Replace Danfoss 4033 with a Honeywell ST9400C Programmer

[kaycee81]

Hi guys

We've just bought a house that has a Danfoss 4033 timer for the heating & hot water, and it doesn't seem to be working correctly.

I'd like to replace it with a Honeywell ST9400C programmer.

Please could somebody advise on what connections go where, to change from one unit to another? I have attached a picture of our existing Danfoss controller.

From what I can gather, it's almost a straight swap, but I wanted to make sure -- there seems to be quite a few cables coming in!

Thanks in advance.

 

[rules&rulers]

http://heating.danfoss.com/PCMPDF/4033.pdf

Best to get a boiler tech to do the job and tidy up the wiring.

 

[stem]

Changing the wiring over between the two programmers is relatively straight forward, rules&rulers link above gives you the wiring for the 4033 which corresponds to the ST9400 as follows:

4033 Terminal 1 = HW Common (Not required by ST9400 as it makes this link internally)
4033 Terminal 2 = Heating ON = ST9400 Terminal 4
4033 Terminal 3 = Heating OFF = ST9400 Terminal 2
4033 Terminal 4 = Hot Water ON = ST9400 Terminal 3
4033 Terminal 5 = Hot Water OFF = ST9400 Terminal 1
4033 Terminal 6 = Live = ST9400 Live
4033 Terminal 7 = Neutral = ST9400 Neutral

However, there are wires presently connected to terminal 3 of the 4033, which is the 'heating off' terminal, I have never seen this connection used on any UK domestic heating installation, so I would suspect that your fault may not be with the programmer, but the wiring connected to it. If so, replacing the programmer may not rectify the problem.

Unfortunately, without knowing what is connected to the other end of each of the wires it is impossible to advise further, so engaging the services of a professional would could physically examine the installation, would probably be a good idea. The installation quality is poor, there is no means of securing the cables, and a green and yellow earth wire seems to have been used as a neutral connection!

There may also be some limitations caused by the plumbing of the system that inhibit the flexibility of the controls, some systems for example do not allow the heating to operate unless the hot water is also on.

 

[rules&rulers]

Best to get a boiler tech to do the job and tidy up the wiring.

Apart from exchanging the programmer other tests including preliminary and concluding electrical tests are necessary.

As stem has mentioned it appears the existing programmer wiring is incorrect,

There are HSE guidelines in relation to wiring and this programmer replacement would be classified as a modification.

so a job for a professional.

 

[kaycee81]

Thank you guys, I think this one is going to be one for a pro - I've been up in the loft where all the wiring leads to, there's a relay up there of some sort, connections to two pumps, and what looks like a thermostat cable running into the living room (to the room stat). Supposedly the boiler was upgraded 5 years ago by British Gas, and all of the programmer etc was changed. Do you think that I could contact them to highlight this? They probably wouldn't admit to it anyway! I wouldn't have expected workmanship like this from them!