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Air Source Heat Pumps (ASHPs)
Last Post by JamesPa 3 hours ago
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 JamesPa
(@jamespa)
Illustrious Member Moderator
Joined: 2 years ago
Posts: 2399
04/05/2025 2:36 pm  

Posted by: @johnmo
↑

Posted by: @harryrea
↑

So, rather than viewing zoning purely as a matter of room-level control or motorisnised valves, I’m interested in how zones can be used as structural tools — to segment a system into independently operating hydraulic circuits. That way, each zone isn’t just passively reacting to room temperature but is set up to allow the appliance to operate efficiently and predictably.

Isn't this making an issue way more complex than it ever needs to be - overthinking it? A system running low flow temperature and emitter sized to room, balancing is easy and to a large degree self modulating - even a radiator system can be designed to flow low temperature.

I agree (that it's overthinking).

I think people forget that rooms share heat and houses have significant heat capacity.  So in many, perhaps most, cases, balancing of rooms only needs to be very approximate (I was quite shocked how easy my house was to balance even with rads running at 42), solar gain in one room distributes to others so matters less than one might fear, and the kind of arbitrary variation of individual room temperatures with time that people (and the manufacturers of smart controls) fantasize about is just that, a fantasy.

As it happens I think that what  @harryrea is studying may well turn up some interesting and useful findings 'as an aside' (which is why I encourage him to post some specific details of results).  However I am personally sceptical about it's direct practical impact and remain convinced that KISS is the likely winner for domestic buildings.

This post was modified 5 hours ago by JamesPa
This post was modified 4 hours ago 5 times by JamesPa

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.


   
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 Johnmo
(@johnmo)
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Joined: 2 years ago
Posts: 433
04/05/2025 3:38 pm  

Posted by: @harryrea
↑

or hybrid systems

Do you even need the complexity there either. I have run my system in hybrid mode, with gas condensing boiler and heat pump. I do hydraulically separate the boiler, but just via a simple, but big plate exchanger. I just dialed in a flow temperature where the boiler would fire and run none stops for as long as I wanted it to. So can run for around 7 to 8 hours at minimum modulation (8kW against a heat demand of about 3kW) without stopping. Heat just buffering into the floor. When it switches off, it stays off, for about 12 to 18 hours. Flow temp is about 36 degs, return is close to 32. Works well. It's also used with the ASHP for DHW cylinder heating, max flow temp is generally 56 degs and cylinder settles at 53 degs. So almost no temperature is lost across the big plate exchanger and little or no distortion of either system. Heat pump can be run either in weather compensation mode or batch heat mode buffering heat to floor, system doesn't really care.

I did think about using an ERG zone, but it really added little except more pumps and costs.

So a full hybrid system is 2x pumps, heat pump one runs 24/7, boiler only as needed. One PHE, one controller for boiler using room sensor and outside temp, fires boiler when outside is below 5 degs for 6 hours or more. Zero interactions between each heat source, they operate without talking to each other via any means. A relay sends DHW call for heat to both boiler and heat pump at same time.

Maxa i32V5 6kW ASHP (heat and cooling)
6.5kW PV
13.5kW GivEnergy AIO Battery.


   
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 JamesPa
(@jamespa)
Illustrious Member Moderator
Joined: 2 years ago
Posts: 2399
04/05/2025 3:55 pm  

Posted by: @johnmo
↑

Do you even need the complexity there either.

Hang on a moment, Honeywell, Johnson controls, Google, hive etc depends on selling us stuff we don't need. If you carry like this they will go out of business!

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.


   
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