Vaillant ecotec plus 831 boiler broblem

[stevecase51]

A couple of months ago I had a Vaillant ecotec plus 831 combo boiler installed with a Vaillant VRT 350f programmable wireless room thermostat. Everything seemed to work OK on installation. The hot water works really well without any problems. With the rather colder weather recently, I have started to use the heating properly for the first time. When the room stat asks for heat, the boiler appears to go through the following sequence: (1) pump starts (2) burner fires and shows maximum on the left hand graphical display for a second or two, but then (3) drops to a low value and stays there. The flow temperature creeps up very slowly to the target value which I set to 65 degrees. Because the burner stays low, the radiators take ages to get up to 65 degrees. I should also mention that I have set the desired temperature on the controller several degrees above the room temperature to make sure this isn't having an influence.

I would have expected the burner to remain on full (or at a reasonably high level) and only modulate when the flow temperature approaches the target value. Installer can't come out for a few days. I would be very grateful if anybody with experience of this boiler/controller combination can suggest what the problem might be.

 

[newcastle phill]

Well many radiators never get to 70 degrees these days by designed giving a lower temp over a larger radiator surface area - its more efficient that way.

 

[stevecase51]

Nobody has suggested this yet, but could my slow warm-up problem be caused by the radiators not beiing balanced with a sufficient temperature drop, so the flow/return differential at the boiler is only a few degrees? Could this cause the boiler to restrict the burner?

 

[Rabbitman]

Nobody has suggested this yet, but could my slow warm-up problem be caused by the radiators not beiing balanced with a sufficient temperature drop, so the flow/return differential at the boiler is only a few degrees? Could this cause the boiler to restrict the burner?

Hi see my post no 7 poor circulation through the system could be a reason the radiators heat up slowly as the ntc's need to see the correct delta T, confirmed in d codes with the appliance sat in s53/54............ But as said get the installer back to look as this type of fault is usually confirmed using the 4 button display

 

[stevecase51]

It could be a number of things, poor circulation through the system ntc's not reading correct temperature differential appliance sat in S53/54, the VRT not correctly set up or the most likely is D00 set to auto........... My money is on the latter

Well it turns out you made the right call.Vaillant engineer called today. (Incidentally I was impressed with Vaillant who texted me to remind me he was coming, and then he phoned me early this morning to say what time he would arrive) Anyway he changed D00 from "auto" to 15 kW. He said that in 80% of intallations the heating output needs to be manually set because "auto" (which is a relatively new feature) doesn't work too well. He also found that the internal bypass valve was set to near the minimum pressure, which may not have been helping, and so he set it higher. Hopefully I can now look forward to shorter warm-up times when the cold weather sets in.

 

[rucky75]

Hi just been reading through your post, did the vaillant engineer solve your problem with his auto to 15kw change, were your radiators heating up quicker. I'm having a similar problem with a newly installed ecotec plus 832. Will call the installer but would be great on an update. thankyou

 

[gmartine]

Hi just been reading through your post, did the vaillant engineer solve your problem with his auto to 15kw change, were your radiators heating up quicker. I'm having a similar problem with a newly installed ecotec plus 832. Will call the installer but would be great on an update. thankyou

You may get a response but the thread is a year old, chances are it's okay or he would've reposted.

 

[stevecase51]

Hi just been reading through your post, did the vaillant engineer solve your problem with his auto to 15kw change, were your radiators heating up quicker. I'm having a similar problem with a newly installed ecotec plus 832. Will call the installer but would be great on an update. thankyou

Yes he did Heating has worked well - hope you get yours sorted

 

[rucky75]

Yes It did get sorted The engineer said the "auto" output setting often does not work well but seting D0 to 15kW was the answer

Thankyou for your reply, we are having exactly the same issue, heating taking 1/2 or more to get to the flow rate temp. Hot water fine, Installer is coming round next week, will mention your solution and take it from there. Again thanks

 

[ccarmock]

I have the same problem with an Ecotec plus 831 - . Was the fix setting D0 to 15 kW only or did you need more doing?

 

[rucky75]

I have the same problem with an Ecotec plus 831 - . Was the fix setting D0 to 15 kW only or did you need more doing?

Hi i lowered the DO down to 15, did'nt do anything else. Seem to solve problem. Scott

 

[MatthewHurt]

The VRT350F is a compensating control that will modulate the burner to achieve maximum efficiency during central heating operation. That does not mean that it will run full pelt, it may well run at minimum for an hour and should allow a very gradual heat up of the home, rather than running as a 'dum switch' which is either on 100% or off.
Adjusting the max heat load down to a fixed number just means that you've hindered the boilers ability to modulate and have effectively disconnected the main feature of your thermostat.
The D0 being set to auto is also a compensating feature, it means that you are able to use an old fashioned on/off thermostat, but set the boiler to modulate according to system demand.
It would be far more sensible to leave the boiler stat to do what it's built to do, and is often much cheaper to allow the boiler an extra hour or two to heat the house up by running at a very low rate, but if you're finding it takes far too long to heat the house then rather than setting D0 to a fixed number, you should adjust the heat curve of the controller (if a compensating control is fitted) to increase the boiler flow temperatures in relation to the given room temperature.