Programmer / Timer replacement on an old boiler . Pump over run needed

[Mat29a]

In that case, as it is just a connector for the two wires and there is no other connection inside the existing timeswitch, then you could wire in your new timeswitch as below, leaving the old timeswitch, and all of other existing wires, including its 230v supply in place exactly as they are. That way, the rest of the circuit doesn't change, and the pump overrun mechanism & microswitch will remain exactly as it is. You would just be changing the timer part of the circuit.

The new timer would have to be mounted on the wall at the side of the boiler rather than inside it, and whilst the old timer physically remains in place, it won't have any time control of the boiler anymore.

View attachment 140312

The conversion kit would of course, be a better long term proposition.

Thats what I am doing right now ... keeping the old timer as is. the boiler L & N redirected to new boiler + mains supply L & N
shared between the 2. using the old as pump over run. new timer just to serve the boiler.
Mounting new timer externally is much better and very convenient.
the new 424 emerald timer is very good. no pcb , no chips/electronics, & nothing to burn out/break down in a hurry.


I was fancying re-building the pump overrun sometime. i like the very simplistic design.
As I already have a couple of spare burgess microswitches ( only couple of £ ea).
Building of the enclosure to exact fitting is not an issue. and I can reuse the stat plate which is still perfect.
then mount the entire tiny unit in boiler housing old timer area... and discard old timer. cost will be next to nothing.
All i need is to find out where ( if possible ) to buy that only stumbling block, the conductive ceramic piece. although it still works well.
It will be a long shot. but as long as everything is working , I can keep searching.

the converter is a good solution.

 

[Mat29a]

using existing configuration with new timer
will be installed after next visit to shops to grab some crimp connectors

 

[heatservice]

Just a suggestion, why not use an electronic programmer and future proof it, besides the fact their probably cheaper they also have features like 1 hour plus etc and you will be able to properly update you system with a 3 way valve with room & Cylinder stats in the future, you must be realistic your boiler isn't going to last forever and some small component could render it obsolete if its not available.

 

[Mat29a]

Just a suggestion, why not use an electronic programmer and future proof it, besides the fact their probably cheaper they also have features like 1 hour plus etc and you will be able to properly update you system with a 3 way valve with room & Cylinder stats in the future, you must be realistic your boiler isn't going to last forever and some small component could render it obsolete if its not available.

Thanks to all - my current issue is resolved for now .. ( but still exploring .. )
Heatservice as you were the first to kindly mention Pipe stat what is your ( or anyone's ) opinion on this (ebay)
interesting stat... it claims good for 10-90deg C
(As this is a cylinder stat I am puzzling how to wrap it around a 22mm boiler-out pipe to get the conduction, so it can pick up the heat ?)

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Please correct me
For pump overrun application , this can be connected independently from timer or boiler wiring:
Permantent Live to C(common) - the out from 2 to pump ( 1 is unused )
Neutral to pump

( ignoring the accuracy of the stat for now ) I assume C switch is the cold position
When temperature reaches set level (say 40C) the switch drops from C to 2
and powers the pump. When Boiler is off and temperature drops below 40C
stat back to C and 2 ( pump) is disconnected ..

 

[heatservice]

Best to use a pipe stat as its backplate which makes contact with the pipe to register the temp is curved or angled unlike the cylinder stat which is flat.

 

[Mat29a]

Best to use a pipe stat as its backplate which makes contact with the pipe to register the temp is curved or angled unlike the cylinder stat which is flat.

Got it .. thanks !!

 

[Mat29a]

found this interesting image of pump overrun solution? with Honeywell pipe stat

 

[Mat29a]

All cylinder thermostats are pretty much the same, and will have the necessary changeover contact. The Honeywell L641B you quoted earlier would be OK, but if you do use that, get the 1012 version of it that will allow you to select the 60 degrees C, setting heatservice suggests. The version of it you posted earlier is the frost protection version 1004 and doesn't go that high.

Interestingly the pipe thermostat wiring diagram I posted earlier and your diagram of the "Burgess Switch" work in exactly the same way using a changeover contact to switch the pump between the 'boiler switched live' and a 'permanent live'. The only difference is that the microswitch has its own heating device that heats up with the boiler. The pipe thermostat uses a hot pipe heated by the boiler instead. The pipe thermostat should be fitted to the flow pipe just as it leaves the boiler.

Stem: I quite favour your suggestion of Honeywell 641B 1012 pipe stat. not now, but only when the old timer microswitch gives up.
Just connect the pipe stat to the pump totally independently, controlled by the boiler out temperature.
with the Timer just controlling the boiler alone. was that what you meant all along ? ( I did say Im very slow LOL )
Do you know what size pipe it fits?
thanks

 

[stem]

Pipe stats have various uses. The one in your photo could be there to provide a pump overrun, but they are more commonly used for frost protection in conjunction with a frost thermostat. The frost stat senses a danger that freezing temperatures are approaching, and turns on the heating overriding all other controls. The frost stat is wired in series with a pipe stat to switch the boiler off once the pipes have got warm enough to alleviate the risk of them freezing. The location of it would give a clue, but without seeing the rest of the system and knowing if the pump is on the flow or return, it's difficult to tell. If it was part of a frost protection system it would be located on the 'return' pipe close to the boiler. For a pump overrun it would be on the 'flow' pipe just after it leaves the boiler.

Below is how I believe the microswitch is wired now, although you should check that all three of the wires are connected internally as I've shown. For example that the pump is connected to the common terminal and not the normally open or normally closed etc., If there is not a schematic diagram printed on it, then it will have to be checked with a multimeter, (or opened up if you wait until it's broken). If my assumptions are correct then the corresponding connections for the Honeywell pipe thermostst are shown below also.



Pipe thermostats are very versatile and will easily fit boiler flow and return pipes whether 28mm or 22mm. They are quite slim and have a metal back, this back must be held tightly against the pipe to sense the surface temperature, and springs or straps are provided to hold it in place. You can see the pipe stat parts below and if you look carefully in the photo you have posted, you can see the springs holding it around the pipe.

 

[Mat29a]

Below is how I believe the microswitch is wired now, although you should check that all three of the wires are connected internally as I've shown. For example that the pump is connected to the common terminal and not the normally open or normally closed etc., If there is not a schematic diagram printed on it, then it will have to be checked with a multimeter, (or opened up if you wait until it's broken). If my assumptions are correct then the corresponding connections for the Honeywell pipe thermostst are shown below also.

View attachment 140372

your microswitch overrun diagram is spot on.
the unit is a clever microswitch adaptation with parts not exceeding a few quid to manufacture.

Pipe thermostats are very versatile and will easily fit boiler flow and return pipes whether 28mm or 22mm. They are quite slim and have a metal back, this back must be held tightly against the pipe to sense the surface temperature, and springs or straps are provided to hold it in place. You can see the pipe stat parts below and if you look carefully in the photo you have posted, you can see the springs holding it around the pipe.

I agree with the versatility, hence i quite favour this method . (good to know the 1012 can fit diff. pipe sizes)
thanks!!

 

[stem]

Stem: I quite favour your suggestion of Honeywell 641B 1012 pipe stat.

Err....actually, it wasn't my idea.

You could have the pump wired via a pipe thermostat attached to the flow so it would continue to run on until temperature dropped.

But I like it

 

[Mat29a]

Opps, big thanks of course to heatservice. but thank you all the same .. this has been a very interesting & educational discussion. it has helped me understand more by focusing on the principles, and I was able to resolve the pump overrun by using the existing old timer with new timer, I wouldnt have otherwise. But when the old microswitch overrun dies, it will be the pipe stat. I hope it will also benefit those are interested or like to learn something about stats applications, and overrun relay etc ..

 

[heatservice]

Ive enjoyed this exercise in problem solving a real team effort, 30 years ago + I did alot of this kind of stuff so it was good to find the grey cells are still working lol

 

[Mat29a]

Ive enjoyed this exercise in problem solving a real team effort, 30 years ago + I did alot of this kind of stuff so it was good to find the grey cells are still working lol

lol ... it shows that your grey matter is in good nick heatservice. I guess once it becomes 2nd nature, it will stay indefinitely ...
it's always good fun to solve problems or work around them. when it works it feels good.
Then move on to the next, whatever it may be, but only quite a safe one.
I am looking for the next small project ....

 

[Mat29a]

thanks