Control logic with 2 rad circuits, ufh, dhw and towel rails circuits

[taffyinhighlands]

I have an oil heated circuit that now appears to be misbehaving and the main circulation pump running across the bypass wgen all the logic controllers are off.
I think this is a new phenomena but cant be 100% sure.
The ufh isnt on a logic controller, and its own booster pump is triggered by the room thermostats.
The wiring is a bit of a mess with limited labelling, and so its not clear how or if the ufh triggers the boiler, or if the pump is on the same circuit as the boiler.
I've tried to get someone local to come in, but no one is available for months it seems, so will have to understand the installed logic and test things myself.
So my question is whats the normal logic for such a system? What sould control the main pump?, or should it just run?
Thanks in advance

 

[ShaunCorbs]

Check to see if you have voltage on the orange wires with the system off but pump still running

 

[taffyinhighlands]

Check to see if you have voltage on the orange wires with the system off but pump still running

Thanks for your reply.
Nothing on the orange wires, or anything else i can see, until i bring one of the heating loops live.
The pump cable sadly goes directly behind the plasterboard, with no junction box for the boiler which sits on the outside wall behind it.
There are 2 white 3 core leads labelled 'boiler swl,' and i think 'boiler line', with the swl one going to the orange group, but that seems to contradict to the other one also labelled boiler sw which also ties into the orange circuit.
Before i start cutting holes in the plasterboard, i'll look for any continuity between the pump and any of these wires, but logic wise, wouldnt it be normal to have the boiler and main pump switched on together? , and with the ufh being handled the same as one of the stardard logic controllers?

 

[Basher]

Not sure how into your boiler circuitry you are, so forgive me if the following is not clear, or indeed too simple.

As your system heats both hot water and radiators, then presumably you have an "S-plan" system (two 2-port valves, one for water, one for rads, or in your case, two for rads?) or a "Y-plan" system (with a 3 port valve - but maybe not with two zones). Knowing which you have helps as far as the wiring is concerned!
If you google those terms, you will find typical circuit diagrams on the web. They follow the same logic.

As you no doubt know, the label 'swl' is for the boiler switched live, which is the signal that turns it on, which comes from the orange wires on the motorised valves. The boiler also has a permanent live (in your case labelled 'boiler line'?) to power things that may need to run on after the heating has stopped.

The sequence of events when heat is needed is as follows: thermostat or tank stat calls for heat, the stat provides power to relevant motorised valve, valve gradually opens and at end of travel operates a microswitch (part of the mechanism), the microswitch connects orange wire to mains live (on grey wire), so boiler 'swl' is powered and boiler starts.

Some boilers can withstand the circulating pump being turned off at the same time as the boiler. In such cases the pump can be connected to the boiler 'swl'

Other boilers need (or prefer) 'pump overrun' to keep water circulating for a little while after thermostat has reached temperature and 'swl' is turned off. In such cases the boiler has a 'pump switched live' output to supply the pump.

Others here may already know or guess which type your boiler is. Maybe you could look at you boiler info to see if it has a dedicated switched live for a pump. If it does, you might be able to establish if that is doing what it should?
It sounds as if your pump is running when the orange wires have no power, so that seems to suggest the pump power comes from somewhere else (e.g. the boiler?).

 

[taffyinhighlands]

Not sure how into your boiler circuitry you are, so forgive me if the following is not clear, or indeed too simple.

As your system heats both hot water and radiators, then presumably you have an "S-plan" system (two 2-port valves, one for water, one for rads, or in your case, two for rads?) or a "Y-plan" system (with a 3 port valve - but maybe not with two zones). Knowing which you have helps as far as the wiring is concerned!
If you google those terms, you will find typical circuit diagrams on the web. They follow the same logic.

As you no doubt know, the label 'swl' is for the boiler switched live, which is the signal that turns it on, which comes from the orange wires on the motorised valves. The boiler also has a permanent live (in your case labelled 'boiler line'?) to power things that may need to run on after the heating has stopped.

The sequence of events when heat is needed is as follows: thermostat or tank stat calls for heat, the stat provides power to relevant motorised valve, valve gradually opens and at end of travel operates a microswitch (part of the mechanism), the microswitch connects orange wire to mains live (on grey wire), so boiler 'swl' is powered and boiler starts.

Some boilers can withstand the circulating pump being turned off at the same time as the boiler. In such cases the pump can be connected to the boiler 'swl'

Other boilers need (or prefer) 'pump overrun' to keep water circulating for a little while after thermostat has reached temperature and 'swl' is turned off. In such cases the boiler has a 'pump switched live' output to supply the pump.

Others here may already know or guess which type your boiler is. Maybe you could look at you boiler info to see if it has a dedicated switched live for a pump. If it does, you might be able to establish if that is doing what it should?
It sounds as if your pump is running when the orange wires have no power, so that seems to suggest the pump power comes from somewhere else (e.g. the boiler?).


View attachment 75530

Thanks, thats very clear. Its an oil boiler and i'll check through its documentation and its connections tomorrow, as all the microswitches on the 3 switched solenoid valves all appeared ok.

 

[taffyinhighlands]

Thanks, thats very clear. Its an oil boiler and i'll check through its documentation and its connections tomorrow, as all the microswitches on the 3 switched solenoid valves all appeared ok.

The boiler is a Grant Vortex pro, and looking at the wiring diagrams, i can't see that the boiler has an overrun conx to dissapate boiler heat, it just appears to tie into the switched boiler circuits??, and thus only run when triggered by one of the logic controllers.
I'll try to trace where the pump wiring goes now.....

 

[exedon2]

No pump overrun on a vortex pro
From a wireing point of view simple on/off boilers.

 

[Basher]

The boiler is a Grant Vortex pro, and looking at the wiring diagrams, i can't see that the boiler has an overrun conx to dissapate boiler heat, it just appears to tie into the switched boiler circuits??, and thus only run when triggered by one of the logic controllers.
I'll try to trace where the pump wiring goes now.....

Yes you're right, in that schematic the pump is wired to boiler switched live, ie the orange wires from the 2-port valves.
I would expect continuity between pump L and those orange connections.
Does your 'birds nest' actually implement that schematic 🤔!

Given it's apparently working other than the pump issue - I would be wary of 'tidying it up'. The choc block joints look well done, no bare copper on show, and there is a modicum of labelling, so I think it's OK to leave As is, at least for now.
The white sleeved flex with all the conductors cut off other than brown, routed out of the back, is presumably the switched live to the boiler? Maybe the pump is connected at the boiler?

 

[taffyinhighlands]

No pump overrun on a vortex pro
From a wireing point of view simple on/off boilers.

Thanks, time to trace that pump power!

 

[taffyinhighlands]

Yes you're right, in that schematic the pump is wired to boiler switched live, ie the orange wires from the 2-port valves.
I would expect continuity between pump L and those orange connections.
Does your 'birds nest' actually implement that schematic 🤔!

Given it's apparently working other than the pump issue - I would be wary of 'tidying it up'. The choc block joints look well done, no bare copper on show, and there is a modicum of labelling, so I think it's OK to leave As is, at least for now.
The white sleeved flex with all the conductors cut off other than brown, routed out of the back, is presumably the switched live to the boiler? Maybe the pump is connected at the boiler?

I'll also draw up a circuit from the birds nest, and although the temptation is strong to tidy it up, i think its a case of what aint broke, dont touch
Thanks

 

[taffyinhighlands]

Well, i'm going to take the easy route, and run a new cable to the pump. Without dismantling all the boiler panels n top i can't get to see its wiring so cant tell if the pump comes from there, and can't identify any of the wires anywhere in the birds nest.
It seems wired as per normal, the only confusing wires being those labelled boiler swl and boiler sw which are both tied to the orange control wires from the 3 servo valves. With the addition of a 13amp flat power cable with some indecipherable label, see photo, i still struggle to see how the ufh triggers the boiler (unless its the black wire, or the boiler sw wire), but thats for another day.

Thanks for everyones help - makes a real difference getting experts input & advice

 

[Basher]

Well, i'm going to take the easy route, and run a new cable to the pump. Without dismantling all the boiler panels n top i can't get to see its wiring so cant tell if the pump comes from there, and can't identify any of the wires anywhere in the birds nest.
It seems wired as per normal, the only confusing wires being those labelled boiler swl and boiler sw which are both tied to the orange control wires from the 3 servo valves. With the addition of a 13amp flat power cable with some indecipherable label, see photo, i still struggle to see how the ufh triggers the boiler (unless its the black wire, or the boiler sw wire), but thats for another day.

Thanks for everyones help - makes a real difference getting experts input & advice

Well done making progress.
My thought is "boiler swl and boiler sw" both mean "switched live" but don't necessarily mean a wire going to the boiler!

For the 'switched live' group that you've identified, each wire is either:
(1) a source of power - eg motorised valve (x 4), tank stat, ufh,
or
(2) a load - eg boiler and pump, but I can't think of anything else (not ufh if its pump is switched by its thermostat)
Considering your diagram, I would expect eight connections in all, but can only see six in the photo.

I also cannot decipher the writing on the white cable. You probably know that 3 core & E cable colours are typically wired brown (L), grey (N) and black (sw L), of course inconsistent with motorised valve flex colours, and old red & black, where black was (N)!

One way of identifying the mystery connections would be to disconnect one at a time (power off obviously), and try and find what's stopped working! With care, a voltmeter on the disconnected wire would determine if it's a power source, or a load, if power is temporarily restored.
However, just to get it going, a new cable to the pump seems a good test. Just be sure power for all components of the system continues to come from the same fused spur/ single circuit breaker in your consumer unit. Don't 'borrow' a neutral from somewhere else, or you may have tripping rcd's!
Good luck solving the riddle!

 

[taffyinhighlands]

Update - well, I should have heeded @ShaunCorbs post a bit closer

I ended up removing the orange wires one by one and found it was the towel rail actuator that was always active. Since the towel rails are needed, I've swapped with the upstairs rads for now - taking the cover off the Danfoss HPA2 cover it doesn't look very user serviceable - I've exercised the actuator a few times, but no change - is it just a case of nice paperweight now and get a replacement?

thanks

 

[Basher]

I've exercised the actuator a few times, but no change - is it just a case of nice paperweight now and get a replacement?

I'm not familiar with the innards of that actuator - probably best to replace 🤔

 

[ShaunCorbs]

Sorry to say yes also they don’t like being left open or closed they need to keep moving else they stick / motors burn out

So it might be best to have a redesign if you want the towel rads always on / timed leave the valve head off and body fully open and rewire it to a timer