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Thanks John, I will do that. That is where I picked up that replacing the HEx would likely solve my low actual flow temperature issue, as it did. But like in that case, since the replacement I now have actual flow temperature several degrees ABOVE the set and indicated flow temp! Not very...

Thank you John. Yes, I'm not chasing 20C really and am being satisfied with 12-15C drop at the rads. Yes, we do have TRVs on 8 of our 14 emitters (not on towel rails or on rads where the room stats are) but I balance with them all at maximum and coolish rooms. Have continued with balancing...

That's a good question, John, that I have sort of been asking myself - but in a somewhat different way. I dropped the pressure from the default 250mb in order to try to reduce noise from the lockshield on the rad nearest the boiler (it's actually very near). With the system balanced, all the...

OK John. I'm taking the opportunity of the colder weather today to check the balancing of my whole system this evening but I will try to do some readings as above asap.

But am I right in thinking that would not comply with the Building Regs? And I'm no expert, but I don't really understand how that helps with only needing a bypass during pump overrun and not at other times. If one were to go down that route, would it not be more logical to have something like...

Thank you John. That is helpful. I may have a couple of Honeywell ABVs for sale 'ere long!

I've been having exactly the same thought, John, that an MV interlocked as you suggest would be a more positive and less tricky solution than an ABV that neither shuts off properly or will definitely open when required! Is the interlock signal/power needed generally easy to obtain from the...

Thank you John. The pump map is definitely set to ‘Delta-P dependant 1’, ie 150mb. The other info displayed re the pump is: Control mode: ‘Heat demand’ (the alternative is ‘Energy saving’); Block time: ‘0 sec’; Overrun: ‘2 min’. In ‘Hydraulics’ the info is: ‘Low loss header: Off’; ‘DHW...

Thank you again John. Responding to your points made and asked in your two posts above in order: Pump pressure against closed valves: Given the pump modulation of 20% I am observing during pump overrun, what is the point of the ABV and the overrun if the pressure generated is nowhere near the...

Seems like everyone is too polite to comment on my resistance musings above! Meanwhile, I have now retested my removed and serviced ABV (Honeywell DU144) using a simple gravity feed arrangement with a head of 1.43m, which equates to 140mb pressure. With the valve set to 400mb, the leakage rate...

I've been pondering a bit further and think I've come up with a simpler and probably better method for testing the removed bypass valve. But more of that later, as I've also been trying to get my head around what the boiler and pump will do in response to a high external system resistance, both...

I completely agree, John, but this is what I am faced with - both the new valve and the old one. Building regs require an automatic bypass and not a fixed one. Surely one that works is not asking too much of modern science?!

Thanks again John. I have a BS4613 dial-type tyre pressure gauge, which is marked in 0.1 bar steps, so I used this (at the top of my rig to avoid getting water into it!). The water supply was from the mains via a good length of hosepipe and I had the valve discharging into a large bucket. A...

Hmmm …….. I just don’t know what to do or say further. It would be really helpful if there were a full diagram somewhere but that doesn’t seem to exist. Hopefully someone may be able to throw some light because I feel stumped.

OK, I've now tested the serviced valve to see how well it shuts off; as I rather expected, it doesn't. At all settings it lets water through, more so at low settings and low applied pressure. Given that the valve consists of a hard plastic jumper attempting to seal onto brass, it's not...

Thank you Mister Banks. However, it's not other things I am concerned about here; it's what the ABV is doing. Please see my post just added a few minutes ago.

So, I have cleaned all the internals of the old DU144 bypass valve and all now moves beautifully freely. Not that easy to remove what were magnetite deposits but quickly oxidised to rust - but it is done. Very easy to see how contamination can cause the valve to become stuck open. However, is...

Meanwhile, I have been thinking that I don't actually know how much flow is occurring through the ABV. All I know is that flow temperature water is going around the loop (more exactly now measured at 8.5m of 22mm pipe) and back with very little drop in temperature. However, the whole of the...

Thank you John. Yes, I will try to set up the cleaned old valve in my rig and test at what pressure it opens. Watch this space! May take me a few days to scrounge the time ………. But I will be back.

Hi John. Here are the requested readings: Pump map 1 (150mb) Pump modulation 50% Set flow temp. 60C Indicated flow temp. 63C Actual flow temp. 64.3C Burner modulation 19% (6kW) Actual return temp. 54.7C Pump map 2 (200mb) Pump modulation 56% Set flow temp. 60C Indicated flow temp. 61.5C...