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Air Source Heat Pumps (ASHPs)

Last Post by Grantmethestrength 3 hours ago

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Grantmethestrength

(@grantmethestrength)

Reputable Member Member

Joined: 9 months ago

Posts: 122

Topic starter 19/10/2025 9:36 pm

Well the hits keep coming! I had a sudden loss of flow from 28 l/min to barely nothing so had the installers back in. I genuinely don’t believe that they flushed the system when it was installed in Jan. They were supposed to put in all new pipework but as per ECO4 regulations they cut as many corners as they could and tied into old pipework (obvs!). I stuck some cleaner in the system and then did a poor mans mains flush then fully drained down the system while they were on their way. The mount of crap coming out of the system was ridiculous the mag filter had tons pf crap in it but the saving grace and the root cause was the filter just before the ashp between the external volumiser and the unit. It was totally blocked.

The installer trashed it getting it out as it was completely stuck in there, now bear in mind this was serviced by Grant in June. I have ordered a new filter and the system is running smoothly again but I am really getting hacked off with the repercussions of a crappy install!

Now I really want to have a full system flush and I think that the honeywell 3 port diverter needs changing or at least removed and properly cleaned. I have been recommended the model below. Has anyone had any experience of them versus the honeywell as I am on my second honeywell already and the system isn’t even a year old

att.2GirJyWHGY79zfZW90KUJQcAKmxaOaO69VMDB0AUOO8

This topic was modified 4 hours ago by Grantmethestrength

Kind Regards
Si
——————————————————————————
Grant Aerona3 13kW
13 x 435w + 13x 480w Solar Panels
Sigenergy 10kW Inverter
16kW Sigenstor battery

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Mars

(@editor)

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Joined: 5 years ago

Posts: 3609

19/10/2025 10:01 pm

We’ve just had our system flushed and filled, and I can tell you, it’s not an easy or quick job to get right, so I can see why installers cut corners. There are various power-flushing methods and bits of kit you can buy, but in our case, the goal wasn’t so much cleaning the system as it was getting rid of trapped air.

The fill and flush valve we had installed worked brilliantly. It does need to be plumbed in… it then has one end that connects to a pipe leading outside, the other to a mains water supply. If you’ve got good mains pressure, you’re in luck. We only have about 1.5 bar here, but it was still good enough, and honestly, it was shocking how much muck we pumped out.

If you go down this route, I’d recommend fitting the valve and purging your system for an hour or two. Then add some system cleaner, let it circulate for a few days, and repeat the flush. You’ll be amazed at what comes out.

The fill and flush valve setup can be seen at the 3:42 mark in this video:

👉

There are loads of other ways to approach this, but once the valve is fitted that we used, this is something most DIY-minded homeowners could easily manage themselves.

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JamesPa

(@jamespa)

Illustrious Member Moderator

Joined: 3 years ago

Posts: 3129

19/10/2025 10:03 pm

Posted by: @grantmethestrength

↑

Well the hits keep coming! I had a sudden loss of flow from 28 l/min to barely nothing so had the installers back in. I genuinely don’t believe that they flushed the system when it was installed in Jan.

FWIW my flow crashed when I started my system up in July to attempt cooling for the first time, the space heating part of it having sat around doing nothing for a couple of months. I didn't realise however that this had happened because I wasn't, at the time, monitoring flow. Also I had flushed the mag filter which had very little in it, so assumed that there was no possibility of blockage. This didn't fix the problem!

There were all sorts of seemingly disconnected error messages that had me worried. So installer turns up, spends 5mins looking at the control box, goes straight to the filter like the one illustrated above and flushes it out. Pitch black, service fully restored. He remarked that 90% of callouts are the mesh filter (which I didn't even know was present. I get the impression it might be a regular maintenance item, obviously its a much finer filter than is historically fitted to boilers which is of course a good thing!

I know he flushed my system (which does have old pipes and some old rads) well when he fitted the ASHP, so I guess this may be par for the course. It doesnt actually take much grot to block a small fine filter!

Sorry I cant comment on the diverter valve.

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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Grantmethestrength

(@grantmethestrength)

Reputable Member Member

Joined: 9 months ago

Posts: 122

Topic starter 19/10/2025 10:08 pm

@editor Yeah I watched the episode and am probably going to swap out my inatec flow regulator as it looks like crap an yes it is less than a year old allegedly!

I like the idea of being able to easily flush the system. The earliest I can get a plumber out to flush the system is end of Jan and it will be quite expensive I have decided to upskill myself to sort out my own system!

Kind Regards
Si
——————————————————————————
Grant Aerona3 13kW
13 x 435w + 13x 480w Solar Panels
Sigenergy 10kW Inverter
16kW Sigenstor battery

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