Discussion on buffer tanks and heat pumps
Now my install has been plumbed correctly I've turned my attention to the buffer, backup heater and external circulation pump as I believe these are put in purely out of laziness/lack of expertise of the designers, whereas in fact they are making the install and run far more complicated and expensive with these items installed. Get the customers to pay for these extras and pay again in wasted energy using them, so no reason for designers to worry about doing it properly.
There are some key mentions in the Daikin manual which are flags, and just as key there is zero mention of adding an external (CH Circ) pump to the CH system.
the only mention of a field supply pump is here:
My install has a 50 litre buffer, a Grundfos circulation pump and a Backup Heater. So, according to the specs, with a backup heater the minimum volume of water is just 20 litres, that's about 3 radiators panels/ large towel rails. I have the equivalent of 11 doubles, which is 144 litres plus the pipework. So in no circumstance would the install need a buffer tank. That 50 litre buffer represents about 33% of the total volume of the install, so that's 33% lost efficiency, 33% more expense in bills.
Now I have never seen a design for the system, it will be interesting what the handover pack will include.
I have also done some experiments on the CH Circ pump speed.
Turning it off or up to full speed doesn't affect the flow rate displayed on the unit, which must mean the internal pump is pushing water faster than the external Grundfos.
Turning the Grundfos off negatively impacts the CH flow, all the Rads went cold even though the F&R temps on the Daikin were at 37/35. Which means the buffer was acting as a bypass to the heating system without that extra Grundfos inertia
Turning the Grundfos to the slowest speed restored warmth to the Rads and the flow in and out of the buffer was <0.2C (delta).
At the moment my only interest is getting it through RHI. I'm not going to start messing with the layout as I need that MCS certificate but its something I will deal with later. A simple bypass of the buffer or ripping it out completely are my thoughts.
Giving this further thought, the buffer tank should only ever be in circuit as part of an automatic bypass system in case of end user error closing all the Rad valves.
......and in my case limited to a 20l buffer tank
some good analysis there. Have you thought of a change in career?
Seriously though, it isn't right that customers/users end up having to know more about their heating systems that the so-called experts. Imagine if you had to tell your electrician how to rewire your house.
Kev
- 26 Forums
- 2,123 Topics
- 46.7 K Posts
- 78 Online
- 4,531 Members
Join Us!
Podcast Picks
Latest Posts
-
RE: Planning Permission May 2025
In England that is no longer the case although you have...
By JamesPa , 11 hours ago
-
RE: ASHP heat output monitoring
As you know, you need the flow rate to do that, and I t...
By cathodeRay , 14 hours ago
-
RE: Ecodan - Legionella Operation Time and Target Temperature
Once the white plastic cap is removed, my immersion loo...
By Old_Scientist , 20 hours ago
-
RE: Replacing Refrigerant on Mitsubishi Heat Pump
@dgclimatecontrol I don't know, but they were not happy...
By DavidAlgarve , 21 hours ago
-
RE: Octopus Cosy & Octopus EV + bidirectional smart tariff, together. What, eh?
The current FAQ says it's not compatible with existing ...
By Old_Scientist , 21 hours ago
-
RE: Why do we need pressurised systems?
A good question @toodles. My old open thermal store and...
By AllyFish , 23 hours ago
-
RE: 300 Liter Tank - Do I have to heat it all?
Cross references for @martingale Background discussi...
By Transparent , 2 days ago
-
@ecobaker May I ask a question of you please. I too hav...
By Papahuhu , 2 days ago
-
RE: Share Your Experiences with Heat Pump Manufacturer Support
@terry1812 Oh Good! Pleased to help if I can! Regards, ...
By Toodles , 2 days ago
-
It's unclear to me how the Smart Control project work b...
By Transparent , 2 days ago
-
RE: Have Consumers Been Lied to About the Efficiency of Heat Pumps Made in China?
@pavel, this isn't about discrediting Chinese products....
By Mars , 2 days ago
-
RE: Solar Power Output – Let’s Compare Generation Figures
We had an excellent four months (11/3 to 15/7) generati...
By JulianC , 4 days ago
-
RE: Is this just haze or something more?
I think the present somewhat cooler hazy days show the ...
By Judith , 5 days ago
-
RE: My misgivings about installing ASHP and solar panels via the ECO4 scheme...
All noted and accepted and as I say I am sorry that you...
By JamesPa , 5 days ago
-
I think it is very much me that is sitting outside the ...
By Grantmethestrength , 5 days ago
-
RE: Who's your electricity provider and what's your tariff?
Aggregators have been recognised for many years, and it...
By Transparent , 6 days ago
-
RE: Help me keep the faith with my air source heat pump installation
Great news I edited my previous post (probably af...
By JamesPa , 6 days ago
-
RE: Double or Triple Glazed Windows?
@toodles Glad to hear things are progressing well for y...
By TRBob , 6 days ago