Dear all,

I have recently purchased a house and hesitant to change a working boiler just because it is too old. I instead want to upgrade the timer/programmer switch. The house came with a Hideaway GlowWorm Boiler coupled with a Drayton SM2 programmer switch (Both Pics attached). There is also a thermostat in the hallway - not sure if this works or not though.

Could you please suggest whether I can upgrade this programmer switch to a latest and Smart wifi enabled one? If yes, could you please suggest which one to go for? If no, what is the nearest one I can upgrade to?

Thanks in advance.

A programmer / timer such as you have is just an electromechanical switch, so yes you can change it to a "new fangled one" it would be your choice of which one you want to (waste) spend your money on, and obviously you have to get BB first.

_________________
Fret not, a forum is a collection of opinions. Above, are mine.

Which is correct? Metre or Meter? Click the link to find out more.

Working on anything electrical? have you got a multi meter? why not? Would you hit a nail with a shoe?

If gloom had a voice, it would be me.

How to post a picture on this forum Click here

I have to agree with "someone-else" so easy to waste money with wifi enabled. However it does seem to go in stages, so from out set you need to work out what stage you want, as next stage often means replacing it all over again.

So I will try to explain, I don't think your boiler has the option for a thermostat which connects to the boiler bus, not even sure if that boiler is a modulating boiler to start with, I think it is simply on or off? Also not sure if mains voltage control or 24 volt, this will make a difference, if 24 volt then you need volt free contacts for the controller, which knocks out Hive, but think Nest is volt free.

However the modern system uses the thermostatic radiator valve (TRV) to control, and when using these you have a by-pass valve so when they all closed there is still some where for water to go, before the TRV often there was no by-pass valve.

To use the same boiler for domestic hot water and central heating we had plans, refereed to as Y plan, C plan, W plan to name some, and some of the old installations had no way to turn off domestic hot water and leave central heating running, and even when there was, it was some times hit and miss where it simply turned off pump to get domestic hot water only.

The programmer you show often had a mechanical lock, to change from 10 to 16 programs, this was all down to if you could turn off the domestic hot water.

It was common to use the timer you show to limit domestic hot water temperature by turning on just twice a day, and central heating was often just a back ground heat, and the occupants would use other fires to heat rooms in use.

Before altering control, you need to work out what you already have? In my old house I fitted TRV upstairs only to stop bedrooms getting too hot, I fitted a second boiler for domestic hot water so I did not require a hot water tank, and converted that space into a bedroom. I would not do that today as now we have combo boilers.

However step one is likely to set heating on 24/7 on the programmer and swap the thermostat for a programmable thermostat which would likely cost around £35 and means instead of off/on at set times, it sets different temperatures at set times, typically today 6 different temperatures through the day. But that will not work if you can't control domestic hot water, it may require a motorised valve fitting and a tank thermostat to turn off domestic hot water.

Hysteresis i.e. the difference between when heating switches on to when it switches off and the amount the room temperature varies is the main reason for an expensive thermostat. So I will talk about three thermostats, the Honeywell Y6630D wireless has built in anti hysteresis software, what it does is start switching off/on before the target temperature so the heating does not over shoot, it also fails safe, i.e. if battery becomes flat, it switches off, it will not stick in on mode. The Flomasta 22199SX hard wired has six times so you can program it, but no anti-hysteresis software, the difference on/off is 0.5 deg C so better than mechanical but not as good at maintaining temperature to the Honeywell Y6630D but allows you to program (This is used in my old house very satisfied with it) the Horstmann HRFS1 seems really good, programmable loads of options, wireless, however it does not fail safe, I returned to mother's house to find it at 28 degs C when it failed to turn heating off, so in spite of good specification, I would not recommend.

So hard wired not reason not to use cheap Flomasta 22199SX but if you go wireless then you need the more expensive.

Into the wifi enabled, EvoHome would normally be what I would go for, it uses the wifi TRV heads to control 6 rooms independently, however in your case I hesitate, as not sure if you can easy fit TRV's without also fitting by-pass valve, and not sure how well it would work with non modulating boiler, as to Hive it does not have volt free contacts for the duel control model which you would need, so not sure if it could be fitted, Nest is very good, and it has volt free contacts and it can talk to MiHome electronic TRV heads so can expand, but getting the 5 volt supply to thermostat is not easy. So I would spend £35 on the Flomasta 22199SX and see if that is enough, it's easy to fit, you just turn programmer on 24/7 and let the thermostat do the times.

When you replace boiler, then decide which control system. With a new boiler it will be modulating, i.e. not fixed output, and if OpenTherm enabled you could use something like EvoHome, there are others, to adjust the boilers output, since they don't turn off/on there is no hysteresis so one can see the point in expensive controls which retain this ability to vary output, I think most wifi thermostats are able to be used to modulate rather than turn boiler off/on, the exception is Hive, why anyone fits Hive I don't know. However if your not changing boiler, and if the control is 230 volt then Hive is for you likely the cheapest option with wifi and would actually likely suit your needs, but if you do change boiler, then likely Hive goes in bin, so is it worth spending that much on an old system?

Be aware if you do change boiler, some makes only allow you to use their own modulating thermostat, others use OpenTherm so you have a whole range to select from, personally any boiler without OpenTherm I would reject. I have Bosch and they use their own Wave thermostat and it only works in one room, what's the point of that?

As a foot note, normal way to control boiler is from the motorised valve, not direct from thermostat so thermostats open valve, then once valve open it starts boiler, since motorised valves are either open or closed, any house where the home is split into zones, can only use on/off thermostats, so can't use the modulating output of boiler to the full. This is the big problem, new houses have in the main two zones which instead of improving control does the reverse, some government official has thought Oh that's a good idea, but had no idea how modern boilers work.

@ericmark, great! Thank you very much for taking the time and providing your valuable input. I have learned something new today but I still do not know the technicalities i.e. whether or not it has a by-pass valve, whether a termostat can be used and etc.. So I am going to get boiler people to check and advice which programmer suits best.

I bought TRVs last week to get them fitted on all of my 7 radiators around the house, to which my builder agreed to drain the boiler and fit them tomorrow. But now, I will need to stop this and find out whether or not the boiler has a by-pass valve to handle these!

After such an informative reply from you I thought I'll go find the boiler model and opened its front door. I can tell you that it is mains driven (see attached pictures) but couldn't find the model number.

When it comes to hot water, it can be turned on independently but it also turns on when central heating is turned on, so I can't have central heating on its own.

I intend to change the boiler when I get my kitchen re-fitted. Not sure when this is going to be though.

I am okay with either a wired or wireless thermostat/programmer but I am looking for something better than the existing one.

In my previous rented accommodation, we had worcester boiler with wireless thermostat. As you mentioned, we used to have it 24x7 and was temperature + time conrolled. With such experience, this one in the new place isn't exciting :)

These were the TRVs that I bought

https://www.toolstation.com/corgi-angled-trv-lockshield/p38201

If you leave one radiator without a TRV and of course don't turn it off you are likely OK without the by-pass, normally the towel rail has no TRV to get around the problem with no by-pass valve.

Please I am an electrician not a heating engineer, however so often we are asked to do daft things like fitting programmers and thermostats in the wrong place or wrong system, I have realised I need to know how they work, even if I don't play with it, but need to know when to say no I will not do that as it will not work.

In the main we are told thermostat is faulty rooms are not getting hot after a thermostat is fitted, and find no one has ever set the lock shield valves. Lost count of how many times I have had to do a rough setting to get heating working.

Hi ericmark, Thank you. I now got my TRVs installed! :). Left out the towel rail in the bath and the radiator in the toilet. All looking good at the moment :)