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Low Flow Rate Error - 8 kW Ideal Logic ASHP - Help!

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Air Source Heat Pumps (ASHPs)

Last Post by cathodeRay 4 weeks ago

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Wh0am3ye

(@wh0am3ye)

Eminent Member Member

Joined: 7 months ago

Posts: 10

Topic starter 10/10/2025 4:33 pm

Hi all,

Heating has been kicking in more frequently this week and I am now getting a reccuring low flow rate error on my system, 370F27. I can clear it for a few minutes by switching it off and on again but it appears to be persistant and coming back each time.
I called up the Ideal Customer Support and they said it may be due to air in the system or a blockage and to contact my installer. We had an ECO4 install, and my installer has been diabolically slow to respond to any issues since they completed the install, so whilst I will get a response there is no guarantee when (current record is 6 weeks between us sending a message and recieving a response from them! And then they'll need to actually get someone out to us which is a whole other nightmare.)

I have cleaned the magnetic filter and checked all the automatic bleed valves, I also bled the radiators and topped up the pressure to just above 1.5bar. All to keep my Primary flow rate sitting at 13l/min which is 1.5l/min below the minimum flow rate for the system. 😩

Does anyone have any idea of what I might be able to do to increase the primary flow rate so I can have some heating as if it continues to not work, by the time I get a response, my 170 year old stone cottage will have settled back to it's happy place at around 8-10 degrees or just below whatever the outside temperature happens to be! 😱

TIA!

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cathodeRay

(@cathoderay)

Illustrious Member Moderator

Joined: 4 years ago

Posts: 2354

10/10/2025 6:07 pm

@wh0am3ye - do you have so called primary and secondary circuits (ie some form of separation of what goes through the heat pump and what goes through the rads)? If so, I guess the magnetic filter is on the rad circuit, but there is usually also one on the primary circuit. If there is, have you checked that? Mine is in something that looks like a ball valve, but the ball is actually a filter that unscrews from the bottom closing the valve (and reopening after checking/cleaning!).

Midea 14kW (for now...) ASHP heating both building and DHW

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Wh0am3ye

(@wh0am3ye)

Eminent Member Member

Joined: 7 months ago

Posts: 10

Topic starter 10/10/2025 6:13 pm

@cathoderay As far as I can tell, there is just the one filter, on the heat pump side of the cylinder (bottom left in the photo), I attempted to clean it out earlier on, but wasn't able to remove the mesh inside. Perhaps I need to have another go at that as watching the only video I can find online with my issue, the flow rate was being limited by a blocked filter.

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cathodeRay

(@cathoderay)

Illustrious Member Moderator

Joined: 4 years ago

Posts: 2354

10/10/2025 6:24 pm

@wh0am3ye - can't make out all the details from that photo - is it separated (primary and secondary circuit) or just one big open circuit?

Either way, you need to get the mesh filter out of the magnetic filter, blocked mesh filter and low flow rates have a natural affinity!

Midea 14kW (for now...) ASHP heating both building and DHW

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Wh0am3ye

(@wh0am3ye)

Eminent Member Member

Joined: 7 months ago

Posts: 10

Topic starter 10/10/2025 6:49 pm

@cathoderay Honestly, I'm not sure. The flow and return come from the heat pump, in to the cylinder on the left side and then the flow and return out to the radiators comes out the cylinder on the right side, where the pump is. I don't know if there is a secondary circuit or not.

Sounds like the plan for this evening is walk the dog, have dinner and dismantle the filter again! I'll update when I've cleaned it and see what happens!

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cathodeRay

(@cathoderay)

Illustrious Member Moderator

Joined: 4 years ago

Posts: 2354

10/10/2025 7:14 pm

@wh0am3ye - it's just possible that is a huge buffer, the mother of all buffers, not sure. What about DHW, is that entirely separate, with a diverter valve? We can explore more tomorrow.

Meanwhile getting that filter out makes sense. Mine does sometimes need a firm pull to get the mesh but out, it gets a bit stuck at the bottom. If you can find a parts diagram (or cross sectional drawing) for yours, you can reassure yourself that you cam make sure you pull in a way that won't do any damage.

Midea 14kW (for now...) ASHP heating both building and DHW

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ASHP-BOBBA

(@ashp-bobba)

Honorable Member Member

Joined: 11 months ago

Posts: 291

10/10/2025 7:56 pm

@wh0am3ye Check out by the ASHP on the pipes next to the unit and see if there is a Y strainer this is usually the culprit to look for 1st

AAC Group Ltd covering the Kent Area for design, supply and installation of ASHP systems, service and maintenance, diagnostics and repairs.
Professional installer. Book a one-to-one consultation for pre- and post-installation advice, troubleshooting and system optimisation.

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Mars

(@editor)

Illustrious Member Admin

Joined: 5 years ago

Posts: 3678

10/10/2025 8:33 pm

@wh0am3ye, as @ashp-bobba has pointed out, most flow errors on heat pump systems are caused by a blocked Y-strainer. What's remarkable about them is that they don't require a lot of dirt/corrosive bits to cause the issue. This a good starting point.

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ASHP-BOBBA

(@ashp-bobba)

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Joined: 11 months ago

Posts: 291

10/10/2025 8:44 pm

@editor we now fit 800 micron Y strainers rather than the very standard 100Mic, Samsung and a couple of other makes are very sensitive to low flow and we found when servicing as we don't fit Samsung units that the 100Mic can sometimes halve the flow in a clean system, the 800 reduces it by about 10%.

We also sometimes go as far as fitting 35mm Y strainers on a 28mm pipe with reducers just to give a system less restriction but the same protection, just another example of a littler further for it to be a little better, also we actually go back to our installs and service them year after year so helps us not have annoying low flow issues.

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Wh0am3ye

(@wh0am3ye)

Eminent Member Member

Joined: 7 months ago

Posts: 10

Topic starter 10/10/2025 8:48 pm

Thank you for all your responses!
I gave the magnetic filter another clean and got the mesh out this time. Flow rate back up to 24.5l/min! Success!
I will take a look to see if we have any Y-strainers tomorrow and give them a clean as well if so.

👍

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ASHP-BOBBA

(@ashp-bobba)

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Joined: 11 months ago

Posts: 291

10/10/2025 8:51 pm

@wh0am3ye super, glad your back up and running.

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cathodeRay

(@cathoderay)

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Joined: 4 years ago

Posts: 2354

11/10/2025 7:00 am

@wh0am3ye - good news about the flow rate being better after cleaning the mesh filter.

Posted by: @wh0am3ye

↑

I will take a look to see if we have any Y-strainers tomorrow and give them a clean as well if so.

Bear in mind the filter if fitted may look like a large ball valve with a cap screwed into the base (as mine does) rather than a Y strainer.

I also think it is still worthwhile identifying the basic design/layout of your system, if only for future reference. I am now more inclined to think that what I thought might be the mother of all buffer tanks may in fact a DHW cylinder, but it is by no means clear. For example, the pump visible in the photo appears to gave been labelled CH1 - which suggests central heating, not DHW.

Midea 14kW (for now...) ASHP heating both building and DHW

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