
Set Square
 
Posts: n/a
Default

In an earlier contribution to this discussion,
Mark Trueman wrote:

"Set Square" wrote in message
...

With your existing setup, all you can really do with a room stat is
switch the pump on and off - so, whenever heating is selected by the
main programmer, the boiler will cycle on its own stat - and the DHW
will continue to get hot(ter) by gravity circulation.


Which i think it does now anyway, we tend to set the boiler to "1"
(its an old baxi back boiler), and let it heat the water as it sees
fit.

If i install the stat, is this no longer going to happen?

A room stat on its own won't fix it - although it will prevent the radiators
from getting hot when they're not needed.

The problem with having no controls on the DHW temperature is that you can't
run the hot water and radiators at different temperatures. Ideally, the
water going to the radiators needs to be at about 80 degC - which means that
the boiler needs to run at this temperature. However, this will result in
the DHW being heated to approaching 80 degC - but it needs to be limited to
60 degC, otherwise there's a severe risk of scalding. If you run the boiler
cooler to limit the hot water temperature, the radiators won't get hot
enough.

If you control the gravity hot water flow in the way I suggested in my
previous post (by using a zone valve and cylinder stat) you can have the
best of both worlds - hot radiators without the DHW getting too hot. You
also get the added bonus that it shuts the boiler off when both CH and DWH
demands are satisfied, thus saving energy (and money!).
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.


  #9   Report Post  
Mark Trueman
 
Posts: n/a
Default


"Set Square" wrote in message
...
In an earlier contribution to this discussion,
Mark Trueman wrote:

"Set Square" wrote in message
...

With your existing setup, all you can really do with a room stat is
switch the pump on and off - so, whenever heating is selected by the
main programmer, the boiler will cycle on its own stat - and the DHW
will continue to get hot(ter) by gravity circulation.


Which i think it does now anyway, we tend to set the boiler to "1"
(its an old baxi back boiler), and let it heat the water as it sees
fit.

If i install the stat, is this no longer going to happen?

A room stat on its own won't fix it - although it will prevent the
radiators
from getting hot when they're not needed.

The problem with having no controls on the DHW temperature is that you
can't
run the hot water and radiators at different temperatures. Ideally, the
water going to the radiators needs to be at about 80 degC - which means
that
the boiler needs to run at this temperature. However, this will result in
the DHW being heated to approaching 80 degC - but it needs to be limited
to
60 degC, otherwise there's a severe risk of scalding. If you run the
boiler
cooler to limit the hot water temperature, the radiators won't get hot
enough.

If you control the gravity hot water flow in the way I suggested in my
previous post (by using a zone valve and cylinder stat) you can have the
best of both worlds - hot radiators without the DHW getting too hot. You
also get the added bonus that it shuts the boiler off when both CH and DWH
demands are satisfied, thus saving energy (and money!).


You have just summed up my problems well. Yes, the water gets too flipping
hot in the winter as we have to turn the temp up on the boiler in order to
get the rads up to a nice temp

So im looking at converting to a c-plan, which doesnt look too hard, once i
get my head round the electrics. I think the way this is wired up currently
is a total botch job so it may take some working out!! Is there an easy way
to wire in the cylinder stat and 2 port valve by just using the connections
available to me in the LP241 controller. This would also make wiring runs a
lot easier. Connecting anything to the pump is definitely out of the
question, as its not easily accessible.

Im pretty competent at electrics and plumbing but havent ever done any ch
wiring before so any tips would be happily received



  #10   Report Post  
Set Square
 
Posts: n/a
Default

In an earlier contribution to this discussion,
Mark Trueman wrote:


You have just summed up my problems well. Yes, the water gets too
flipping hot in the winter as we have to turn the temp up on the
boiler in order to get the rads up to a nice temp

So im looking at converting to a c-plan, which doesnt look too hard,
once i get my head round the electrics. I think the way this is wired
up currently is a total botch job so it may take some working out!!
Is there an easy way to wire in the cylinder stat and 2 port valve by
just using the connections available to me in the LP241 controller.


Sorry, I'm not familiar with the LP241 controller - but the best way is
often to bring everything together (boiler, pump, valve, thermostats) in a
10-way junction box or wiring centre - similar to that shown in the C-Plan
wiring diagram in http://content.honeywell.com/uk/homes/systems.htm

Even if you can't easily get at the pump, you may be able to get at the
other end of its cable - and divert or extend it into the junction box.

When you fit the zone valve, you'll have to be careful to locate it
somewhere where it won't interfere with the fill and expansion pipes having
clear runs to the boiler. Very close to the cylinder is often a good place -
in either the flow or return pipe, between the coil and the point where the
F or E pipe connects in.

Note also that the zone valve needs to have a change-over (as opposed to
on/off) switch which is independent of the motor connections, and which
switches when the valve is fully open. [Maybe they all have this anyway -
but check to be on the safe side, 'cos it won't work without!]
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.




  #11   Report Post  
Mark Trueman
 
Posts: n/a
Default

OK,

So im just trying to work out how to connect this new stat up (Drayton
Digistat 3)

Its got 3 wires, common, heat satisfied and heat not satisfied. Ideally i
would like to be able to just wire this into the timer control and not have
to do a run to the pump, as the pump is in a stupid position under the floor
and is a pain to get to. Plus there is no junction box, it seems to be wired
up by someone with a deathwish!! Its a Drayton Lifestyle lp241 controller.
Just wanted to check the following....

Im pretty sure that common on the stat can be put into to the "ch on" (pin
4) in the timer, but im not sure about the other 2.

Any help is appreciated before i have to pay someone to do it


  #12   Report Post  
Set Square
 
Posts: n/a
Default

In an earlier contribution to this discussion,
Mark Trueman wrote:

OK,

So im just trying to work out how to connect this new stat up (Drayton
Digistat 3)

Its got 3 wires, common, heat satisfied and heat not satisfied.
Ideally i would like to be able to just wire this into the timer
control and not have to do a run to the pump, as the pump is in a
stupid position under the floor and is a pain to get to. Plus there
is no junction box, it seems to be wired up by someone with a
deathwish!! Its a Drayton Lifestyle lp241 controller. Just wanted to
check the following....

Im pretty sure that common on the stat can be put into to the "ch on"
(pin 4) in the timer, but im not sure about the other 2.

Any help is appreciated before i have to pay someone to do it


There's a very good chance that the wire currently connected to CH ON in the
programmer goes to the pump. You need to connect your stat *in series* with
this pump connection. This means disconnecting the existing wire, connecting
CH ON to Common on the stat, and connecting the disconnected wire - now
floating around in space! - to 'heat not satisfied' on the stat. Don't
connect anything to 'heat satisfied'.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.


  #13   Report Post  
Mark Trueman
 
Posts: n/a
Default



There's a very good chance that the wire currently connected to CH ON in
the
programmer goes to the pump. You need to connect your stat *in series*
with
this pump connection. This means disconnecting the existing wire,
connecting
CH ON to Common on the stat, and connecting the disconnected wire - now
floating around in space! - to 'heat not satisfied' on the stat. Don't
connect anything to 'heat satisfied'.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.



Cheers mate, simple when you know how. That worked a treat. Now i just have
to work out how to wire up the 2 port and the cylinder stat (which i will
buy at the weekend maybe).

Of course, the problem now is that as the central heating is on all the time
(pump is controlled by the stat), the hot water is on constantly. The sooner
i get this cylinder stat and valve in the better i think.

So expect some more questions soon....

Thanks again

Mark


  #14   Report Post  
Set Square
 
Posts: n/a
Default

In an earlier contribution to this discussion,
Mark Trueman wrote:


Cheers mate, simple when you know how. That worked a treat. Now i
just have to work out how to wire up the 2 port and the cylinder stat
(which i will buy at the weekend maybe).

Of course, the problem now is that as the central heating is on all
the time (pump is controlled by the stat), the hot water is on
constantly. The sooner i get this cylinder stat and valve in the
better i think.

The pump is controlled by the stat - but only when the original programmer
tells it to - so you can still have it on only at specified times if you
wish. In other words, if the programmer says "No Heating", then No heating
it is, regardless of what the stat says.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.


  #15   Report Post  
G&M
 
Posts: n/a
Default


"Mark Trueman" wrote in message
...
Hi,

Current system - gravity HW, pumped CH. HW must be on for CH to be on.

Runs
off a Drayton Lifestyle LP241 timer. No stats or TRVs on rads, when its

on,
its on full blast.

Anyway, im thinking about adding a room stat to try to control the temp a
bit better. Didnt mind it getting to 25 degrees previously, but now my new
marine fish tank is not liking the increase in room temp.

Anyway, i digress. Looking at installing the Drayton Digistat 2. Looks

easy
enough to wire up from looking at the LP241 instructions.

What i want to know is; is there a better/cheaper alternative room stat

(24
hour version is fine, 7 day version is even better). And if there is, is

the
wiring likely to be the same?


Cheapest 7 day unit I know is the Maplin one. Has mains rated normally open
and closed contacts.




  #16   Report Post  
mike ring
 
Posts: n/a
Default

"Mark Trueman" wrote in
:


So expect some more questions soon....

Thanks again

Mark


One from me, Mark; where do you actually get the drayton stat - it looks
the right size and shape to replace my mechanical one, but there seem few
suppliers, and I worry about new web suppliers (tho' the ones I _have_
tried have been fine....ish

mike
Reply
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Combi Boiler and Room Thermostats Daern's Instant Fortress UK diy 5 May 10th 04 11:23 AM
Update: Adding a wireless room thermostat (help needed) JH UK diy 9 January 18th 04 02:39 PM


All times are GMT +1. The time now is 12:31 PM.

Powered by vBulletin® Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 DIYbanter.
The comments are property of their posters.
 

About Us

"It's about DIY & home improvement"