Does a combi bolier need to have a room thermostat or can it run off just a time clock?

davethediver wrote on 02. Feb 2011 at 22:58:

Does a combi bolier need to have a room thermostat or can it run off just a time clock?

I am not sure about the question, yes it will have a time clock, but surly also a thermostat...what are you trying to do, if you only want to control the heating by a time clock just turn the stat up high and set the clock.....
:-/ ::)

davethediver wrote on 02. Feb 2011 at 22:58:

Does a combi bolier need to have a room thermostat or can it run off just a time clock?

My combi has a thermostat near the stairwell. Individual rooms are then controlled by the rad valves.

The boiler did have an integral mechanical clock which broke :( there is no house stat but all the rads do have TRV's on. I have attempted to wire in a new single chanel honeywell timeclock and all though it has power to the timer i can't get it to operate the heating >:(

I'm not a sparky so its a bit of trial and error or help off OOF ;D ;D it did work without a housestat just don't know what im doing wrong with this timer :-[ :-[

I believe current regs state that there should be a thermostat in one room in addition to TRVs in all others to prevent the boiler working when no heat is called for.

As to why it doesn't work, it would depend on the specific boiler so try and find the installation manual (should be left with the installation). Failing that download one from the web.

Normally there will be provision for either a mains power input from a timeswitch plus room thermostat or a set of contacts which close when the CH is calling for heat.

Kevin

Ahh- if the boiler has an internal timeswitch which is broken can you be sure it's calling for heat or has it failed in the "off" position? Does the boiler fire up if you select constant CH?

Might be easier to source a replacement timeswitch module for the boiler, TBH.

Kevin

Kevin Wood wrote on 03. Feb 2011 at 00:12:

Ahh- if the boiler has an internal timeswitch which is broken can you be sure it's calling for heat or has it failed in the "off" position? Does the boiler fire up if you select constant CH? Might be easier to source a replacement timeswitch module for the boiler, TBH. Kevin

The boiler does fire up if the timed/constant switch is placed on constant. I,m pretty certain its something to do with the switched live connection as said electrics ain't my stong point.

Part L of the building regs does state that a CH system should have a temperature contol as well as a time control and that bedroom rads have TRV's on them.

Going to look a bit of a tool at work if i have to ask one of the engineers (work for a large domestic heating firm) :-[ :-[

davethediver wrote on 03. Feb 2011 at 00:31:

[quote author=4B6576696E5F576F6F64000 link=1296687538/5#5 date=1296691968]Ahh- if the boiler has an internal timeswitch which is broken can you be sure it's calling for heat or has it failed in the "off" position? Does the boiler fire up if you select constant CH? Might be easier to source a replacement timeswitch module for the boiler, TBH.Kevin

The boiler does fire up if the timed/constant switch is placed on constant. I,m pretty certain its something to do with the switched live connection as said electrics ain't my stong point.

Part L of the building regs does state that a CH system should have a temperature contol as well as a time control and that bedroom rads have TRV's on them.

Going to look a bit of a tool at work if i have to ask one of the engineers (work for a large domestic heating firm) :-[ :-[/quote]





Then you couldn't be in a better place to obtain a replacement surely, & at 'cost'? :y

PhilRich wrote on 03. Feb 2011 at 07:45:

davethediver wrote on 03. Feb 2011 at 00:31: [quote author=4B6576696E5F576F6F64000 link=1296687538/5#5 date=1296691968]Ahh- if the boiler has an internal timeswitch which is broken can you be sure it's calling for heat or has it failed in the "off" position? Does the boiler fire up if you select constant CH? Might be easier to source a replacement timeswitch module for the boiler, TBH.Kevin The boiler does fire up if the timed/constant switch is placed on constant. I,m pretty certain its something to do with the switched live connection as said electrics ain't my stong point. Part L of the building regs does state that a CH system should have a temperature contol as well as a time control and that bedroom rads have TRV's on them. Going to look a bit of a tool at work if i have to ask one of the engineers (work for a large domestic heating firm) :-[ :-[/quote] Then you couldn't be in a better place to obtain a replacement surely, & at 'cost'? :y

Yep, and a manual. What model of boiler is it? Worth looking for documentation online?

Kevin

You will be hard pushed to find a real engineer in a domestic heating firm  :y ;D

Post up the boiler make and model and we will see what we can do

Boiler is an old Potterton Lynx 2 and time clock is a simple 1 day 1 channel honeywell unit.

And Mark you are of course right the only one i'd class as a real engineer (40yrs in the trade and a very knowlegable guy on most things) is on sodding holiday and i don't want any of the others coming round to 'fix it' for me because thats One point to them and None to me ;D ;D

davethediver wrote on 03. Feb 2011 at 12:32:

Boiler is an old Potterton Lynx 2 and time clock is a simple 1 day 1 channel honeywell unit. And Mark you are of course right the only one i'd class as a real engineer (40yrs in the trade and a very knowlegable guy on most things) is on sodding holiday and i don't want any of the others coming round to 'fix it' for me because thats One point to them and None to me ;D ;D

The engineer designed the boiler, technicians repair them and fitters install them....  ;D

Heres the installation manual:

http://www.partsarena.co.uk/baxi/System/DATA/Dx/DS1/installation/2511/I19-2511/I19-2511.htm

It shows how the timer needs to be wired (dead easy to do)

What timer are you fitting and I will do a quick connection list for you.

For combi boiler use a programmable room stat.Quite simple to fit just a single 'channel' 2 wires,basically acts like a switch.

Just fitted one for my son Honeywell cm907,cost me about  60 quid there are cheaper ones.

Just look up your boiler instructions to get the right connections.

Just looked at the wiring diagram and you would use terminals 3 and 4 and remove the link.The honeywell stat does not require a permanent live or neutral as it is battery operated.

Marks DTM Calib wrote on 03. Feb 2011 at 13:10:

What timer are you fitting and I will do a quick connection list for you.

Its a Honeywell ST9100a.

TIA Dave