Viessman 200, Combi, Warm Radiators when on HW service!!

[rizsher]

Got a Viessman 200w installed around middle of January, mostly because I thought I was getting atleast slightly better than an average product!.

Encountered first problem within a few weeks of installation and had to fight to get Viessman to come out and fix the issue (to be fair, once I ad elevated the issue, they were quite quick in sending an engineer out).

Starting about 2 weeks ago, the boiler started hanging on F4 error. Called Tech Support, they came the next day, looked at it, said it was a faulty temperature sensor, left to order it, came 4 days later to replace it, that was last Friday. After replacement, the F4 fault hasn't recurred... however, I noticed that even though we've got the boiler on DHW service only (the controller has 2 buttons, one to toggle DHW only. the other to have bot DHW on demand and Central Heating on timer), the radiators were getting warm... NOT hot, just warm to touch.

Not sure what is going on, but just now, the wife noticed the LCD display showed the C/H pump activated symbol had come on on the LCD, even though the DHW ONLY setting was also on on the boiler. Attaching a picture of the display whne it happened.

Any ideas why/how this is happening?. I first thoguht maybe the diverter valve was passing and sending "some" heat to the radiators... however, looking at the LCD now, its EITHER a "feature" of the boiler I hadn't noticed before, OR, the logic board or PCB or some other pinnacle of German tech inside the boiler has gone bonkers...

Appreciate any feedback...

See the image, the DHW ONLY setting (denoted by the tap) is lit, but the LCD shows the pump on the radiator is ON.

Untitled

• rizsher
• 5 Jul 2010
• 1

 

[mysteryman]

They are sent out from Germany with three default settings for pump overrun which you may wish to adjust.

Find the Service instructions, look for the section on Coding.

Visit Code level 2, find addresses F5, F6, and F7. Adjust all three to value 1 and confirm.

This reduces pump overrun to 1 minute after a central heating run, and gives the pump a ten minute exercise once per day when the boiler is set either to hot water only or to standby. Otherwise, the pump will run constantly in dhw or standby - this is what was happening in your case.

You have constant temperature control - things are different with weather compensation, and these adjustments do not apply.

 

[Agile]

Why do they send them out set like this?

What does the default setting set out to achieve apart from annoying the customer and getting the installer worried!

Tony

 

[Alfredo]

Why do they send them out set like this?

What does the default setting set out to achieve apart from annoying the customer and getting the installer worried!

Tony

That my friend is a very very good question.

My first intro to Viessmann was three or four years ago when our company took over the maintainance of a block with about 15 Vitodens 200 combis in, the installing company having gone under before finishing them all......Well apart from the long distance 15mm gas pipes supplying them the missing flues the incomplete and just poked out of the wall condensate pipes We came across the indecipherable Viessmann manuals.

We thought we had sorted them out..but we kept getting complaints about rads on with HW..and as the occupants were mainly people with learning difficulties we were guilty of poo-pooing them a bit, quite wrongly as it happens.

In our defence we were concentrating on getting them safe to use, but eventually we got on to Viessman technical who took us through this exercise.....which they called "Commissioning" to get rid of the pump on all the time.

I don't think we'd have got there in a 100 years of pressing buttons.....well we would, but it makes you wonder about the mindset that manufactures things this way.

Alfredo

 

[vulcancontinental]

They also have recalibrated the thermostat on the heat only models so the set point for normal use (80degC) is now significantly less. It just doesn't appear anywhere in the literature. Apologies if this is old news, it wasn't to me.

 

[mysteryman]

The maximum flow temperature is 74, so that with the standard German delta T of 20, the return will be just on condensing temperature. You can get a mod to give a flow of up to 80 on some versions.

I don't know why they are sent out with the pump on constant - you'd need to ask Technical in Germany. The rest of the Continent always fits weather comp, so the problem doesn't arise.

Try Technical on 01952 675070 for any help you need.

 

[vulcancontinental]

Noted, thank you.

 

[Agile]

I don't know why they are sent out with the pump on constant - you'd need to ask Technical in Germany. The rest of the Continent always fits weather comp, so the problem doesn't arise.

Try Technical on 01952 675070 for any help you need.

I appreciate that its not your fault and whilst you dont admit to working for them you seem to know a lot about them and you are also in Telford!

I have been to their ARGI days and I dont remember that very useful point being mentioned ! Was I asleep? John did not wake me up!

But I did encounter the problem myself with an over active customer and it took me a lot of persuasion to make him realise that its summer and he does not need heating on and when I fit the always delivered later comp unit it will be sorted!

Tony