Danfoss 40704 TP4000/5000/5000S/5001+RF Heating Control Stopped Working.

[Traveller]

Hi all.

It was working fine and then suddenly stopped working. Radiators not working but hot water is. Workmen were working at the house to repair a leaky roof and I found the property's fuse box cabinet open, so I am not sure if it could be the workmen that broke it or if it could possibly be water damage. I am not sure how to tell which exact model it is but it looks like the one in the picture below.

https://plumbers.s3.eu-west-1.amazonaws.com/data/attachments/44/44392-2521d6a1c3cf32b323a66d3fab16d632.jpg

The display is completely blank. I have tried new batteries but that hasn't made any difference. I have read that if it needs replacing, it needs to be replaced by the same item as it needs to match with something in the boiler (Vaillant ecoTEC plus). Is this true?

Are there a million things that could have gone wrong with it or can anyone suggest the most common likely issues?

Thanks.

 

[terryplumb]

Are you fitting the batteries correctly ,they are not both fitted with the + signs at the same end ?
Show us a pic of your actual unit

 

[Traveller]

Thanks for the reply, terryplumb.

Yes, I inserted them correctly.

Sorry, the photos aren't very good!

 

[terryplumb]

Is the polarity of the batteries correct ,beneath them is a pictogram of which end is + and - .
Have you tried pressing the reset button ?

 

[ian1182]

You can reset the unit as follows

Partial reset: Press RESET (used to restart micro-computer) if display
freezes for any reason. This does not reset any programme, clock or
date. It is recommended that this is done at time of installation.

User full reset: Press RESET whilst holding down PROG button. This
resets event times and and temperatures back to the factory presets.
The unit must be re-programmed. The correct time will be retained.

As it's battery powered the appearance of something on the display is independent of your boiler, fuse box, etc.

If that does not work, then it probably needs replacing by another battery powered programmable thermostat. For example Honeywell T3/T4 or Drayton Digistat battery. There are a number of similar battery powered models available. You could also look for something 2nd hand on ebay.

 

[Traveller]

Thank you for the replies and advice.

terryplumb, yes, I've taken more photos to illustrate there is no error regarding polarity or batteries. As you can see, I've even tried taking out the old Duracell batteries in the previous photo and replaced them with new batteries. I also rubbed the slightly green contact on the bottom left with paper. Yes, I pressed reset also. I also tried inserting one of the batteries the wrong way round because both negative ends of the unit have the springy metal contacts and usually, the metal springy contact is on the negative side in most appliances.

ian1182, yes, I pressed reset whilst holding prog and vice versa. The reason I mentioned the fusebox was not that I thought it was connected to the issue, but because I thought the workmen might have gone to check the fusebox when the heating control didn't work for them, but that's all just pure guessing.

Thanks for the suggestions of other units, but how do I make sure which ones are compatible? I had already checked ebay for the same model and didn't realise they were so expensive!

Also, if the unit is wireless, shouldn't there be a receiver near the boiler? I'd have to double check, but I don't think I noticed one!

Thanks.

 

[ian1182]

I believe you will find that your thermostat is a wired model. There are a number of replacement wireless models but will be more difficult to fit as the receiver unit is generally mains powered.

The easiest would be a straight swap for another battery powered wired model such as the Honeywell T3/T4. The T4R is wireless if that's your choice

 

[Traveller]

Thanks ian1182. I have a few questions.

If it's wired, should I have the wires/connections checked first in case it's a wiring fault before purchasing a new unit? I probably won't be touching any wires myself but if I wanted to inspect it visually for any obvious loose connections, etc, do I just prise the front panel open with a screwdriver?

Why doesn't the heating work without the unit? I never use any programs anyway. Is it because it might also have a built in thermostat?

If it is wired, does that mean that any (or almost all) units would be compatible with the boiler? As I said, I just need on and off and not programming or any other fancy features, so the cheapest option will suffice. Of course, the 'easiest' option would also be considered!

If I wish to have it checked out first, should I call the Gas Safe boiler guy or an electrician?

Thanks.

 

[ian1182]

Thanks ian1182. I have a few questions.

If it's wired, should I have the wires/connections checked first in case it's a wiring fault before purchasing a new unit? I probably won't be touching any wires myself but if I wanted to inspect it visually for any obvious loose connections, etc, do I just prise the front panel open with a screwdriver?

Why doesn't the heating work without the unit? I never use any programs anyway. Is it because it might also have a built in thermostat?

If it is wired, does that mean that any (or almost all) units would be compatible with the boiler? As I said, I just need on and off and not programming or any other fancy features, so the cheapest option will suffice. Of course, the 'easiest' option would also be considered!

If I wish to have it checked out first, should I call the Gas Safe boiler guy or an electrician?

Thanks.

Whilst the wiring could be a faulty it's unlikely in your case. As it's a battery powered model the display would be visible even if the boiler itself had no power. You can indeed prise the thermostat off the wall following the instructions from the install guide

Installation; Thermostat Wiring (Hard Wired Model Only) - Danfoss TP4000 Range Installation Manual [Page 5]

Danfoss TP4000 Range Manual Online: installation, Thermostat Wiring (Hard Wired Model Only). · First, Remove The Wallplate From The Back Of The Unit. · From The Top Left Hand Corner Of The Wallplate, There Must Be Clearances Of At Least 150Mm To The Right, 15Mm To The Left, 30Mm Above...

www.manualslib.com

Note you should power off the boiler at it's fused spur prior to disconnecting the thermostat.

"Why doesn't the heating work without the unit?"
In principle the thermostat is simply an on/off switch that tells the boiler to fire up, if the switch is faulty the boiler won't run

As you seem rather uncertain on the steps the easiest step might just be to get a heating engineer in. They would be able to replace the thermostat for you. Unless you have a timer on the boiler it would be prudent to ensure any replacement thermostat can have programmed times as well as temperature settings.

 

[Traveller]

In approximately 20 years of having a programmable heating control, I have never set any programs, however, I now realise that one day I may eventually need to be away from home and if it's winter time, might be a good thing to have to prevent pipes from freezing/bursting, so you do have a good point.

I will post an update when the unit has been looked at.

Thanks for the helpful info.

Sorry, your comment of the display being independent of wiring/cables slipped my mind, so I suppose I don't really need to have the unit looked at.

 

[Traveller]

I managed to open the unit (see the photos). The yellow 'X' in one of the photos is to highlight a copper wire that isn't connected to anything in the unit.

Before I go spending any money on things, is it easy/possible to have a system without any thermostats of any kind, that is, if I want to turn a radiator on heat setting 3, I want the radiator to stay that hot, until I turn it up or down and not for it to automatically go hotter or colder to try to maintain a constant room temperature?

I am assuming the current radiators have thermostatic valves (see photo) and am also assuming there is a main thermostat radiator which has different smaller valves (see 'left' and 'right' valve photos for the valve on the left and right side of this radiator).

Thanks.

 

[ian1182]

You need a thermostat and/or timer otherwise there is nothing to tell the boiler to stop. The TRV closes when the individual radiator is up to temperature but does not control the boiler in any way.

The X wire you highlighted is a earth which is not required, so it can be happily ignored.

As you can see there are only two wires to connect at the thermostat. Assuming you have a few tools it's fairly simple to take out the old and install a new.

You should allow £80-£100 for the programmable battery powered thermostat and probably that again if someone fits it for you.

 

[Traveller]

Thanks for your reply. Unfortunately, even after over 20 years of having a thermostatic system, I have never quite fully understood how it all works. There are temperature settings on the boiler itself, a thermostat controller like the one in this thread and also a round dial in the hallway. Why so many settings? All very confusing!

otherwise there is nothing to tell the boiler to stop.

The thermostat programmer on the wall has always been left on the 'always on' setting, permanently. Does the boiler still 'stop' with this setting?

As you can tell from my question about having a non-thermostatic system, I prefer everything to be able to get very hot and instantly! I have, however, come across the following comments from customer reviews of a product and am worried. How do I find a thermostat programmer that doesn't have this problem?

"Don't expect the radiators to get red hot as the thermostat gives short bursts of heat to maintain an even temperature"

or

"I expect a thermostat to call for heat until the set point is reached then shut off. Not so with this device. As soon as it gets to 1.5 degrees of the set point it shuts off for between 1 and 5 minutes"

I CAN'T have the above problems!

I think I may be able to fit it myself, however, there is no chance that the cables going into the unit are from anywhere else other than the boiler, is there? That is, switching the boiler off at the wall would cut out all power to the cables to the unit, correct? I wish to avoid paying £80 for a job easier than wiring a three-pin plug, however, I also would prefer not to be flying across the room!

Any opinions on the following?

Honeywell Home T4 1-Channel Wired Programmable Thermostat - Screwfix

Order online at Screwfix.com. Simplifies temperature scheduling, offering a high level of usability and automated control. Intuitive screen interface offers easy and optimal heating adjustment. Automated modulation control improves energy efficiency and optimisation features learn how the room...

www.screwfix.com

Thanks.

 

[ian1182]

"I prefer everything to be able to get very hot and instantly!" , not in this universe. It takes a while (15-60 minutes) for the water circulating in the radiators to warm the room. How long do you allow your kettle to run for a cup of tea?

I recommend you view some of the excellent central heating videos from John Ward on how the systems work.

As for the "I CAN'T have the above problems!" , I think you will find that's the way it works.

 

[Traveller]

Thanks for your reply.

Sorry, I wasn't very clear. I meant when I turn up an individual radiator, I like it to get hot straight away. Sometimes, it doesn't even start to get hot until a while. I didn't mean the temperature of the room.

Thanks for the video recommendation, that should really help.

I thought those were just issues that customers experienced with their particular product. If it's with all of them, I think I might just go for the item linked to above.

Thanks.