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Took the 4 allen screws off the pump and pulled it apart but its sealed behind so didn't get to look at the impeller, wasn't sure if it was a good idea to prise it apart so put it back together. With the discharge gate valve closed I get:- CP1 = 11 (about 2 lower than graph) CP2 = 26 (about 4...

Nothing to lose I guess, another fun evening in the airing cupboard :cry:

Except I have these Drayton auto balancing valves fitted which definitely restrict the flow on the CH side. But this doesn't explain the quite low wattage readings I am getting from the pump when HW or ABV open, it seems I'm not getting good flow.

I had the 22mm section part where the HW valve is to T in the ABV, no scale and didn't look too bad, the F&E is fed from a softened feed so hopefully that reduces scale. The cylinder is date stamped Jan 2021 so quite new, don't think the coil has any restriction. The only other possible...

The valve is fine, I had to take if off when I was fitting the ABV, the valve rotates fine, motor is fine, didn't look too dirty either.

I also checked fixed speed II on HW only and this reads 15W, doesn't this mean the flow is still very low looking at the graphs?

Readings on HW only CP1 15/16W CP2 26W III 39/40W

Yes its on the 22mm out of the bottom of the tank coil, its set wide open although I think I read cyclinder balancing is now banned by building regs as the programmer should have separate timers for HW/CH that can be offset in time so no balance required. I think it ramps up and down then...

System I've inherited when I bought the house a few months ago, some rads were probably circa 40 years old. To summarise: British Gas 330 boiler, circa 2006, serviced and seems fine. Pump Grundfos Alpha 2 15-60 130, date code of PC 1806 which I assume is June 2018 All rads replaced with brand...

Yes, with CH on the boiler short cycles so the rads are taking ages to get any heat, the boiler runs for a minute or so then cycles off for about 5 minutes.

The boiler can modulate down to 6.3kW according to the manual. The boiler only shows water temp, I see it rise rapidly to around 50-60C then it seems to decide that rate of increase was too high so cycles off for a few minutes. With the ABV open the boiler doesn't cycle like this, the temp...

CP1 difficult to tell if there is a change with ABV open shows 16W when closed either 15W or 16W though. On fixed speed 3, 40W ABV closed, 42W ABV Open Some of the ripped out lower radiators had a small amount sludge, one of the old 30+ year old TRVs was a bit sludged up, magnetite filter was...

Yes, vented system, tank in loft all ok, drained it recently while fitting all the new rads / valves / ABV etc. Cold feed all ok only refilled system on Monday. Don't think the system has any bleed or bottle air vent that I can find. S Plan system with CH and HW motorised valves. Will report...

That's my feeling but maybe I've missed something stupid? All rads on, 13 plus 2 towel rails. PP2 showing 9W, speed 3, 38W, did show 42W earlier, ABV is max setting so its closed. From the date code 1806 I assume June 2018? nearly 5 years old? My only other thought is whether I have air...

Yes, nothing on the valve body, pins out, only restriction is the valve itself. All lockshields are wide open as recommended.

Last readings I took were with all TRV heads removed, valve balance index set for dT15 degrees, CP1 fluctuacted between 15/16W, CP2 between 26/27W. On CP1 the boiler was short cycling, close to kettling I would say, CP2 seemed to just about hang on. The boiler has a max rating of 31kW but as...

They use the same TRV4 head on the valve or a Wiser smart head to shut it down for temperature control. I'm still struggling with the whole system though. With the all the TRV heads removed and the balance values set for dT20 all the valves added together should allow a flow through the system...

Me too, thanks again for your help!

Thanks, I'll try CP1 Another question, what is the formula to calculate the approx LPM per kW for a given dT?

I see, that's what has confused me. So it seems things are normal then but still leaves the question of which pump mode to use from PP1, PP2, CP1 or CP2, how should I determine which to use?