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Ideally, the PRV set pressure should be set to the (dynamic) mains pressure with a big HW demand, your pressure may only be 2bar or so, it might even only have a static pressure of 2bar (even if unlikely), even so, the air end pressure will rise while heating takes place as water is...

Did the check the PRV (pressure reducing valve) pressure and setting, this is usually set to 3.0bar, you can do a few tests yourself if so inclined and you have a tyre pressure gauge. Shut the mains isol valve before the multibloc and open a hot tap to depressurize the cylinder, attach the PG to...

What about your "Whistling TRV" post #3??, is it still whistling??

Is the ABV setting still set to 2?.

Suggest leaving that rad as is because you do need a minimum flow which may not happen if all rads are TRVd, unlikely that all will fully close at the same time but you never know?. I installed a normally open motorised valve in place of a ABV a fair few years ago for a friend, it closes as...

Yes, but when the CH zone valve closes does it also stop the circulation in that rad with no TRV?, if it does, then no good, because the main purpose of a ABV is that it allows circulation to cool down the Boiler HEX for a few minutes with circ pump overrun, does the circ pump run on for a few...

I think its almost universally accepted that 1 meter = 100 mbar so if one reads the scale as meters then good enough? since the pump head is normally in meters.

There is a problem with using a ABV (automatic bypass valve) with most modern A rated circ pumps in that the pump head doesn't fall off rapidly when the flow demand increases or more importantly doesn't increase rapidly when the flow demand (like zone valve or TRVs closing) decreases, you can...

Not familiar with the 145 but clockwise yes to increase the lifting head.

That's correct, yes, the index is in meters, M, I thought they were in (decimal) bar.

You should still be OK at that setting, if all rads not heating or very slow then press the button to get one green + one orange LED, that gives a 5.2M head and hopefully not too much noise, I would also increase the ABV index setting to ~ .35 to .38 (3.5M to 3.8M) after reducing to speed I, if...

Thats your problem almost without any doubt, the UPS3 is a giant of a pump and is dispatched set to full speed, III on CC3, it will be circulating at a massive head of 6.4M up to a flowrate of over 19LPM, 1.15ms/hr. Just press the setting button briefly a few times until you gret just one solid...

Your pump Head is possibly too high, can you post the make/model/mode & its setting or post a photo of it running with the LEDs clearly shown.

I have a simple FantiniCosmi digital roomstat in a combined (two rooms) dining and living room with two rads and where we spend 99% of the time, the heating is switched on at 0700hrs and switched off at 0100hrs each day, roomstat set to 19.5C during the day and 20.5C (sometimes 21C), from around...

Mechanical TRV "fully open" stroke varies with the setting, the lower the setting, the less the stroke/opening when "fully open", so obviously cannot maintain a set temperature (see below) depending on conditions, however, in tests I did years ago I found that the hysteresis, at least on the one...

Know several peoplw with these "recalled" pumps but not one of these has been replaced as of yesterday.

Why not stick a pressure gauge on the (unused) balanced cold out, if you (or your plumber) shuts the isol mains valve then the incorporated non return valve in that combination set will/should stop any water coming back from the cylinder, just slacken the blank after shutting the islol vale to...

What make/model Boiler do you have?

That pressure gauge (looks like it) measures the mains water pressure after the PRV (pressure reducing valve) and is the supply to the unvented HW cylinder, if so, has nothing to do with your problem. If there is a pressure gauge on the front of the boiler, check its reading, should be...

On one boiler, the latest version, the pump wasn't reducing speed low enough to get a fairly modest set dT of 15C, on the other boiler, (previous model), the pump speed was/is reducing far too low to 15%, to give a residual head of ~ 0.07M, 7mb, which is far too low to give a balanced flow to...