Fitting new 5111603 PCB to suprima 50

[Grindstone]

Hi Ok run it all ways I think

No power to the switch and it rests at H.

HW on, no demand for heat at the room stat, CH off.
Switch moves to W, boiler fires

HW and CH on Room stat demands heat,
Switch moves to M, (midway) boiler fires

HW off, CH on demand for heat at room stat
Switch moves to H, but the boiler won't light

If HW and CH are both on boiler lights if there is a demand for heat from the room stat, but once its satisfied it continues to fire, i.e. the rads stay on and the house gets hotter and hotter.

Does this help , any other test I can do?

 

[matt1e]

ok if the hot water and the central heating are both switched on and the room stat is down does the boiler light?

if not does it then light if the cylinder stat is turned down?

 

[MANDATE]

Hi Ok run it all ways I think
No power to the switch and it rests at H

(wrong! should go to Water if there is no power)
If you removed all power, there would be nothing to hold the valve at Heating.
If you just turned the HW and CH off, power on the 'grey' would remain and that would keep valve at H.

HW on, no demand for heat at the room stat, CH off.
Switch moves to W, boiler fires

(this is satisfactory)

HW and CH on Room stat demands heat,
Switch moves to M, (midway) boiler fires

(this is satisfactory, turning on room stat sends power to valves 'white' wire which drives valve to mid position, boiler fires due to cylinder stat)

HW off, CH on demand for heat at room stat
Switch moves to H, but the boiler won't light

(this is basically correct because 'grey' takes over from the 'white' and should fire if micro switch was ok)

If HW and CH are both on boiler lights if there is a demand for heat from the room stat, but once its satisfied it continues to fire, i.e. the rads stay on and the house gets hotter and hotter.

( When both HW and CH are switched on, it does not necessarily mean both are receiving heat. The heat will be shared if both are in demand, but when one side gets satisfied the valve moves to close the port and open the opposite port fully).

Whilst I'm still convinced micro switch is a problem, it is not clear if wiring is in accordance with 'y' plan diagram.



[/quote]

 

[matt1e]

Grindstone wrote:
Hi Ok run it all ways I think
No power to the switch and it rests at H

mandate wrote

(wrong! should go to Water if there is no power)
If you removed all power, there would be nothing to hold the valve at Heating.
If you just turned the HW and CH off, power on the 'grey' would remain and that would keep valve at H.

yes I totally agree with mandate and the rest of his post
its this part that has me thinking that there is a problem with the wiring

If HW and CH are both on boiler lights IF there is a demand for heat from the room stat, but once its satisfied it continues to fire

fair enough if the cylinder stat is satisfied or stuck in the satisfied position then of course the boiler would only fire on room stat demand but if that was the case then
1) why does it not switch off when satisfied
2) why does it then work if HW only is selected

matt











2) why does selecting HW only then work ok

 

[Grindstone]

Ok, I'm in work now, but tonight I'll cut the power to the house and see if the switch then moves to W, i.e. no demand.

The stat on the hot water tank is set at 70c, I can turn this down to 60, will that help? I guess what's missing here is what happens when the switch is midway, CH and HW on but the HW stat is at temperature?


As far as I can see at the moment, when HW is on CH is on, the switch is at midway position, but the rads won't get hot until the room stat demands heat. Once it does the rads get hot, but when the temp goes past the stat temp the heat stays on. No idea what is happening with the water.

As I say I'll cut the power and see if that moves the switch to W as per mandats earlier post.

Thanks

 

[MANDATE]

In each situation there are two essential requirements (a) how to get the valve to the correct position and then (b) how does the boiler light.

With HW only it is fairly simple. No power on the 'grey' wire and no power on the 'white'wire. The return spring unwinds the motor so valve is at HW.
The boiler lights because HW is switched ON (and in demand). The HW ON wire feeds the cylinder stat which fires the boiler, until its satisfied.

If we jump to CH only it's a bit more complicated. Say valve is at HW position, but HW is not switched on. Its done in two stages with two power supplies.
First stage. The CH ON wire feeds the room stat, this in turn feeds the 'white' wire of the valve. This drives the motor until it triggers micro switch No 1.
Second stage. There is a HW OFF wire and this feeds the 'grey' wire of valve. (this is live because HW is OFF). The triggering of M/S No1 is just switching power from 'white' to 'grey' at midway so the valve can continue to CH only.
In this situation there is no HW or cylinder stat involvement, This is where another M/S No 2 comes in. During the second stage this M/S No 2 is triggered. This allows power (which also comes from the 'white') out through the 'orange' wire to light the boiler.
When CH is satisfied, the room stat cuts the power so boiler stops, but valve does not move, cause its not the 'white' thats keeping it there it's the 'grey'

Now for the most complicated.
When HW and CH are switched ON, it does not automatically mean the valve goes to mid position. It all depends what is in demand and what is satisfied.
The valve moves according to the demands met.
If HW satisfied valve moves to CH
If CH satisfied valve moves to HW
If both are in demand valve moves to middle.
Looking at these three positions, the last two involve HW and cylinder stat lights boiler, but it relies on the M/S No 2 for CH only.

Also if both HW and CH are in demand and valve is at midway and CH becomes satisied before HW (can't see it myself), the room stat would cut off 'white' supply and valve would go to HW only

When both HW and CH are in demand the radiators get a share of the water. (boiler lit by cylinder stat) As soon as HW is satisfied (boiler stops)its supposed to move the valve to CH and re-ight boiler (by M/S No 2).
In some cases the valve does not move to CH and in some cases it does, when it does and boiler does not light it points to M/S No 2 being at fault.

There appears to be some doubt regarding the wiring. or is it more misunderstanding. Don't know?
sorry for a long winded episode, just thought it may help to clarify things.

 

[Grindstone]

All making sense,

Got home and the house is at 24c way past what the thermostat is set to. Cut the power to the house and the valve goes to W.

Power back on CH and HW on and set the thermostat to 27c, boiler did not fire.

increased the stat on the HW cylinder to 70c and the switch went to midway, boiler fired.

Moved the cylinder stat switch back, boiler went off switch went back to H, boiler went out.

Decreased the room stat, boiler stayed off, the rads are now colling slowly and I guess will stay off until I use some hot water or increase the cylinder stat?

Does this help at all?

 

[Grindstone]

Ran some hot water off and the boiler has fired again, switch is now at midway position, even though there is no demand for CH just water, the rads are staying cool,

If it follows what normally happens now the house will cool until the room stat demands heat and the rads wil heat up, and keep heating up until I turn the HW off at the clock.

 

[Grindstone]

Sorry update on the last post I was perhaps too quick, the switch is now at W boiler is on the rads are cool and the room thermostat is not demanding heat, so all good and I guess as its should be, until the room stat demands heat, and then won't turn off the demand.

Does this take us back to the micro switch?

 

[matt1e]

hello again
nice explanation mandate! and again I agree with your diagnosis of the valve
no misunderstanding of how they're wired here either I've done 100's of them! but I only agree up to the point that its assumed the wiring is correct
which I don't think it is look at it this way here is an excellent diagram I found elsewhere on this site

now I'm sure you will agree that this is the correct way of wiring Y-plan

now taking the ORIGINAL problem

however the problem is that the water must be on to make the heating come on! The thermostat works to send a demand for heat, but will not turn the heating off, it just gets hotter and hotter until I turn the water off, then the boiler goes off.

right the first part of the problem up to the explanation mark does indeed point to the bottom micro switch in the valve being at fault or a loss of continuity between the orange wire and the boiler but then you get to the

The thermostat works to send a demand for heat, but will not turn the heating off, it just gets hotter and hotter until I turn the water off, then the boiler goes off.

now I cant see anything in a correctly wired system that would cause this certainly not a open circuit micro switch there has to be other issues for me
matt

 

[MANDATE]

All making sense,

Cut the power to the house and the valve goes to W.

That's what it should do! It seems all power was not removed previously.

Power back on CH and HW on and set the thermostat to 27c, boiler did not fire.

Depends what demands were already met. If HW was satisfied then valve would move to CH only, but (faulty) M/S No 2 would prevent boiler firing.

increased the stat on the HW cylinder to 70c and the switch went to midway, boiler fired.

That would make sense to me. If the demand was for both HW and CH.
cylinder stat lights boiler. But if CH was satisfied then valve would/should have gone to HW only (still fired by cylinder stat).

Moved the cylinder stat switch back, boiler went off switch went back to H, boiler went out.

I assume the room stat was satisfied cutting off the white supply causing valve to drop back. HW was satisfied so no firing boiler through cylinder stat. I think I'm happy with that

Decreased the room stat, boiler stayed off, the rads are now cooling slowly and I guess will stay off until I use some hot water or increase the cylinder stat?

It does seem that room stat is doing what it should through the 'white' wire and the 'grey' wire is doing its job. When you put in your new valve/head it will be clear if there is any other wiring problem.

For testing purposes its best to avoid have both HW and CH switched on together, because of the confusion.
I would try HW only and turning cylinder stat up/down to fire and stop boiler.
Then I would try CH only with stat turned down first, then turn stat to watch valve move first to midway then on to end. Then turn stat down and valve should stay put.
Mind you I'm not in the trade, I've only worked on one system with a mid position valve.

 

[matt1e]

hi again grindstone
reading your last 3 post apart from the fact that the stat wont control the heating (off) it does look as though the wiring is correct as far is the valve is concerned i'm wondering if the valve and the stat are knackered or the valve could also be sticking open
try setting heating and hot water on room stat off and cyl stat up
the boiler should fire and the valve should be at W
now turn the cyl stat down the boiler should go out and the valve should still be at W
now turn the room stat up the valve should move past the M and onto the H
the boiler should now fire if it doesn't this is usually indicative of a bad micro switch or orange to boiler connection
now turn the room stat back down and the cylinder stat up
check that the valve returns to W (give it a little time)
now with the cylinder stat still up turn up the room stat
the valve should move to the M position
turn the room stat back down
the valve should return to W

matt

 

[MANDATE]

Hi Matt!
Although this problem looks solved, I have to agree there might be other issues.
Unfortunately it needs hands on examination to verify that the wiring conforms to the diagram (which I agree is correct).
I don't know if 'grindstone' is in a position to trace and verify the wiring conforms, but it would help.

 

[matt1e]

hi mandate

don't know if 'grindstone' is in a position to trace and verify the wiring conforms, but it would help.

Yes I agree again
Does look as though we are getting somewhere though



regards
matt

 

[gavinda]

am i missing something or are you trying to diagnose an electrical fault woithout a multi meter. if so. stop. you're potentialy going to hurt yourself or someeone else. you also are going to waste money throwing unneccesary parts at the heating system. just payout for someone who knows what they're doing and this'll probly get solve in les than 2 hours much less 2 weeks.