Ideal Classic RS 50 problem

11 Jan 2009
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United Kingdom

I have an Ideal Classic RS50 central heating boiler that is driving me slightly mad. This problem started a couple of months back but yesterday took a turn for the worse.

What happens is that even with the programmer set to constant and with the room stat turned right up, the boiler will only fire up for a couple of minutes and will then stop running, almost as if there were no call for heat from the thermostat. It will then randomly fire up again for a few minutes a while later and this just goes on and on.

The pilot remains lit and stable at all times and the boiler seems to decide for itself when it wants to run or not run. I have checked that the pump is running ok and it does seem to circulate the hot water on the rare occasion that the boiler runs, I just cant seem to get the boiler to run as it should. The boiler itself is turned up to max too.

Does anyone have any ideas where I should start? I can try shorting the room stat just to rule that out, but am I potentially looking at a problem with the gas valve?

Thanks in advance,

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If pump definetly carries on runnin then the motorised valve and roo stat are ok .
When it does it turn the boiler stat up and down if you can hear a click and nothing happens then it is the gas valve solenoid .
Check by using multimeter there should be 240 at gas valve if everything is demanding heat
Thanks namsag

The pump only runs when the boiler is running - would this suggest that the fault lies with the stat? Is it the room stat that switches the pump or is it controlled by the boiler itself? I guess if the stat switches both then that would indicate that the stat may be at fault?

Btw - the boiler is CH only - hot water is provided via an immersion heater so presumably there is no motorised valve in the system?

I'll go and whip out the multimeter now and see what's going on.


The way it should be wired then is live out of clock to room stat then out of room stat then split so pump a boiler come on together ,
If they both dont come on then fault is roomstat or clock
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I've just picked up a new stat as I think the old one has gad it, but wanted to check something about the wiring:

The old stat (Sopac TA 650.03) had 3 wires connected, one being an earth, the other 2 being a yellow cable connected to terminal 1 and a red connected to terminal 3.

The new stat (Drayton RTS 1) states in the instructions that a neutral connection must be made to terminal N, presumably because it is an electronic unit rather than a mechanical switch, the old unit had no neutral connection as it is electromechanical. The other 2 connections I'm happy with.

Should I just connect the unused blue wire that was tucked away behind the old stat or do I need a different stat?

Many thanks,

To be honest the drayton is a sh#te stat and very in accurate so even if the neutral could be connected at both ends its not going to be that good. best change it for a honeywell then its just back into same connections
Yes the blue wire should be the neutral you require, but check it is connected properly at the other end first.

I would assume this stat requires the neutral for the anticipator to work, that makes the temp switcing more accurate.
Has it been serviced recently,a sooted heat exchanger would cause this problem?

RS50 Pilot remains lit at all times so that would suggest permenant pilot model so there would be no sparking
Its just a thought I have - pilot can be perm lit, but its continously sparking at SG1 and main gas valve not opening

Pilot CAN be lit whilst sparking is going on...

Sorry - me thinks this post was meant for another problem I was looking at lol - sorry!!
OK, I've got a theory but I may be talking out of my...

With the room stat turned right up and the programmer on constant I have checked for a live after both and have found there to be a live feed to the boiler and the pump but the boiler will still only run for a few minutes every now and again - the pump though seems to be only running intermittently even when the boiler is running.

So my theory is this:

Is there some kind of over-temperature sensor in the boiler cutting it out because the pump isn't circulating the water? The pump body is extremely hot but the pump appears not to be working. You can hear some feint but detectable noise from the pump when changing between the speed settings but the pump doesn't seem to spin.

Is the boiler cutting out because the water inside it is too hot and only running again when the temperature drops or the pump tkicks in briefly?


Nothing wrong with the boiler. This is a very simple boiler that controls nothing but itself.

Sounds more like you need a new pump, or at least check the system is full of water, the f&e tank is full and all the rads are bled.

The boiler is reaching temp too quickly and the stat is turning it off, as it should do. It is taking ages for the boiler to cool down because there is no flow through it, due to the dodgy pump.
You reckon pump could have airlock behind it?? like cavitation possibly??
Pump should be hot, but it being red hot would point to insufficient circulation - ie boiler is reaching temp rapidly - now I wonder what resistance ya getting across stat cos low resistance points to high temp - have temp diffs been done on boiler do ya know?

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