Help With Vaillant Boiler Spec

[nordberg73]

Hi,

I'm just researching Vaillant boilers and struggling a bit with the specification.. Can anyone tell me the basic difference between the ecoTec Pro and Plus range? As far as I can tell, it's pretty much flow rate (not withstanding the various BTU output of each model).

Which leads me to my second question; We want to run a thermostatic shower off our boiler, what flow rate would be necessary? I ask as my missus spends forever in the shower (by herself ) and I want to be sure that a the shower is powerful enough and, b she can have her shower sojourns without making the radiators go cold in winter!!

Many Thanks...

 

[Agile]

All combi boiler only supply EITHER CH or DHW but not both at the same time!

Usually for 20 minutes no one notices as the radiators have a considerable amount of heat stored in them when hot.

Tony

 

[nordberg73]

Thanks.

What about the flow rate? What would be a realstic flow rate for a shower off a combi?

 

[DP]

Bigger the power i.e. 24, 28. 31, 36, greater the amount of hot water the boiler will supply.

Difference between pro and plus is slight. One is made with minor items lacking, other comes with a full spec.

 

[D_Hailsham]

Bigger the power i.e. 24, 28, 31, 36, greater the amount of hot water the boiler will supply.

Assuming you have the necessary cold water flow rate in the first place.

A 24kW boiler will raise the temperature of a 10 litre/min flow by 34°C. If you have a 36kW boiler it could raise the temp by 51°C for the same flow rate. What the larger boiler cannot do is magically increase the hot water delivery flow rate from 10 to 15 litre/min.

 

[nordberg73]

Bigger the power i.e. 24, 28, 31, 36, greater the amount of hot water the boiler will supply.

Assuming you have the necessary cold water flow rate in the first place.

A 24kW boiler will raise the temperature of a 10 litre/min flow by 34°C. If you have a 36kW boiler it could raise the temp by 51°C for the same flow rate. What the larger boiler cannot do is magically increase the hot water delivery flow rate from 10 to 15 litre/min.

Thanks. That's useful info. I'm advised that we have "excellent" mains pressure...

 

[D_Hailsham]

I'm advised that we have "excellent" mains pressure...

Pressure and flow rate are not the same thing.

You can check your flow rate by using a bucket with litre marks and a watch. The kitchen tap should be used as that should come straight off the mains.

If you also have a garden tap off the mains, check the kitchen tap flow rate first with the garden tap closed and then with it fully open. The smaller the difference the better, as the second test mimics what will happen if two taps (hot or cold) are running at the same time.

 

[ianniann]

Generally anyone with half-decent mains pressure can have as much water through their shower as the combi boiler can heat. If not then the pipework to the shower is probably inappropriate. This means a perfectly adequate shower from the less powerful ones like a 24kW, up to near power-shower levels with the most powerful like a 42kW.

There's not a massive difference between the Ecotec plus and pro combis. 1 year standard warranty vs 2. The plus has a slightly more sophisticated pump, a slightly more sophisticated siphonic condensate discharge, an integral filling loop, a slightly flashier display panel, and maybe one or two other tweaks. The basic boilers are the same but the plus is available with higher power output.

 

[nordberg73]

OK -

I've worked out that I need 47000 btus to keep me warm. This, and the fact that we will be running a shower off the combi makes me think that an EcoTec Plus 831 would be preferable over the EcoTec Pro 28. Am I right?

 

[nordberg73]

Anyone?

 

[ianniann]

47,000 BTU is less than 14kW, so any combi will be far more powerful than you need. You might want to double-check with one of the many calculators produced this century that work directly in kW

To check what power you need for your shower, you will need to know the flow rate through the shower. This might be hard to determine if you currently have a different shower not run from a combi. A 28kW boiler is plenty powerful enough for an average shower, but if yours is something fancy that pushes through a lot of water then you might need the more powerful boiler. Note that getting a more powerful boiler will not necessarily give you a better shower, unless your mains pressure and installation allows higher flow rates.