Vaillant ecotech 831 - Not up to the job?

[goon3r]

Just fitted a ecotech 831. Had high hopes switching from a conventional system (fuelsaver 65F). Now upstairs is hot and as we wanted but downstairs wont heat up. return pipes cold. flow warm. if i switch off all rads upstairs then downstairs will get luke warm but not really hot???

Been told there is a circulation problem its been powerflushed and pH checked - was fine, all old steel rads changed to modern ones with convectors.

Didnt have an upstairs downstairs issue on old system so not sure if circulation or boiler not up to job?

Any ideas guys?

3 bed house, 1 bathroom, 10 rads.

 

[Biggles..]

You need to balance the system have a look in the FAQ section

 

[goon3r]

I thought that only applied if the rads closest to the boiler were warmer. The reverse is true. my boiler is downstairs. The rads furthest away are the upstairs ones which work fine

 

[Biggles..]

It works on pipe size feeding them,the resistence of the rad,the flow of water etc.

Turn all off and start to balance as the FAQ suggests,if your system ha had a pf then it can't be dirt and the boiler is more than capable of doing
10 average sized radiators.

The only other question is has the boiler been downrated too low for your need,read the instructions ref d0 for this info,the figure should be set to the requirement for your house which you can get from one of the heat calc websites

 

[D_Hailsham]

The boiler is more than adequate for that size house.

You have replaced a 19kW boiler with a 24kW one; why?

Was the CH requirement taken into consideration when sizing the boiler?

Are the new rads the same output as the old ones or did you take the opportunity to put in larger rads?

Did the installer range rate the boiler to give the correct CH output? Its the d.0 setting.

Did the installer make sure that the pipe sizes were OK if larger rads were installed?

Do you have thermostatic valves on the rads?

Did the installer balance the system?

 

[Biggles..]

I would have though the installer based his choice on a) the existing boilers output and b) the customers hot water demand and found that the 831 is the best choice to satisfy both, which in my opinion in 95/100 times fo that size house and hot water demand is the case.

All the rest seem that the fine tuning at the end of he job haven't
been carried out(balancing,rating etc)

 

[Tibbot]

Just fitted a ecotech 831. Had high hopes switching from a conventional system (fuelsaver 65F). Now upstairs is hot and as we wanted but downstairs wont heat up. return pipes cold. flow warm. if i switch off all rads upstairs then downstairs will get luke warm but not really hot???

Been told there is a circulation problem its been powerflushed and pH checked - was fine, all old steel rads changed to modern ones with convectors.

Didnt have an upstairs downstairs issue on old system so not sure if circulation or boiler not up to job?

Any ideas guys?

3 bed house, 1 bathroom, 10 rads.

You describe a scene of installation incompetence and entitle your post as boiler not up to job?

 

[landyandy]

Who fitted and commissioned the system

Andy

 

[goon3r]

Ok - gonna try and answer all feedback.... D_Hailsham... I changed as i wanted combi - i have excellent mains water pressure, want hot water on demand and to free up space where tanks and previous boiler was fitted. Also benefit of upgrading a G rated boiler fitted in 1989 to A rated condense.

I put larger rads everywhere. So previously i had the old steel type rads now i have convectors. TRV's fitted on all. Found out it was balanced when the issue first came about.

The gas supply feeding boiler was upgraded from 15mm to 22mm.

So i guess from remaining feedback all that remains is to check the rating or commisioning of the boiler?

until recitfied i guess i have very hot upstairs, excellent shower and freezing cold downstairs

 

[Biggles..]

It's deffinately not balanced or the powerflush wasn't done correctly if you have cold downstairs rads.

 

[sambotc]

Read the vaillant manual, rating is not required as boiler is fully modulating depending on demand. I've got an 831 in my house and rated down to 19kw just for the hell of it but can confirm it made F all differance to performance or fuel bill.

Untitled

• sambotc
• 7 Mar 2010
• 1

824 doesn't have the best HW output at 9.2 ltrs/min so can see why installer's choice was 831.

Sam

 

[mickyg]

wheres the installer???

 

[barryauid]

Are the downstairs rads drop fed?

 

[D_Hailsham]

I changed as i wanted combi

OK. But CH requirement seems to have been ignored.

I put larger rads everywhere. So previously i had the old steel type rads now i have convectors.

Was the CH output of the boiler taken into account when sizing the new rads?

TRV's fitted on all.

Do you mean all? Or does one rad have a plain valve and there is a wall thermostat in the same room?

Found out it was balanced when the issue first came about.

Do you mean that the installer says that he balanced the system?

So i guess from remaining feedback all that remains is to check the rating ... of the boiler? Until rectified i guess i have very hot upstairs, excellent shower and freezing cold downstairs

Is the boiler cycling all the time - starting up, running for a few minutes, shutting down, wait a few minutes and then restart the sequence?

If so, rating the boiler will help. What is happening is that the boiler is producing more heat than the rads can handle when the boiler starts up. This is because the boiler always starts at full output and does not modulate down fast enough before the boiler thermostat turns it off.

I suggest you do two things:

1. Check your CH requirement using either EST online boiler calculator or Energy Savings Trust Grant Search. You must deduct 2kW from the result to get the CH requirement.

2. Add up all your radiator outputs - you should have this info as they are new rads.

The boiler CH output should be set to the figure determined by item 1.

It does not matter if the total rad output is larger than the CH requirement. It just means the rads will be able to run at a lower temperature, which is more efficient.

 

[Boilerman2]

Why are people pointing to the boiler, when the fault is clearly a CIRCULATION/BALNCING ISSUE