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Plumberpro
Plumberpro, Home Appliance Technician
Category: Appliance
Satisfied Customers: 634
Experience:  Heating and hot water heating appliances experienced
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I have a ST9400c programmer. I leave the heating on 'constant'

Resolved Question:

I have a ST9400c programmer. I leave the heating on 'constant' and water on 'auto'. The heating switches itself to 'off' apparent reason, usually overnight and about 3 times a week. Have had the unit replaced and the problem persists.
Submitted: 1 year ago.
Category: Appliance
Expert:  Plumberpro replied 1 year ago.
Plumberpro :

, do you have a room thermostat?

Customer:

I have one thermostat home. I live in a bungalow

Plumberpro :

Ok . it could be the thermostat. What temperature do you have it set at and where aboutvis it located?

Customer:

I have it set to 23 C and it is located outside the cuboard where the programmer is. I have a air heat pump system installed if that is relovant

Plumberpro :

Is the thermostat in a place that is quite warm or liable to heat up quite quickly?

Customer:

yes it is in a cosy position. I have had a termometer by it and it indicates that it is not over heating

Plumberpro :

Its recommended to nput the thermostat in a cool position , with no radiators, to avoid the stat reaching temperature before the rest of the house. This is xwhy they are usually positioned in the hallway . if your room statvis wireless you could try it there not near a radiator/ heater

Customer:

It is in the hallway not near a radiator. How can it cause the programmer to switch itself form 'cont' to 'off' mode by itself

Plumberpro :

Do you mean that the heating is not switching off because it is reaching the temperature set by the room stat , but the programmer is turning itself off ?

Customer:

yes that is correct and most mystifying

Plumberpro :

It sounds like the programmer is on programmed time and not constant. Is there a separate control air heat pump?

Customer:

not a separate timer on the air heat pump side. It has controls temp and there is an immersion heater it wants to heat water to 60 C to prevent bacteria

Plumberpro :

Does it have a control panel with a menu and display?

Customer:

yes

Plumberpro :

There may be something on there that is controlling when it operates. Is it very complicated , do you know how to use it ?

Customer:

rather beyond my expertise It is a mitsubishi electric

Plumberpro :

Ok . are you still in touch with the installer? I could try and find a manual if you have the model , but a call to the installer may save hours of confusion

Customer:

par-w21maa-j is written on the controller. I have been through checking this controller with the installer and they do nothing except tell me that the st9400c is not working. st9400c is now out of warranty so that are reluctant to help me

Plumberpro :

K . give a little while , I'll see if I can find a manual , thanks

Plumberpro :

, there is a timer on the controller. Is anything lit or showing on the display , especially in thecvleft hand corner?

Customer:

it is showing 'heating eco' at the top left. under that is 37 which is the target temp of the water I have pressed the 'menu' button and it says not available. There is a button which says 'on/ff' but this comes up with 'not available' as well


Plumberpro :

Ok. Is there function displayed with a line through it? The controls may have been locked

Customer:

Cannot see anything with a line through it. Can this unit send a signal to the st9400c to tell it switch off?

Plumberpro :

No the programmer goes to the room stat then to the air pump controller. As the air pump controller is last in line it can override the programmer and room stat

Customer:

So it has to be an error in the programmer

Plumberpro :

No . the air pump controller.

Plumberpro :

The air pump controller , which has been locked , is turning the unit off overnight

Plumberpro :

Do you want to try and unlock the air pump controller ?

Customer:

nothing to loose unless it goes completely wrong. Does this sound favourite

Plumberpro :

Thats what I'm a bit worried about . if it does you may be without heat while. But if you are confident we can go ahead

Customer:

when you say a while would it be minutes or days? I could contact the installer as the mitsubishi parts are still in warranty but they do nothing but blame the programmer and I doubt they would help

Plumberpro :

Ok . let's do it then . press and hold the button , cir.water and the button marked on/ off seconds. This should unlock it

Customer:

did that It asked to change language which I left alone now it says 'locking function off'

Plumberpro : Ok, hold down timermenu button fir 3 seconds.. Set up should appear on the screen.
Plumberpro : Then press the monitor set button to set the off time as shown on the display
Customer:

timermenue button not changing anything when help down

Plumberpro : Does anything come up on the display" like timer set ,enter and a time.
Customer:

I've got 'time set enter'

Plumberpro : I Ok , do you have a number anywhere on the display?
Customer:

I have time 2008

Plumberpro : Ok , use the arrows to increase the time . Monitorset day buttons
Customer:

set to 2015 now

Plumberpro : ok , will it keep going up until the time you want it to turn off?
Customer:

tell you what now I think I will contact ice energy to talk me through your ideas as I can see this going on long time I could try to find a manual on-line to walk through(can you direct me to a manual) But I feel out of my depth now.

Plumberpro :

Mitsubishi Electric PAR-W21MAA Operation Manual . this brings up the manual . they make these things so complicated . its so much easier when its in front of you .

Customer:

OK that's fine Thanks help Are you confident that this will stop the programmer switching off as I don't see how the air pump controller can tell the programmer to shut off?

Plumberpro :

Yes . totally sure this is where the issue lies. All the best . it is getting late . if you want to carry on tomorrow then that's fine

Customer:

I'll read the manual and contact the installer. They should be able to walk me through it on the phone. I think you have helped me all you can and I'll rate you as good service so you get paid

Customer:

Thanks again

Customer:

Mickey

Plumberpro, Home Appliance Technician
Category: Appliance
Satisfied Customers: 634
Experience: Heating and hot water heating appliances experienced
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