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ASPH Sizing Confusion

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(@derek-m)
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@jamespa

We are indeed in full agreement.

If my understanding is correct, Heat Geek was referring to balancing the flow around the system, such that the thermal energy supplied by the heat emitters in a given room, would match the heat loss of that room at the desired IAT.

This post was modified 9 months ago by Derek M

   
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(@jamespa)
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Posted by: @derek-m

If my understanding is correct, Heat Geek was referring to balancing the flow around the system, such that the thermal energy supplied by the heat emitters in a given room, would match the heat loss of that room at the desired IAT.

Yes mine also.  It seems a sensible approach to me, much more sensible than making DT across each emitter the same in a system where the aim is to operate open loop or thereabouts.

 

I am hoping someone comes up with a trv that does this automatically, it needs a long time constant and perhaps a bit of intelligence which mechanical trv actuators don't have, but electronic trv actuators could have.  Or of course some other simple mechanism to tackle this complicated to do process.  

 

Of course we don't yet know what 'octopods' featured in octopus energy's recent announcement, do!

This post was modified 9 months ago by JamesPa

   
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(@sunandair)
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Posted by: @derek-m

Performing calculations on the data obtained-

Test 1.

Specific Heating Capacity of water x volume of water (lpm) x Delta T x number of minutes = 1.16 x 13 x 7 x 36 = 3800Wh

Test 2.

Specific Heating Capacity of water x volume of water (lpm) x Delta T x number of minutes = 1.16 x 20 x 3 x 52 = 3619Wh

Specific Heating Capacity of water x volume of water (lpm) x Delta T x number of minutes = 1.16 x 20 x 4 x 52 = 4825Wh

So it would appear that during both tests, the quantity of thermal energy transferred from the heat pump to the DHW cylinder, was in the region of 4kWh, which would equate to a temperature rise in the order of 16C.

It occurs to me there may or may not be differences in efficiencies between the two heating cycles. However I’m also thinking that there are other benefits from a faster DHW cycle which may benefit from a closer look : What springs to mind with your calcs is that the second graph reheat cycle takes 44% longer - that is 44% longer for each and every DHW Cycle. And as we know the cop of DHW Heating is approx. COP2. Whereas the quicker reheat would allow the HPsystem to revert to room heating quicker for comfort reward as well as returning to a COP3.7 or 4 sooner.


   
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(@sunandair)
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Posted by: @sunandair

We have altered our system so we now have removed the LLH, removed the second pump and checked out all pipe sizes and junctions. I’ve also had a flow setter fitted but probably won’t  be necessary. This has given us control of flow rates without the hazard of mixing temperatures which would have happened through the Low loss header as it was originally set up.

After copious sketches and discussion our installer did all this alteration completely Free of charge so there is a lot to be said for healthy relationship with your installer - and frank knowledgeable discussion.

We even got a slightly bigger 8m head pump since the new single circuit needed to cope with both the Primary Circuit and the heating circuit.

 

 

 

Have you noticed any differences since the alterations were completed?

all the signs are great at fixed flow temp setting however we don’t need heating yet.

It’s too early to consider auto adaptive or WC as we have got an outdoor ambient of 17c and an unheated internal room temp already at 22c in the main living space. But all the signs and pump range, emitter capacity etc are looking good. Our emitter capacity is 13.17kwh based on t35degC. With a HP rated at 8.5kwh.

Looking forward to colder weather 🤣🤣🤣


   
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(@derek-m)
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Posted by: @sunandair

Posted by: @derek-m

Performing calculations on the data obtained-

Test 1.

Specific Heating Capacity of water x volume of water (lpm) x Delta T x number of minutes = 1.16 x 13 x 7 x 36 = 3800Wh

Test 2.

Specific Heating Capacity of water x volume of water (lpm) x Delta T x number of minutes = 1.16 x 20 x 3 x 52 = 3619Wh

Specific Heating Capacity of water x volume of water (lpm) x Delta T x number of minutes = 1.16 x 20 x 4 x 52 = 4825Wh

So it would appear that during both tests, the quantity of thermal energy transferred from the heat pump to the DHW cylinder, was in the region of 4kWh, which would equate to a temperature rise in the order of 16C.

It occurs to me there may or may not be differences in efficiencies between the two heating cycles. However I’m also thinking that there are other benefits from a faster DHW cycle which may benefit from a closer look : What springs to mind with your calcs is that the second graph reheat cycle takes 44% longer - that is 44% longer for each and every DHW Cycle. And as we know the cop of DHW Heating is approx. COP2. Whereas the quicker reheat would allow the HPsystem to revert to room heating quicker for comfort reward as well as returning to a COP3.7 or 4 sooner.

My point was that both methods appear to provide approximately the same quantity of thermal energy, and I would not like to speculate which, if any, is the most efficient method. Faster heating would probably entail the heat pump operating at lower efficiency, whilst slower heating could possibly cause a lower IAT, which would require additional thermal energy to recover.

Oh, the joys of heating systems. 😎 

 


   
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(@fazel)
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@bontwoody did you size it right? last 8-9 days, zero cycling.

image

   
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(@bontwoody)
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Posts: 418
 

@fazel Hi, Ive been playing around with the WC Curve. Currently set to 38C @ 17C OT and 45C @ -2C OT. I havent had a cold enough day yet to test the lower end but things are nice and cosy in the house now (22C in living room). I was worried that doing this might have wrecked my COP but it seems to have made very little difference as last nights graph shows. I havent seen any cycling yet with these settings.

image

House-2 bed partial stone bungalow, 5kW Samsung Gen 6 ASHP (Self install)
6.9 kWp of PV
5kWh DC coupled battery
Blog: https://thegreeningofrosecottage.weebly.com/
Heatpump Stats: http://heatpumpmonitor.org/system/view?id=60


   
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(@bontwoody)
Noble Member Contributor
2943 kWhs
Joined: 2 years ago
Posts: 418
 

@fazel LOL, Ive just noticed you were posting my heatpump graph! I thought it was yours :-). I think the slightly colder weather has helped my heat pump as its not running at such a low capacity now.

House-2 bed partial stone bungalow, 5kW Samsung Gen 6 ASHP (Self install)
6.9 kWp of PV
5kWh DC coupled battery
Blog: https://thegreeningofrosecottage.weebly.com/
Heatpump Stats: http://heatpumpmonitor.org/system/view?id=60


   
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(@derek-m)
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Posted by: @bontwoody

@fazel Hi, Ive been playing around with the WC Curve. Currently set to 38C @ 17C OT and 45C @ -2C OT. I havent had a cold enough day yet to test the lower end but things are nice and cosy in the house now (22C in living room). I was worried that doing this might have wrecked my COP but it seems to have made very little difference as last nights graph shows. I havent seen any cycling yet with these settings.

image

Why is the IAT always missing from the graphs?

 


   
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(@bontwoody)
Noble Member Contributor
2943 kWhs
Joined: 2 years ago
Posts: 418
 

@derek-m well I don’t have an internal temperature probe attached to my monitoring system but I suspect because it might be different in different rooms. I know mine is.

House-2 bed partial stone bungalow, 5kW Samsung Gen 6 ASHP (Self install)
6.9 kWp of PV
5kWh DC coupled battery
Blog: https://thegreeningofrosecottage.weebly.com/
Heatpump Stats: http://heatpumpmonitor.org/system/view?id=60


   
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