Replace analog timer?

[Welshgasman]

Hi all,
Looking for some advice please?

I have an old Ideal Concord WRS boiler circa 1979. Not sure if is a 230A/240A/255A. I am also not sure if it is gravity fed or fully pumped. There is a small pump to the right of the boiler
It has the programmer in the attached picture. Google Lens showed this as a Landis & Gyr RWB2, but looking for that on the net I see very different interfaces?
In looking for a replacment I found the Siemens RWB29SI?

In several threads on here, it is mentioned that the backplate is the same and that it is a straight swap. Siemens themselves state that. However in mine all the wires appear to go in vertically to the right side of the unit as you look at it's face.

Now I am not sure mine is indeed an RWB2, how hard would it be to replace this old timer please.
I do not intend to do it myself more than likely, but have a friend who could fashion some sort of mounting plate for the new programmer, then get an electrician in.
The current one is bolted to the boiler front panel with two screws.

Thank you

Edit: I now believe it to be gravity fed, as I do not have any controlled valves around the hot water tank.

 

[CountryFan]

I doubt that's a universal backplate being part of the boiler. It would probably be better a new one and new/altered wiring at the boiler.

 

[ericmark]

I note either central heating and hot water or only hot water, which points to a C Plan. There is no option for central heating only.

Back when CFL lights first came out, I realised there was a problem. With tungsten lamps the inferred from the lamp resulted in the evening when one was just sitting you still felt comfortable as one was getting this inferred, as they were replaced, we well at least I wanted the room warmer in the evening to during the day, so I wanted a programmable thermostat.

Combining the timer function and thermostatic function into one device, needed so alteration in the wiring, Nest Gen 3 allowed in with N/O contacts and out from the com contact, and Hive had a special configuration for C Plan with one set of contacts for the pump and another for the boiler.

However, I am jumping ahead, step one is to decide if you want DHW heated by the boiler in summer?

What we have to consider, is the cost to fire up the boiler before it heats even one pint of domestic hot water, in the winter heating DHW when boiler also heating radiators is generally good, but in summer, often the immersion heater is as cheap or cheaper to run to the gas or oil boiler, even when gas is cheaper than electric, so much energy wasted each time the boiler turns off/on.

So next is to look at 5 to 10 years time, as TRV heads can be added latter, but you likely want a thermostat/hub or thermostat and hub that will accept TRV heads to be added later.

I like the Wiser system, but it will not work direct with C plan, where the Hive will, so although I have C Plan in summer I heat DHW with solar, or off-peak, not with my oil boiler. But oil boiler does heat it in winter.

So your looking at the future as much as now, and allowing for changes in the future to make it better.

Distance boiler to cylinder makes a difference, in my case boiler two floors below the cylinder, so there is a lot of pipework to heat.

I found to use oil to heat DHW in the summer needed 5 times the energy to heat it with electric, since electric was 5 times the price of oil, sadly no longer the case, but it would have worked out even in summer using oil or electric, and once I had off-peak and solar, much cheaper to use electric.

Next is the timer where you would want to measure temperature, some systems the programmable thermostat and hub are the same item, others the hub and the thermostat are separate items connected together wireless. Can't really advise on a system without knowing if both can be combined or not.

I am not saying spend a fortune now on the best smart system, what I am saying is select one which you can if you wish expand on.

 

[Welshgasman]

I doubt that's a universal backplate being part of the boiler. It would probably be better a new one and new/altered wiring at the boiler.

No, it is not. Researching more, they are talking about a small backplate, nothing like what I have.
I am thinking of a control box mounted somewhere and the backplate fitted to that.
I have just bought the Siemens RWB29si as a start.

With all of this, do I need an Electician or a Gas Engineer?

 

[Welshgasman]

@ericmark

The boiler is 47 years old. Still working fine. I am retired and on a small MN pension and State pension, so have to watch my pennies.
Right now, I am just looking to replace the programmer. Leave everything else as it is. If and when the boiler goes, I will then explore more automatic measures. My hot water tank is upstairs in a 3 bedroom house.
The boiler is hidden behind a kicthen cupboard door, so the installation doe snot have to be pretty, just functional.

Ironically since I have started looking for a replacement, it is behaving itself, and moving in correct increments.

 

[CountryFan]

With all of this, do I need an Electician or a Gas Engineer?

Either, but you need to tell them exactly what you have and what wants doing as not all of both trades are competent to do this type of work.

 

[ericmark]

So easy bit first, L to L and N to N.
L1 to 4
L3 to 3
But then it gets a bit harder, the existing timer has the option to change what it does. They were sold as 10/16 programmable controllers, and they counted off as an option, but the internal switches changed it from 10 to 16, and it depended on if the system allowed central heating without DHW, many did not.

The old controller for C Plan is now hard to find, I used Nest the plan is not given in the standard instructions, but it can be done as the Com is not linked to the line in, but with the controller you have selected it is linked.
Hive allows an internal configuration but the C plan came with three variations The simple one does not allow any temperature control of DHW it is same temperature as the central heating water, and in summer one had to take a guess as to how long it needs to run for, I found around ½ hour a day was about right. The second allows you to use a tank thermostat in the summer, winter it is same as central heating water, but summer you can control DHW temperture, and third not often found, you can control DHW temperture summer and winter.

The point was, the thermosyphon allows the boiler to cool by heating the DHW with the motorised valve that was no longer true. So we got the Y Plan with three port valve, which did allow the boiler to cool by heating the DHW.

This does have a few anomalies but does seem to work in general better, but as boilers improved we went to the S Plan job one is to work out which plan yours is working on. The C and Y Plans are not used much today, only old oil boilers tend to use them, oil boilers last longer. But to find someone here in Wales, easy, but across the border into England to find someone who knows the old system is harder.

 

[Welshgasman]

Wow, thank you.
That will take a while to understand.
My existing system allows Water Only, Off and Water and Heating. I cannot have Heating without Water and I am fine with that.
I believe I must be on the C plan, as I cannot find any motorised valves near my hot water tank. I would certainly be on the cheapest option, having known the builder.
Luckily I am in Wales, and my previous bosses who buy/sell/rent houses have a lot of contractors at hand and I have already asked them for a Gas Engineer. I did originally ask for an electrician, but the one they offered, did not want to touch it after seeing a picture of the programmer.

There is also a power supply to the igniter. Is that going to cause any issues with this Siemens RWB29si ?

I also took note of your opinion to use the immersion heater in summer, instead of the boiler. Something I have not done for years, thinking the gas version was the cheapest. In summer, the boiler is on about 1 hour, twice a day. That is as small a time as I can manage, with both red & blue lugs adjacent to each other.

 

[ericmark]

In summer, the boiler is on about 1 hour, twice a day. That is as small a time as I can manage, with both red & blue lugs adjacent to each other.

I had the same, swapped it for Nest at ½ hour per day seemed too much, at ½ hour 4 days of the week warm water not hot, the boiler is 20 kW so at ½ hour per day it only actually runs for 20 minutes, as return water too hot, so that's 186 kWh per lunar month. My solar diverter (iboost+) measured how much electric used per month, at 34.64 kWh for 28 days. So it uses just over 5 times as much, and I pay 8.625p/kWh overnight, and loose 12p/kWh if I use it during the day in lost revenue from the solar, so for me no question cheaper to use electric. But at 24p/kWh for electric, gas would need to cost less than 5p/kWh to break even, seems unlikely it will be that cheap.

Running the boiler for a whole hour per day, an immersion heater will be cheaper.

You can see where I live, am I anywhere near to you?