Efficient heating of DHW cylinder with Vaillant ecoTEC

[UpgradeME]

It's also worth bearing in mind that each tank reheat takes 4kWh that could cost you as little as 20p depending on your gas cost. If you save 10% then that's 4p per day for two reheats. At the end of the year you can all go out and have a MacDonalds to celebrate, but that's about all.

Okay, a quick look at the gas prices in my spreadsheet reveals if I lowered by usage back to the old boiler's levels (-20%), I would save £16 over the summer.... so could perhaps even afford a McFlurry as well for the kids!!

Seriously, I guess I was looking too much at percentages and forgetting the underlying value!

Still don't understand why this is using 20% more fuel than my old boiler but think I'll use my time more productively and just tweak for comfort levels rather than chasing a McDonalds meal!

Thanks everyone for their advice above, I've now learn't a little bit more!! -8)

 

[Agile]

See what I have added to my last posting !

I do have to admit I like to chase the last % of efficiency at home.

But I dont like McDonalds ( apart from their hot apple pies, now £1.29 for two).

 

[dumbrill]

But he could have TWO of the McDonalds if he insulates his pipes!

What about his cholestrol?

 

[UpgradeME]

I would also tentatively suggest you try the effect of increasing the delta on the flow valve. Thats assuming you have an auto bypass valve.

Yes, I do.

Regarding the boiler power, I now think that about 6-9 kW may be more appropriate for your needs. The purpose is to have it low enough to prevent/reduce the boiler cycling off.

I'm now getting 12C delta (with cylinder valve half closed) on d.40/41 until the flow temperature reaches 70C, the boiler then modulates down and so does the delta. Using the formula Flow (l/min) = Power (kW) ÷ 4.1 (kJ/l/K) * 60 (s/min) ÷ ΔT (K) gives me a flow rate of 12.19 l/min. If I then modify the formula ΔT (K) = power (kW) ÷ flow (l/min) ÷ 4.1 (kJ/l/K) × 60 (s/min) I can work out that the boiler is modulating down to approx 6-7kW.

You can calculate the power adsorption by having the boiler stably heating the water and measuring the gas rate at the meter ( see FAQ )

I've just checked the FAQ and couldn't find it? Could you provide a link?

 

[Agile]

Look at No 6 here which is listed as just "FAQ" on the list of topics.

//www.diynot.com/forums/viewtopic.php?t=37170