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Post by Clinton Cool on May 30, 2024 10:59:09 GMT
I'm in the process of fitting a room thermostat to control my central heating. It's on a suitable place on the wall now, I've routed the wire.
Confusion now over terms. 3 core is needed. There's a live, neutral and switched live. Or should I say, the boiler manual refers to a switched live. The intructions with the thermostat refer to live, neutral and 'call for heat'. Would it be right to assume that 'switched live' is the same as 'call for heat'? Also, the thermostat instructions refer to a 3a fuse being required but it's not clear whether this should be on the neutral or live wire. Actually, it's not clear whether it's needed within the thermostat circuit at all, or within the boiler circuit.
Anyone?
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Post by Telemachus on May 30, 2024 12:19:46 GMT
Yes switched live and call for heat will be the same thing. Any fuse should be in the live, not the neutral. There just needs to be a 3A fuse between the consumer unit ring main breaker (or separate breaker for the CH) and the thermostat. So if the live for the thermostat is connected directly to the mains ring (which is unlikely) then a separate fuse would be required. But anyway a thermostat shouldn’t be connected directly to the mains, it should be via a switched fused outlet, But more likely, the thermostat live will be connected to a live within the boiler and thus the thermostat wiring will be protected by whatever fuse is in the boiler supply. Again, normal practice would be to power the boiler from a switched fused outlet or a 13A plug with appropriately rated fuse. I would have thought a boiler doesn’t need more than 3A so if the existing boiler fuse is 3A then you are sorted. If it is an electric boiler then you would need a separate fuse for the thermostat.
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Post by Clinton Cool on May 30, 2024 12:36:01 GMT
That's great, thanks. The boiler has dedicated terminals for a room thermostat, which I'll connect it to so I guess that then means the thermostat is protected by the fuse in the boiler. I'll now check that the boiler is protected by a 3a fuse.
There's an on/off switch near the boiler so I guess I'll turn the power off at the mains, open this up and check that the fuse in it is 3a.
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Post by brummieboy on May 30, 2024 15:55:48 GMT
Which thermostat do you have and which boiler? if the boiler has dedicated terminals for the room stat, then you need a feed from one of those terminals to the thermostat common pole and one lead back from the demand terminal to the boiler. What voltage is there across the thermostat terminals on the boiler? If 240volt, depending on the thermostat, you may need an earth if it is not double insulated. Also some thermostats need a neutral to feed back from a heat anticipator. If it is an electronic thermostat that is mains fed, and the boiler is 24 volt, then you may need a dedicated 240 volt feed for the stat and 2 core for the control wires.
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Post by Clinton Cool on May 30, 2024 16:29:23 GMT
The thermostat is a Drayton RTS 1 230v. Boiler is a very old Worcester 24i RSF.
Regarding an earth the instructions say: 'the thermostat is for fixed wiring only and is double insulated, the earthing continuity (loop) terminal is only provided for convenience.
I've checked, the boiler is protected by a 3a fuse at the switch.
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Post by brummieboy on May 30, 2024 17:47:46 GMT
The thermostat is a Drayton RTS 1 230v. Boiler is a very old Worcester 24i RSF. Regarding an earth the instructions say: 'the thermostat is for fixed wiring only and is double insulated, the earthing continuity (loop) terminal is only provided for convenience. I've checked, the boiler is protected by a 3a fuse at the switch. You will need a 3 core cable to your thermostat connections as follows: On the boiler, termnial block X2, remove the link from Ri and RL Connect RL to L on the thermostat Connect RN to terminal on the thermostat. Connect RN to Neutral on the Thermostat. It will work without the neutral connection, but the switching differential will be varied and wide. The neutral completes a circuit to an internal het anticipator. The boiler fuse protects the circuit.
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Post by Clinton Cool on May 30, 2024 17:59:48 GMT
The thermostat is a Drayton RTS 1 230v. Boiler is a very old Worcester 24i RSF. Regarding an earth the instructions say: 'the thermostat is for fixed wiring only and is double insulated, the earthing continuity (loop) terminal is only provided for convenience. I've checked, the boiler is protected by a 3a fuse at the switch. You will need a 3 core cable to your thermostat connections as follows: On the boiler, termnial block X2, remove the link from Ri and RL Connect RL to L on the thermostat Connect RN to terminal on the thermostat. Connect RN to Neutral on the Thermostat. It will work without the neutral connection, but the switching differential will be varied and wide. The neutral completes a circuit to an internal het anticipator. The boiler fuse protects the circuit. Thanks for that. Did you get it off the 24i RSF manual online? I looked at this. The three terminals to the left of the connections for the thermostat are already populated by wires. These will be the 'programmer connections' shown on the picture in the manual. There is a time clock with the boiler and little nibs you can push in to set the time for the boiler to start/ stop. I guess this is what they describe as a 'programmer'. I'm guessing now. I think I need to leave the programmer wires in place and wire the thermostat as you suggested. I guess I can then play around with the 'timed heat' 'constant heat' button to see whether the thermostat overrides the programmer, or it's the other way round. Sound OK?
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Post by brummieboy on May 30, 2024 18:38:28 GMT
The programmer (your clock with the nibs in) should be in the other 3 terminals on X2 , CN, C1 and CL. What do you have in thase connections. The thermostat is effectively powered by the programmer, and it is just another switch in the programmer switched circuit, so yes, it will overide the programmer if that is active, but if the programmer goes off then the thermostat will also be dead. How many connections do you have on the X2 block?
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Post by Telemachus on May 30, 2024 18:46:25 GMT
The thermostat is a Drayton RTS 1 230v. Boiler is a very old Worcester 24i RSF. Regarding an earth the instructions say: 'the thermostat is for fixed wiring only and is double insulated, the earthing continuity (loop) terminal is only provided for convenience. I've checked, the boiler is protected by a 3a fuse at the switch. You will need a 3 core cable to your thermostat connections as follows: On the boiler, termnial block X2, remove the link from Ri and RL Connect RL to L on the thermostat Connect RN to terminal on the thermostat. Connect RN to Neutral on the Thermostat. It will work without the neutral connection, but the switching differential will be varied and wide. The neutral completes a circuit to an internal het anticipator. The boiler fuse protects the circuit. It’s an interesting point whether the heat anticipator is a good idea. Yes it will keep a more even temperature but at the expense of a lot more boiler cycling. I don’t know if the boiler has a minimum short cycle setting but if it does and it’s a while, this might defeat the heat anticipator.
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Post by Clinton Cool on May 30, 2024 19:04:44 GMT
The programmer (your clock with the nibs in) should be in the other 3 terminals on X2 , CN, C1 and CL. What do you have in thase connections. The thermostat is effectively powered by the programmer, and it is just another switch in the programmer switched circuit, so yes, it will overide the programmer if that is active, but if the programmer goes off then the thermostat will also be dead. How many connections do you have on the X2 block? Yes there are 6 possible connections in the X2 block. To the left, the programmer bit, 3 wires are already attached. I assume these are from the clock as the boiler works as it should on timer mode. The other 3 possible connections, to the right, are currently vacant. I plan to connect the 3 wires from the thermostat as you suggested earlier on. I think that's it?
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Post by brummieboy on May 30, 2024 19:06:51 GMT
My edits got lost in the proboards down time. I did not read your post correctly. Yes leave the programmer connections in place. The manual is a little confusing to the layman as it does not show an integrated diagram. The room stat is just another switch in the boiler live and breaks the timer connection when the room is up to temperature. it is only live when the timer switches on. Nick, I'm no electronics expert, but my experience in this occupation tells me that Mr Drayton, along with Mr Honeywell and Mr Satchwell knew a thing or two as all their similar products have this heat anticipator to assist the operation of a bimetallic strip or aneroid bellows. It only operates when the set point of room temperature is reached and will generally give a differential of 1 -2 degrees of room temperature. short cycling settings are only fitted into boiler temperature monitoring circuits and only affect burner operation. Generally they time out at 2-3 minutes, but it is not unusual to encounter 1-2 minutes of burner operation on small circuits. At the business end, the pump still circulates the primary water through the radiators and you never really see the effects of this at the radiators.
Edit to add: wire the stat up to the connections adjacent to the programmer. Dont forget to remove the link between the 2 right hand terminals.
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Post by Clinton Cool on May 30, 2024 19:17:35 GMT
Great, thanks for all the help. I toyed with the idea of getting a new boiler but this one is working fine, so why scrap it? I've booked to go away for 2 months in early January and although we get few frosts here, a prolonged cold spell is always possible.
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Post by Telemachus on May 30, 2024 19:36:06 GMT
Nick, I'm no electronics expert, but my experience in this occupation tells me that Mr Drayton, along with Mr Honeywell and Mr Satchwell knew a thing or two as all their similar products have this heat anticipator to assist the operation of a bimetallic strip or aneroid bellows. It only operates when the set point of room temperature is reached and will generally give a differential of 1 -2 degrees of room temperature. short cycling settings are only fitted into boiler temperature monitoring circuits and only affect burner operation. Generally they time out at 2-3 minutes, but it is not unusual to encounter 1-2 minutes of burner operation on small circuits. At the business end, the pump still circulates the primary water through the radiators and you never really see the effects of this at the radiators. My interest in this point relates to my mother’s ancient CH system which really needs a new boiler. Currently it is a 3 zone system (upstairs, downstairs, hot water) and I’m pretty sure the thermostat doesn’t have (or it isn’t wired) a heat anticipator. It’s a really badly installed system, amongst other things the room stat is in the kitchen very close to the oven! As you will know the (Honeywell) zone valves contain switches that actually send the call for heat (turn on the boiler) and so a lot of short cycling from the thermostat causes the downstairs zone valve to open and close a lot. They are not particularly reliable. I am wondering how to make it better if we get her a new boiler (old boiler is not a condensing boiler). In our house we have Vaillant Vsmart which is internet connected and has load and weather compensation, it’s great but I think all that would be beyond her.
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Post by brummieboy on May 30, 2024 20:08:35 GMT
The short answer is to move the room thermostat. Easily done with wireless units for about £60. No long wiring runs as the wall stat is battery operated. Without knowing what is fitted, if it is old, it could be 'feathering' and a newer unit might solve the problem. www.cityplumbing.co.uk/p/esi-wireless-digital-room-thermostat-with-tpi-es-rterfw/p/740724?lsft=adtype:pla,productchannel:online,storename:,product_id:740724&gad_source=1&gclid=CjwKCAjwx-CyBhAqEiwAeOcTdSZOC36jaeCOe9r3NHnOOoLtgIrVW62BAqLOCGoatrKdzGWkNbPTqhoCWxwQAvD_BwE&gclsrc=aw.ds#fo_c=2832&fo_k=75fb6fdd5e5cfe628081bb0a5edd5f1c&fo_s=gplauk How does it control 3 zones?
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Post by Telemachus on May 30, 2024 20:22:55 GMT
The short answer is to move the room thermostat. Easily done with wireless units for about £60. No long wiring runs as the wall stat is battery operated. Without knowing what is fitted, if it is old, it could be 'feathering' and a newer unit might solve the problem. www.cityplumbing.co.uk/p/esi-wireless-digital-room-thermostat-with-tpi-es-rterfw/p/740724?lsft=adtype:pla,productchannel:online,storename:,product_id:740724&gad_source=1&gclid=CjwKCAjwx-CyBhAqEiwAeOcTdSZOC36jaeCOe9r3NHnOOoLtgIrVW62BAqLOCGoatrKdzGWkNbPTqhoCWxwQAvD_BwE&gclsrc=aw.ds#fo_c=2832&fo_k=75fb6fdd5e5cfe628081bb0a5edd5f1c&fo_s=gplauk How does it control 3 zones? The thermostat doesn't, it just controls the downstairs rads motorised valve. There is a 3 channel timer, pretty sure the upstairs doesn't have a stat but she only has it on for a couple of hours morning and evening. The hot water tank has a stat that operates its motorised valve.
With condensing boilers it does seem a shame not to have load compensation - ie reduction in circulation temperature as the set temp is approached, rather than having a fixed circulation temperature getting turned on and off - but then with the hot water tank there are Legionnaires considerations. It does seem quite hard to design an efficient system that does both rads and DHW, unless it is a combi.
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