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Ecodan flow rate tweak

Air Source Heat Pumps (ASHPs)

Last Post by Gary 2 years ago

6 Posts

3 Users

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Jingle86

(@jingle86)

New Member Member

Joined: 2 years ago

Posts: 3

Topic starter 25/01/2025 3:00 pm [#2054]

Dear all,

I currently have the setup below.

- Zubadan PUHZ-SHW140 YHA (-BS) outdoor

- Ecodan ERST20C-VM2DR1.UK indoor

My dT is 10 around freezing temperatures, and I want to lower that by increasing the flow rate.

I adjusted the pump speed to 5 (maximum), but it doesn't give me a lot of flow. My outdoor unit supports a flow between 18 and 37 liters per minute, according to the specs. The max flow of my indoor unit is 27 liter per minute, but I only reach 21 liters per minute (probably piping, height resistance, etc). There is no button to control pump speed on the pump itself. The water pump is a Grundfos UMP3K 15-75-130.

I see that there are other indoor units (E*PT 20X series for example) that have the exact same water pump, but according to the specs of those units they have a max flow of 35 liters per minute. Besides, when I look up the specs of the water pump on the website of Grundfos, the max flow of my pump is much higher than the 27 liters (or even the 35) per minute.

I think the pump speed is restricted by the indoor unit, even when it is on speed 5. Unplugging the CNPWM doesn’t set the water pump on max performance either.

Does anyone have ideas how to increase the flow by speeding up the pump (which should be possible according to the specs of the water pump)?

Quote

JohnR

(@johnr)

Estimable Member Member

Joined: 2 years ago

Posts: 106

26/01/2025 9:50 pm

1. Are all your radiator valves (both any thermostatic valves and the lockshield valves) fully open?

2. What diameter is your pipework to the radiators?

3. What size house?

ReplyQuote

Jingle86

(@jingle86)

New Member Member

Joined: 2 years ago

Posts: 3

Topic starter 26/01/2025 10:54 pm

@johnr

Thanks for your reply.
Yes all radiators and floor heating is fully open. Pipes are 28mm or bigger. It is a 15kW heatpump used for both a big farmhouse and an apartment.

I think the 21 liter (out of the max 27) corresponds with the height resistance etc. I don’t think I can improve much on the piping and radiator sitution itself.
Therefore I am looking for alternative solutions to increase the flow.

ReplyQuote

Gary

(@gary)

Reputable Member Member

Joined: 4 years ago

Posts: 350

27/01/2025 10:01 am

I would give the Mitsubishi customer help line a call, the manual does say if you want to get max flow you will need to install an additional pump, see below.

Mitsubishi do recommend dT8 so you aren't miles away from that, you don't say why you want to decrease it from 10?