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My Mitsubishi ASHP has used 1078kWh from 25 November to 31 December – Help please

 
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Air Source Heat Pumps (ASHPs)
Last Post by Sarah 3 years ago
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SUNandAIR
 SUNandAIR
(@sunandair)
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Joined: 3 years ago
Posts: 508
16/03/2023 11:14 am  

Posted by: @harriup
↑

At the bottom of page 6 it states the water flow rate range is 10.0 to 24.8 l/m. Similar to mine, though I have also seen the tank installation manual be a bit more specific that the flow rate should be 24l/m. Not sure what to make of that difference. There is discussion in other threads about altering the flow rate to manage the difference between flow and return temperatures to 5°C, but if the manifold temps of 28 and 21 are typical then you have a slightly too large difference, which is to be expected if the flow rate is lower than it is meant to be.

Hi @Harriup

i thought I ought to add some comments on this for Sarah to consider.

Theres a good reason why there is a flow rate range quoted, and probably other reasons too. 
It was generally believed in an earlier thread (Keystone COP) that Ecodan does not have an internal pump to regulate deltaT so there are 2 things that can control it. 1. Adjusting the flow rate via the circulation pump of the primary flow and primary return and 2. The internal modulating electronics which cannot regulate the circulating pump. In other words the ecodan operates at a constant flow rate depending on the chosen set pump speed.

A flow rate must therefore be measured on the return primary pipe since that is precisely en-route back to the heat pump and will give a near accurate measurement of flow through the heat exchanger. (I would say it’s essential to check this before any adjustment of flow rate)

another thing to point out is that a 28 to 21 differential is only 7c which is quite common when the hp is still settling down. I’ve noticed it fluctuates all the time between 3c and 8c and when it starts up it can be more. 

So a flow rate of 13LPM is within the acceptable band of the ecodan 8.5 provided it is being measured in the correct place in the circuit. But if the temperature difference never settles close to 5c then a slightly faster pump speed will lower the temperature difference. However there are other issues such as balancing flow rates between the primary loop and other heating circuits so this kind of adjustment really needs to be done by a professional. 
Hope this helps



   
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 Sarah
(@sarah)
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Joined: 3 years ago
Posts: 79
Topic starter 16/03/2023 7:30 pm  

@sunandair hi - yes that does help and again makes sense that it's set by the gauge on the pump itself - i.e. that is the maximum it will flow.  I've had a manic week this week - but I need to look at the manifold on a regular basis for the living area to see what the return is.  The thermostat is set to 18 for the living area - but rarely gets to that, unless there is solar gain - for the past two days it is still 17 degrees at 18:00 - when it was 16 degrees at 09:00.  In all honesty this could be what I have to live with and it doesn't feel cold.  The other 2 zones always get up to their set temp - although their set temps are 16 (bathroom area) and 17(bedroom area).    Everything generally is SO MUCH BETTER since I first found this forum 🙂



   
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