Cylinder wiring

[LondonFoy]

Hello.

Drayton HT3 tank thermostat wiring?

Common, call for heat, satisfied. Simples!

Just swapped thermostat out as old was faulty. Think there’s also a wiring issue?

Satisfied seems permanently live. HW is off on controller. When plate at back depressed, common turns live so circuit is satisfied and common as loop. Call doesn’t get any juice.

With HW on, common live, satisfied live, call live, when backplate depressed common is live, satisfied is live, call is dead.

Where should the permanent live go to, common, right?

Then the call and satisfied make the loop accordingly to thermostat setting? No?

The issue is when controller turns on, whatever temp thermostat is set, boiler continues to heat, until controller turns off, not as should be when reaches thermostat temp.

 

[RepairingDave]

A photo of the connections might help.

With HW on, common live, satisfied live, call live, when backplate depressed common is live, satisfied is live, call is dead.

I'm not sure what to backplate is - what should happen when it is depressed?

 

[stem]

You don't say, but assuming that you have a mid position 3-port valve...

Satisfied seems permanently live. HW is off on controller.

The above would be correct. HW satisfied (aka hot water heating not required) gets its live from two places 'satisfied' from the cylinder thermostat and 'HW off' from the programmer. So if HW is off at the programmer, then cylinder thermostat 'Satisfied' should also be live.

Can't comment on your other points as I don't really understand what you mean. However, here's how it should be:

Common (C in drg below) - Goes to 'HW On' at the programmer
Call (1 in drg below) - Goes to boiler switched live [starts the boiler when heat is called for]
Satisfied - (2 in drg below) - Goes to motorised valve grey wire and 'HW Off' at programmer

 

[LondonFoy]

Thanks. After further troubleshooting, I might have found the problem. The satisfied is loose and not connected in the junction box, so not telling HW off in the controller. I’ll reconnect and try again. 3 port valve cable is black, bottom left. The grey is connected at the bottom of the chock block, and the brown going in top is the Hw off controller feed, but that other grey, is the satisfied.

 

[LondonFoy]

So, checked and fixed all wires. All are lined up as they should be and match the y wiring diagram. However, HW still doesn’t switch off. Have set new tank thermostat to 50, which is lowest before permanently off ( when I turn permanently off, it does switch heating off). The boiler and pump are still called for.

When checking the placement of tank thermostat, it’s clean inside the insulation cut to the brass tank, the level is about right at 1/4 - 1/3 from bottom, but when touching the bare brass and holding my hand there, it’s really not that hot, yet the water out the taps is significantly hotter (don’t have thermometer to take actual readings), system was fully yet washed/descaled/etc nov 23, but I’m now wondering if there’s sediment at the bottom of the tank, therefore reducing the stratification?

 

[stem]

When checking the placement of tank thermostat, it’s clean inside the insulation cut to the brass tank, the level is about right at 1/4 - 1/3 from bottom, but when touching the bare brass and holding my hand there, it’s really not that hot, yet the water out the taps is significantly hotter

That's normal. The thermostat is calibrated during manufacture to take that into account.

The cylinder thermostat is quite easily tested, when the hot water cylinder is at the temperature you want, turn the thermostat up and down until it clicks on/off. The point between the two clicks should correspond to the temperature of the water at the top of the cylinder that would go to the taps.

With the CH off and the HW on, turning the cylinder thermostat up and down until it clicks on/off should also start/stop the boiler. If the boiler doesn't stop when the thermostat is 'off' here are some possibilities.

Faulty cylinder thermostat
'Hot Water Off' signal from programmer, or cylinder thermostat 'Satisfied' not connected to motorised valve's grey wire.
The central heating is running the boiler
Faulty microswitch inside mid-position motorised valve

HW still doesn’t switch off. Have set new tank thermostat to 50, which is lowest before permanently off ( when I turn permanently off, it does switch heating off). The boiler and pump are still called for.

There is no such thing as "permanently off" It's a thermostat and controlled by temperature, if the temperature of the water in the cylinder drops below the chosen setting it will turn on.

The cylinder thermostat should not have any effect on the operation of the central heating. HW and CH are separate functions. If it is controlling the CH something is definitely amiss, and someone with a working knowledge of a Y-Plan that is competent in using a mutlimeter will probably need to check the system through.

 

[LondonFoy]

Thanks…

So I can confirm that CH thermostat doesn’t affect HW.

All wiring is now correct, and tight, and lines up with normal Y plan schematics.

3port valve body is working and free.

3port mid position head is new, and wired correctly.

Tank thermostat is new and wired correctly.

When tank thermostat is barely registering above the off-click-setting, and below the 50 mark, so probably around 35-45 degrees setting, it works the way it should.

My question regarding debris/limescale build up in cylinder, is the difference in temps from top to bottom, is significant, more than you’d normally find and the bare patch, barely gets hot, more a like warm. Usually I can feel a good heat from cylinders in that patch with my thumb, not this one.

I guess, drain the cylinder and pop the immersion to take a look inside and maybe descale?

All electrics appear to be doing their thing, and I’m loathe to think a brand new tank stat would be faulty from the box… but, never say never…. I can’t think of any other way to go as everything else I can think of, now checks out…. Have I missed something ?

 

[LondonFoy]

When I meant permanently off, it’s the Drayton ht3, and the new one has a final click for 0, that is a complete ‘off’.

 

[stem]

The cylinder thermostat can be easily tested with a multimeter. disconnect it from the heating wiring and with the multimeter set to Ohms [Resistance] measuring between: -

Com and Call = Should be 0Ω when the thermostat was 'on' infinity when 'off'

Com and Satisfied = Should be infinity when the thermostat was 'on' and 0Ω when 'off'

barely gets hot, more a like warm.

That's usually the way I find it. Cold water from the storage cistern comes in at the bottom of the cylinder. After the cylinder has been replenished after using hot water it can even be cold to the touch.

However, easy to test, if the HW doesn't switch 'on' and 'off' as you manually turn the thermostat up and down, then there is a fault with the controls. If it does work when you do that, then maybe not.

 

[stem]

When I meant permanently off, it’s the Drayton ht3, and the new one has a final click for 0, that is a complete ‘off’.

Really?

If by 0 you mean the symbol at the bottom it's °C as in Degrees C, the value it is measuring. It will click off when sensing a value below its set temperature.

 

[Johntheo5]

A relatively easy "mechanical" test is ensure both CH & HW switched Off, go to the MPV, there should be a immediate fairly stiff resistance when you start pulling the manual lever across to the mid position, switch on the HW and turn up the cylinder stat fully, the same resistance should be felt when pulling the lever across, the boiler should fire. Leave HW programmed ON but turn the cylinder stat down fully, the boiler should stop.

Electrical test, switch HW on, but cylstat turned fully down, (on the cylstat) you should get 230V between C & N (orE) and 0V between 1 & N (orE), turn the stat up fully, you should then get 240V between 1 & N (orE).

 

[LondonFoy]

Yes, that’s the old ht3, the new one is slightly different with an extra, off position but right at the bottom. You see the different screw position. Everything else is the same, except the extra off. It’s an extra hrs click, not a marking. You see how low the setting has to be for it to slightly work. I’ll get a thermometer and get some propert water temp readings. I’m getting a flow of 38c into the coil reading a radiator strap thermometer, and there’s a good difference on the return, so it’s working.

 

[LondonFoy]

A relatively easy "mechanical" test is ensure both CH & HW switched Off, go to the MPV, there should be a immediate fairly stiff resistance when you start pulling the manual lever across to the mid position, switch on the HW and turn up the cylinder stat fully, the same resistance should be felt when pulling the lever across, the boiler should fire. Leave HW programmed ON but turn the cylinder stat down fully, the boiler should stop.

Electrical test, switch HW on, but cylstat turned fully down, (on the cylstat) you should get 230V between C & N (orE) and 0V between 1 & N (orE), turn the stat up fully, you should then get 240V between 1 & N (orE).

Mechanically, the 3 port head is operating properly. My multimeters broke, so I’ll get a new one as well as a water temp guage and try further.

 

[LondonFoy]

The cylinder thermostat can be easily tested with a multimeter. disconnect it from the heating wiring and with the multimeter set to Ohms [Resistance] measuring between: -

Com and Call = Should be 0Ω when the thermostat was 'on' infinity when 'off'

Com and Satisfied = Should be infinity when the thermostat was 'on' and 0Ω when 'off'



That's usually the way I find it. Cold water from the storage cistern comes in at the bottom of the cylinder. After the cylinder has been replenished after using hot water it can even be cold to the touch.

However, easy to test, if the HW doesn't switch 'on' and 'off' as you manually turn the thermostat up and down, then there is a fault with the controls. If it does work when you do that, then maybe not.

Thanks. Yes, the HW turns on and off when adjusting the stat, but it only really registers right down the bottom of the measurements. So I know electrically, it’s working. I’m just perplexed as to why I need to be setting it almost off to get the temps of the taps down.

 

[Johntheo5]

There should be ~ 8 to 10C difference max between clicking up and clicking down the stat, if the tank temperature is say 40C then just turn the stat fully up and then slowly keep turning it down near the 40C mark until you hear a click, then turn it up very slowly until you hear another click, should be around 8C to 10C max between clicks, stat hysteresis.
I've installed a few of these for relations, I just tried the hyseresis on this new spare and its only ~ 6C, it seems to have a better defined scale than the HTS3 above.