Lessons learned from last ready - getting ready for cold snap

[sharpener]

I seem to have heard somewhere that with the Vaillant figures the yield does not include the input power so you need to divide it by the input power and then add 1 to get the CoP. Don't know if this is true or not.

[Blooda]

  On 12/12/2023 at 22:56, SuperJohnG said:

The Vaillant Arotherm unit doesn't give you the COP? it only provides info on energy yield as a total, then it gives power consumption for heating and DHW, but you can only figure out an overall COP not individual. 

 

My COP  was 2.74 last month. 1386kWh yield, 505 kWh power consumed. Seems like the COP isn't great. 

 

The WC I haven't messed with (largely as I don't know how) but it's fairly simple with no buffer, ASHP straight to the UFH which is a single zone. 

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The Cop [In Vaillant terms] for this would be  ---  (Yield+Consumed)/Consumed   ---    (1386+505)/505  = 3.74, which is not bad. 

I

 

[JohnMo]

 

  On 13/12/2023 at 08:15, Blooda said:

 

The Cop [In Vaillant terms] for this would be  ---  (Yield+Consumed)/Consumed   ---    (1386+505)/505  = 3.74, which is not bad. 

I

 

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So the yield is just the figure for what the heat pump is gaining and not the total, for energy given out. So a CoP of one, would be a yield of zero?

[Beelbeebub]

  On 13/12/2023 at 08:15, Blooda said:

 

The Cop [In Vaillant terms] for this would be  ---  (Yield+Consumed)/Consumed   ---    (1386+505)/505  = 3.74, which is not bad. 

I

 

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Or simply cop=yield+1

[Beelbeebub]

  On 13/12/2023 at 08:24, JohnMo said:

 

So the yield is just the figure for what the heat pump is gaining and not the total, for energy given out. So a CoP of one, would be a yield of zero?

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I think so.

My guess is that vailant are a boiler company so that thinking is sort of built in to how they view things, and the (electrical) energy consumed by a boiler is not really relevant to the final heat output.

[Blooda]

 

  On 13/12/2023 at 08:25, Beelbeebub said:

Or simply cop=yield+1

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CoP = [Yield/consumed] + 1 

 

 

[Beelbeebub]

  On 13/12/2023 at 11:19, Blooda said:

 

 

CoP = [Yield/consumed] + 1 

 

 

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Yes, too early in the morning!

[SuperJohnG]

  On 13/12/2023 at 08:15, Blooda said:

 

The Cop [In Vaillant terms] for this would be  ---  (Yield+Consumed)/Consumed   ---    (1386+505)/505  = 3.74, which is not bad. 

I

 

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Thanks for this...seems better at that. However that's a funny way they do it! 

[SuperJohnG]

Very helpful link for those with Arotherm units who want to understand COP figures 

 

https://energy-stats.uk/how-to-measure-vaillant-arotherm-cop/amp/

[eandg]

So using that metric our COP is 3.16 which doesn't seem great. Will that improve in the better weather when the temperature differential is less? Anything we can do to improve it?

[JohnMo]

  On 15/12/2023 at 11:20, eandg said:

So using that metric our COP is 3.16 which doesn't seem great. Will that improve in the better weather when the temperature differential is less? Anything we can do to improve it?

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How do you operate at the moment?

[eandg]

  On 15/12/2023 at 11:43, JohnMo said:

How do you operate at the moment?

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We've just left it as the installer set up. 7kW system, 50° water temperature. UFH on ground floor only set at 21°. 

[JohnMo]

  On 16/12/2023 at 07:50, eandg said:

50° water temperature.

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That's why you CoP isn't great, you need to start to reduce that flow temperature, ideally set up weather compensation.

 

Start by dropping the flow temp a couple of degrees leave for 24 hours and note down what if any has changed and outside average temp, keep doing this until the house temp drops a and doesn't recover back to 21, then add a degree back on.

 

Your flow temp will be more likely be in the mid 30s than 50.

[eandg]

  On 16/12/2023 at 08:34, JohnMo said:

That's why you CoP isn't great, you need to start to reduce that flow temperature, ideally set up weather compensation.

 

Start by dropping the flow temp a couple of degrees leave for 24 hours and note down what if any has changed and outside average temp, keep doing this until the house temp drops a and doesn't recover back to 21, then add a degree back on.

 

Your flow temp will be more likely be in the mid 30s than 50.

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Thanks - will do. 

[SuperJohnG]

  On 16/12/2023 at 07:50, eandg said:

We've just left it as the installer set up. 7kW system, 50° water temperature. UFH on ground floor only set at 21°. 

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Is that 50 degrees your DHW or UFH? 

 

I've got 52 degrees for DHW and UFH is on weather comp