What size boiler

[Phill Peck]

Its the Ecomax 828/2e.
Have had nothing but problems. PRV has been changed twice. Gauge always shows at zero. The small heat exchanger has just failed, water spraying everywhere. Have been told the fan has gone due to the spraying.
Have now discovered the guys who installed it have not followed guidelines. PRV pipe goes up. Gas pipe connection is app illegal. Its just been a nightmare.

Ok fair enough I can understand that if you've had a major leak inside it could be time to replace it. Although it sounds totally repairable.

Sounds as though you have some issues with the system though. A prv doesn't fail on its own. The system pressure would have to rise and also be very dirty for the prv to not seal again

 

[Phill Peck]

Is the cycling just a cost issue or does it damage the boiler too?

If its set up correctly it won't cycle anyway

Yes the theory is it is bad for the boiler, each component with have a "cycle life" every time the boiler starts and stops (cycling) it wears components eg ignition units, fans etc

 

[JessieJames]

Your prob right but Ive lost faith with it now. I just cant be sure what else these cowboys might have done wrong. I had checked them out. Were Corgi registered. Surprise surprise they are not trading now.

 

[JessieJames]

Looking at the Worcester 34CDI. Is that overkill?

 

[ServiceNumpty]

The installer should range rate the heating on the WB Cdi, they do a smaller 29cdi with a 30kw output for hot water, dhw flow rate around 12lpm. I've fitted 34cdi & 38cdi in your size house. It's all dependent upon cold water flow rate and hot water requirements fro the household.

 

[JessieJames]

Thanks. He is also mentioning the 36CDI compact. Fairly new model im told. Any thoughts?

 

[Dan Robinson]

Stick with the older CDi for now.

The ecoMax wasn't vaillant finest hour IMHO

cycling will be inevitable with 9 rads and a combi. Concentrate on your hot water needs.

Range rating will only do so much as there is only so low a boiler can run at - members of the CC will know I am experimenting with this at home with mixed success.

 

[JessieJames]

What is range rating? is it limiting the output?

 

[Dan Robinson]

Yes.

But if you have a heat loss of 8kW and a boiler that has a minimum output of 9kW there is not much point .

You only need the calculated heatloss of your property for 2 weeks a year, the rest of the time you only need a fraction of that.

Like i said though... if you're having a combi - concentrate on the hot water.


Mind you.

We have an Vaillant 824 fitted to a customers garden games room. One shower 2 rads. Poor thing is suffering. Which is why i no longer listen to architects when they specify projects.

 

[JessieJames]

So am I understanding this correctly?
Having a higher output boiler is more down to the hot water. Even tho its output will be scaled down it needs to be higher for the water?

 

[Dan Robinson]

Yes.

Combi heat the water instantly so need much more gas for that job.

24kW = 9 litres per minute

28kW = 11

35kW = 14


ROUGHLY before the pedants kick in - my dinner is cooking

This is raising the water 25 degrees and not to a fixed 60 degrees that you might be used to.

Heating is a fraction of this.

Limitations of technology and cost benefit ratios means that they can only make boilers with a limited range of max and min.

Intergas for example go down to 7kW.

Range rating just means the boiler won't ramp up to full tilt - which will result in a shorter initial burn.

If you're unlucky cycling can be an issue in that the boiler fires up, builds up to full tilt and shuts down on its flow sensor before the rads start getting hot. This keeps happening meaning the heating never really gets going.

Range rating helps minimise this problem. but doesn't actually cure the long term cycling issue.

 

[JessieJames]

So if it does start cycling, what are the options?

 

[Dan Robinson]

Open a window.

 

[JessieJames]

Lol. But doesn't it mean the opposite, the rads wont get up to the required heat because the boiler is throttling back?

 

[Dan Robinson]

Indeed.

You set the rating as close to the property's requirements as possible.

There's nothing more that you can do.