Air source heat pump heating issue

It is yes

solarsavings said:

The programmer you have, is it a Honeywell ST9400c ?

Click to expand...

It is yes

I did ask to see your controls in another post as I suspected that you had that programmer.

Turn off the demand for hot water and heating.

Turn the cylinder and room stats up to ensure they both call for heat. (make sure you turn the cylinder down again when you have tested the programmer)

Using the override buttons you should see the green lights and hear two distinct clicks. The sound of the clicks are the important bits, so listen for them both.

If you only hear one click then the programmer is at fault.

solarsavings said:

I did ask to see your controls in another post as I suspected that you had that programmer.

Turn off the demand for hot water and heating.

Turn the cylinder and room stats up to ensure they both call for heat. (make sure you turn the cylinder down again when you have tested the programmer)

Using the override buttons you should see the green lights and hear two distinct clicks. The sound of the clicks are the important bits, so listen for them both.

If you only hear one click then the programmer is at fault.

Click to expand...

Just done as you described, heard 2 clicks

Sorry to resurrect an old post but I'm still having this issue.

I have established that the microswitch on the Mv is fine, i had a look at the junction box and it's a hell of a mess in there, i can see about 6 or so white wires, all labelled with numbers (I assume in relation to the port on the HP) there is a bunch of wires connected to these white wires, MV's prorgammer etc etc

I suspect there is either a broken connection or another error with the POS HP itself, any ideas?

What is the make and model of the ASHP please?

Speed reading this thread did I pick up correctly:

1a. you have a hot water tank and separate buffer hot water tank?

1b. The buffer tank contains the heated water for the radiator circuit?

2. as far as you know the installation control is S plan or some derivative of it?

3. you have a room thermostat(s), a hot water tank thermostat and a buffer tank thermostat?

4. One pump.


Did the system ever work correctly?

What solenoid valves do you have and their type - just post a picture of the label on them or the part number and make.

Please draw a sketch of the valves, pump, ASHP, tanks, rads water circuit.

marconi said:

What is the make and model of the ASHP please?

Speed reading this thread did I pick up correctly:

1a. you have a hot water tank and separate buffer hot water tank?

1b. The buffer tank contains the heated water for the radiator circuit?

2. as far as you know the installation control is S plan or some derivative of it?

3. you have a room thermostat(s), a hot water tank thermostat and a buffer tank thermostat?

4. One pump.


Did the system ever work correctly?

What solenoid valves do you have and their type - just post a picture of the label on them or the part number and make.

Please draw a sketch of the valves, pump, ASHP, tanks, rads water circuit.

Click to expand...

Correct, it has never worked correctly since I moved in, i can't say if it ever worked correctly.

It's an ideal airtherm 4.5

The third pic is of the 3 way valve, it doesn't seem to work when hot water or heating is on (had the cade off when it was running, no movement on the valve) this is on the buffer tank

Re your #53 - is there a link between terminals 11 and 12? I cannot tell from the image.

Such a link seems to be required for simultaneous space and water heating according to the manual. Do not put one in if there is not one just yet.

I will read the ASHP manual this evening to avoid suffering BGT or SCD.

marconi said:

Re your #53 - is there a link between terminals 11 and 12? I cannot tell from the image.

Such a link seems to be required for simultaneous space and water heating according to the manual.

Click to expand...

There are 2 wires coming from 11 and 12, i cannot tell if they are linked but there are no wires at the bottom of the terminals, would you like me to test for an open circuit between 11 and 12?
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I should mention that there is heating when the hot water is on but the CH does not work independently of the hot water. I have to have both on in order to have heating and once it hits temp i have to run the hot water until the HP kicks in so I have heating again.

No don't do any measurements.

So the fault is that the ASHP will never run up in demand to a space thermostat to warm the water in the buffer tank?

Please confirm whether there is a 'stat on the buffer tank - I'd expect to see one.

The programmer does have HW and CH selected to on and either in a timed on period or sert to constant?

marconi said:

No don't do any measurements.

So the fault is that the ASHP will never run up in demand to a space thermostat to warm the water in the buffer tank?

Please confirm whether there is a 'stat on the buffer tank - I'd expect to see one.

The programmer does have HW and CH selected to on and either in a timed on period or sert to constant?

Click to expand...

That's correct there is a stat on the buffer tank, all pumps and MVs work when heat is called for just not the heat pump.

And yes the programmer works correctly.
See pic of stat on buffer tank and stat on HP itself, HP turns off when this reaches 55.c

I have enough now to be getting on with. I hope to reply tomorrow morning.

marconi said:

I have enough now to be getting on with. I hope to reply tomorrow morning.

Click to expand...

Thank you, please see added pic to above post of stat on HP

There is a rectangular junction box with a yellow warning stick on it near the tanks and valves. Could you carefully remove the lid and take a photo of its innards for me?

I think you said the water pump does not run when only the CH demands heat - am I correct?

What I would suggest if you feel able and safe - is to do a quick wire change. Before you touch any wiring you must isolate all electricity and check afterwards it is dead - do know how to do that? The easiest way to isolate is switch off the home main switch/switches which is what I recommend you do.

What we are going to check is the operation of the 2 port Motorised Valve(2PMV) for the CH circuit and check that the water pump starts.

To do this we are going to disconnect the white wire at terminal 13 at the ASHP and label with tape or a marker pen or note the number on it so its purpose is not lost. Put its end in a connector block or WAGO and then move it of harm's way.

Now, remove the wire from terminal 10 and insert it into terminal 13 and tighten up.

Re-connect power.

Set the programmer to 'Constant HW' (or advance the switch on or press override for HW).

Next we need to create a demand for HW (yes HW) by running off from the HW tank or turning up the HW set temperature. The latter is the easiest and quickest but up to you how. Now go to the water pump and observe the green lights on it. When a HW demand is created does the water pump start? If it does, go and see of the ASHP starts - it may take a little while. If the ASHP starts wait a while and feel the radiators to see of they become warm. If the pump does not start, it may be the HW demand has not been signalled so run off some hot water to much reduce the tank water temperature. Unless a demand for HW is generated the test will not begin.

Turn the HW tank stat to its lowest set temperature, when the demand for HW ends, the water pump and ASHP should shut down.

That's the end of the test. So isolate electricity and return the white wires you removed to their original terminals.

I look forward to hearing the results. We are checking the external logic ' demand 2PMV(CH) opens and when opened start water pump', and the ASHP internal logic 'if circulant water flow detected and there is an >?? Celsius temperature difference between out and return then start ASHP'

I won't give any more explanation to avoid confusing you.