Author Topic: Central heating thermostat  (Read 3569 times)

velosam

  • '.....you used to be an apple on a stick.'
Central heating thermostat
« on: October 22, 2018, 10:33:18 am »
I have just bought a house. Turns out that the central heating thermostat only kicks in at 25C!

Is it an easy change to a new one, and any recommendations of what to buy and how to change the whole unit?

thanks

sam

Re: Central heating thermostat
« Reply #1 on: October 22, 2018, 10:48:03 am »
Straight swop?
Get a bicycle. You will never regret it, if you live- Mark Twain

Feanor

  • It's mostly downhill from here.
Re: Central heating thermostat
« Reply #2 on: October 22, 2018, 10:59:53 am »
Very easy to replace.

Only thing to be aware of is that there are 3-wire models ( Live in, switched live out, and Neutral ), and 2-wire models ( no Neutral connection ).
Simplest is to replace like-for-like.


Kim

  • Timelord
Re: Central heating thermostat
« Reply #3 on: October 22, 2018, 11:07:58 am »
If you've got power available at the thermostat location, there's a lot to be said for fitting a wireless unit (the receiver wires in like a normal thermostat), so you can move the controller around to the room you're actually in.  Thermostats often get installed in positions that make the wiring easier, rather than where sensing the temperature is most useful.

Consider internet-of-shit smart stuff, if you're that way inclined.
To ride the Windcheetah, first, you must embrace the cantilever...

Re: Central heating thermostat
« Reply #4 on: October 22, 2018, 11:14:06 am »
Plus some of the newer stats also allow multiple programmes, so for instance a cooler temp weekday mornings when you're getting ready to go to work, but warmer when you get in in the evening, with different profiles at the weekend.

But yes, it's a simple job to wire in the replacement. Even if you just want a simple replacement I'd urge you to get a digital one, which gives much closer control of the temp with much reduced hysteresis.

I used this one

https://www.screwfix.com/p/honeywell-dt90e-digital-room-thermostat-eco/41365
We are making a New World (Paul Nash, 1918)

Re: Central heating thermostat
« Reply #5 on: October 22, 2018, 11:17:42 am »
I got an Amazon Echo last week. Great device.
I have a radio controlled thermostat. The control box is on the wall beside the boiler.
Any ide how wassy/hard it is to replace the thermostat with an Amazon compatible one?
And what brand?  Nest looks nice. Or Hive?
Bad stories welcomed as are good.

Re: Central heating thermostat
« Reply #6 on: October 22, 2018, 11:40:41 am »
Only thing to be aware of is that there are 3-wire models ( Live in, switched live out, and Neutral ), and 2-wire models ( no Neutral connection ).
Simplest is to replace like-for-like.

There are also boilers where the thermostat connection is low voltage DC and they require either a fully mechanical thermostat or a battery powered electronic one.

(On either type, you need to treat the thermostat wires as potentially mains voltage and take appropriate precautions)

tiermat

  • According to Jane, I'm a Unisex SpaceAdmin
Re: Central heating thermostat
« Reply #7 on: October 22, 2018, 11:47:28 am »
I got an Amazon Echo last week. Great device.
I have a radio controlled thermostat. The control box is on the wall beside the boiler.
Any ide how wassy/hard it is to replace the thermostat with an Amazon compatible one?
And what brand?  Nest looks nice. Or Hive?
Bad stories welcomed as are good.

In my mind your options are:

Nest
Nest, or alternatively
Nest.

Yes they are spendy, compared to "dumb" 'stats, but ours saved us ~£1000 in it's first year of use (3 adults (near enough) and a cat in 3 bed detached)

I am guessing the one the OP has is a Honeywell, my experience with them is that, after about 10-15 years they simply become random number generators.  One day your house will be at >30C, the next at <5C, with no rhyme or reason as to why.
I feel like Captain Kirk, on a brand new planet every day, a little like King Kong on top of the Empire State

pdm

  • Sheffield hills? Nah... Just potholes.
Re: Central heating thermostat
« Reply #8 on: October 22, 2018, 12:54:38 pm »
We went for Tado.
As Kim intimates, all the internet controlly things are a compromise and have pluses and minuses.
Our system is great - we have expanded it over the time we have had it to now control every room using wireless radiator thermostat valves; if we are only using 2 rooms, they are the only ones heated. Some rooms are on special timings; eg bathroom for the time we usually use it, bedroom just before bedtime, etc.
Coupled with the smartphone location control ability of this system (if we are both out of the house, the heating goes off; as we approach home, it goes back on before we get there), and the ability to easily set different per room programs for every day of the week if necessary, it is a very powerful system and has saved us a little money on the heating - not quite the "31%" claimed by the manufacturer; more in the region of ~15%, I reckon, looking at previous years usages.
Fitting was dead easy - take old thermostat off, wire up the new one using detailed instructions, sign up for an internet account, download phone app and off you go. On the radiators (if installed) simply unscrew the old TRV and replace with the wireless TRV (plus a readily available adaptor if the thread is non-standard) and follow the simple instructions for pairing and setup.

Pros:
Endless per room automated control if desired.
Once you have the system set up to your liking you just forget about it and let it do its job; you don't even need to touch it if you go away (location based control).
Location based control. Easy override of control manually or using mobile phone app anywhere you have signal/wifi.
Auto frost protection.
Reasonably good integration with Alexa/google/IFTTT, etc.
Auto "open window" detection - shuts off heating to room if it detects open window/outside door - reasonably reliable...
Intelligent room heating - heating does not overshoot (at least not very much); it allegedly "learns" a rooms thermal characteristics and adjusts for outside temperature to integrate heating curves.

Cons:
Needs interweb though it can easily be controlled manually if the web is down.
Batteries in thermostats last about a year and the system emails you when a battery is running low - replacement is easy; I bought cheap job lots of batteries on amazon.
Setup can be expensive if you are doing a whole (large) house (I got the basic started kit on a special offer for £125 at the time, the upstairs zone thermostat for another £100 and then each radiator for ~£60). I reckon it will pay for itself in about 2-3 years. (OvO is currently offering 20% off on Tado, apparently)
Unlike Nest, it does not "learn" your movements and setting; you manually set room/house programs to what you want and change them whenever you like (which I prefer).
Webb app not quite as nice as the phone app.

I am still waiting for Tado to implement a separate hot water control similar to their air conditioning control; our house with 2 separate pumped zones is just a little too "complicated" to allow hot water as well; I may get around to hacking a ciustom solution sometime....

ian

  • fatuously disingenuous
    • The Suburban Survival Guide
Re: Central heating thermostat
« Reply #9 on: October 22, 2018, 01:06:38 pm »
Our dumb Honeywell makes an extended tctctcttcccttttccctttcccctttccccttttcctttttcttttcccctttttccccttt noise when turning on or off sometimes. I assume something vibrates inside. Flicking it seems to work. Possibly it runs off agitated moths. That's my working theory at the moment. Temperature-sensing moths. They seem to work though. Setting it to eighteen degrees seems to consistently result in a house of 21-22 degrees.

I do keep meaning to get one of those internet-of-things things. To be honest, the dumb one mostly works fine, it's in the hallway so not exposed to the vagueries of drafts and open doors. Through careful tweaking of thermostatic valves, the house warms evenly, by setting everything low upstairs, the heat rising up the stairwell balances out. As we never close doors (because cats) everything just works. I'm not convinced of the benefits of further sophistication and zones now everything is in balance. There's no point heating a single room if you can't close the door. We used to have zones and stuff in the last house, never really bothered, all the heat went up the big three-story central stairwell.

That said, it would be nice sometimes to turn it on and off remotely. An off-button for cats would also be helpful.
!nataS pihsroW

Re: Central heating thermostat
« Reply #10 on: October 22, 2018, 06:15:46 pm »
The Honeywell Evohome system works well. Possibly a bit more expensive than others. It has an internet connection, but it works fine without it, and it does all the timed settings, holiday periods etc without it. Each radiator valve runs on two AA batteries and seems to last over a year, and then gives a warning on the control panel.
Quote from: Kim
Paging Diver300.  Diver300 to the GSM Trimphone, please...

velosam

  • '.....you used to be an apple on a stick.'
Re: Central heating thermostat
« Reply #11 on: October 22, 2018, 06:34:39 pm »
Mine is a Drayton Room Stat and its connected to a glow worm blower, both close to be antiques.

I may have to change the boiler next year, so I don't its not worth me spending loads if I am going to have to upgrade the whole system. Also two of the rooms have relatively low usage (kids bedrooms) so it kind of makes sense to have something where I can set alternative temps.

The thermostat is in the very small hallway so subject to the influences of an opening and closing door.

Given its mains voltage will it have a particular fuse or do I have to switch off all the electrics in the house?

I could not see a particular fuse for it

Kim

  • Timelord
Re: Central heating thermostat
« Reply #12 on: October 22, 2018, 06:43:29 pm »
Central heating is usually powered by a fused spur (or 13A plug-inna-socket acting as a lazy plumber's double-pole isolator) from the sockets ring main, normally by the boiler or in the airing cupboard.
To ride the Windcheetah, first, you must embrace the cantilever...

Mrs Pingu

  • Who ate all the pies? Me
    • Twitter
Re: Central heating thermostat
« Reply #13 on: October 22, 2018, 08:27:37 pm »
I got an Amazon Echo last week. Great device.
I have a radio controlled thermostat. The control box is on the wall beside the boiler.
Any ide how wassy/hard it is to replace the thermostat with an Amazon compatible one?
And what brand?  Nest looks nice. Or Hive?
Bad stories welcomed as are good.

Yes they are spendy, compared to "dumb" 'stats, but ours saved us ~£1000 in it's first year of use (3 adults (near enough) and a cat in 3 bed detached)

Holy moly, was your boiler running on tenners?

Thread hijack:
Can someone explain to me how having certain rooms unheated/lower T makes the heating more efficient? Surely if you're only heating one room the boiler is still being run to heat that room? Or is it to do with the fact that the water is at higher T when it returns to the boiler without all the other radiators on sucking it cold?
Do not clench. It only makes it worse.

Feanor

  • It's mostly downhill from here.
Re: Central heating thermostat
« Reply #14 on: October 22, 2018, 08:49:09 pm »
Yes, that's pretty much it.
There are various thermostatic devices in a typical heating system.

Room Stat: Usually in the hallway, not a useful place. Will usually be Calling for Heat, because even if the rooms are warm, the hall may not be.
TRVs: Since the room stat is pretty much always On, the room TRVs are probably what's actually controlling the heat output.
Boiler stat: Once the room TRVs shut down and the return is coming from the bypass loop ( eg the towel rail ), then the boiler will shut down when that's also hot.

So yes, once the return temperature is indicating that none of the radiators is dumping heat, then the boiler will cycle off.


ian

  • fatuously disingenuous
    • The Suburban Survival Guide
Re: Central heating thermostat
« Reply #15 on: October 22, 2018, 09:07:24 pm »
Hmm, I'm also not convinced overall that if you're heating the house to a desirable temperature and everything is balanced and nowhere is too hot, there's much more to be done with the heating – money is probably better spent on keeping the heat in. I suppose some the heat goes up the flue when the boiler is running.

I've no idea what efficient is, we're waiting for our boiler to die, which is refuses to do. Ancient Gloworm thing. Loath to replace it while it still seems to work perfectly. Our combined electricity and gas for a winter quarter is about £300-350 for a four-bed detached house, though admittedly we only run the heating in the morning and evening. I run a oil-filled radiator in my remote command centre during the day rather than heat the entire house. There's obviously a blip in winter when the in-laws turn up for Chrismas and turn the thermostat to Bahrain.
!nataS pihsroW

Mrs Pingu

  • Who ate all the pies? Me
    • Twitter
Re: Central heating thermostat
« Reply #16 on: October 22, 2018, 09:18:03 pm »
Ta. I'm not convinced it would be worth a smart/zoned/etc system with a grand total of 5 radiators. I only finally got round to hanging up the wireless stat last week. It used to live in the lounge til we got the furnace stove installed whereupon I relocated it to the bedroom. I don't think it was really designed to be sat on a chest of drawers.
I do like the idea of the weather/thermal mass compensator though. Not that I'm doing anything until the boiler decides to go on the fritz regularly - I'm not convinced the energy efficiency benefits would outweigh the cost to the environment of building a new boiler for our meagre abode.
Do not clench. It only makes it worse.

Re: Central heating thermostat
« Reply #17 on: October 22, 2018, 09:20:33 pm »
+1 for tado.  Very easy to install and setup.  The geo-fencing works really well,  it detects when there's no one in and turns the temperature down and switches the hot water off.  As energy bills rise smart heating systems can pay back very quickly.
Keep it real

Adam

  • It'll soon be summer
    • Charity ride Durness to Dover 18-25th June 2011
Re: Central heating thermostat
« Reply #18 on: October 22, 2018, 09:28:28 pm »
I have just bought a house. Turns out that the central heating thermostat only kicks in at 25C!

Is it an easy change to a new one, and any recommendations of what to buy and how to change the whole unit?

thanks

sam

It may be simpler to keep the existing one, if it's one with an actual dial, rather than electronic.  You can lift it off the spindle, turn it clockwise a bit, so that the temperature it shows when it clicks on it is more in line with the current temperature.
“Life is like riding a bicycle. To keep your balance you must keep moving.” -Albert Einstein

Kim

  • Timelord
Re: Central heating thermostat
« Reply #19 on: October 22, 2018, 09:49:11 pm »
The main win I've found with smart heating control is that it automagically adapts according to whether we're upstairs, downstairs, or not in.  And as it knows when we're in bed and when the alarm (if any) is set for, it does the right thing there, too.  I'm sure it saves some fuel (we've not had a dumb system since we moved into this house), but the primary benefit is improved comfort.  There's a lot to be said to being able to push a button to boost the heating while you're in bed, or as your train arrives at Mordor.

Whether a simple timer could achieve the same thing depends on how consistent your habits are, and how big a natural temperature difference between rooms you have to fight.
To ride the Windcheetah, first, you must embrace the cantilever...

tonycollinet

  • No Longer a western province of Númenor
Re: Central heating thermostat
« Reply #20 on: October 22, 2018, 10:30:38 pm »

Yes they are spendy, compared to "dumb" 'stats, but ours saved us ~£1000 in it's first year of use....

Holy hell - what is your normal bill? We only pay a little more than you've *saved* for gas AND leccy.

hellymedic

  • Just do it!
Re: Central heating thermostat
« Reply #21 on: October 22, 2018, 11:17:35 pm »
My new boiler came with a complicated RF battery-powered thermostat.
My summer gas bill dropped a bit, presumably due to lack of hot water cylinder, but winter bills were much the same.

MikeFromLFE

  • Previously known as Millimole
Re: Central heating thermostat
« Reply #22 on: October 23, 2018, 08:46:31 am »
We went with a Conrad EQ3 control system, which gives us room level programs, but wasn't as expensive as a full blown nest/tado system which is what I really wanted.
Each room is fully programmable, and there's a hall 'call for heat' thermostat.
Conrad do an Internet connected device that works with the EQ3 system, but it seemed archaic, and the translation of the instructions from the German was iffy.
We've definitely seen an improvement in comfort levels, but savings are hard to pin down because we have changed the boiler too.
(The radiator TRVs for the EQ3 system are also sold by Pegler, but they are not compatible with the EQ3 controllers DAHIKT)
Too many angry people - breathe & relax.

ian

  • fatuously disingenuous
    • The Suburban Survival Guide
Re: Central heating thermostat
« Reply #23 on: October 23, 2018, 09:32:52 am »
Hmm, I'm still unconvinced that some of these systems aren't a bit overengineered unless you live in a mansion or stately home, perhaps a palace, or maybe a castle. I'd deffo get one if I lived in a castle. Well, after getting a moat, of course. And a drawbridge. I think ravens too. And sharks for the moat. But then I'd get mega-zonal thermostaticalators. They'd be right up there near the top of the list. Oh, maidens too. In turrets. Comfortably warm turrets. I'd probably have to heat the moat too, for the sharks.

I was never convinced the one we had in our last place wasn't an excuse for buttons and contrary controls. Press and hold. PRESS AND HOLD DAMMIT! I think I set some temperatures than got bored. All the heat got sucked up the big central stairwell anyway. I don't think the radiators on the top floor ever came on.

(Anyway, to prove that my household appliances read this forum, the (probably needing replacing) CO alarm in the boiler cupboard went off at 6.40am. A delightful way to be awakened. It didn't trip any of the others or go off again, and I'm not dead. Leastways, I think I'm not.)
!nataS pihsroW

Re: Central heating thermostat
« Reply #24 on: October 23, 2018, 06:24:03 pm »
Our house was built in four phases. There are 11 radiators in 9 rooms and the kitchen has underfloor heating. There is a wood-burning stove in the lounge.

There is no way that one thermostat could measure a representative temperature. Fixed thermostatic valves can limit overheating but don't respond that well, and they can't wind up and down for different times of day. Also having electronic valves in each room means that the boiler never runs unless needed, so we are very happy with our choice.
Quote from: Kim
Paging Diver300.  Diver300 to the GSM Trimphone, please...