burgessl

I remember the old Potterton boiler we had (basically a Baxi) behaved like this - once up to temp the burner would shut off for a few minutes with the pump still running, then ignite again and repeat. Checking it looks like the 3 minute anti-cycle time does seem to be fixed on the Baxi boilers - a snippet I found in the manual:

@John Carroll I had a chance to run a couple more tests and finally found a few minutes to write the results down for you: Constant dP, target pressure 100mbar - this was after a while of running so hopefully steady state rather than ramping up: Modulation: 34% Target Flow: 62 Actual Flow: 62 Actual Return: 46 Flow rate: 477 l/hour Pump speed: 21% Fixed pump stage 50% Modulation: 32% Target Flow: 62 Actual Flow: 62 Actual Return: 48 Flow rate: 505 l/hour Pump speed: 50% I have to admit I haven't had a time to fully digest your posts yet sorry

The 1st set of readings are the baseline for my current configuration - spread hydraulic mode with a target spread of 10 with weather comp on so low flow temps and actual measured delta t of 5C The second two readings where at a target spread of 20K with a flow temp of 62 which I think was what you were after.

Ah thanks, I don't have the gateway and app (yet) so no wonder I couldn't find it!

@John Carroll I can some tests on my Ecotec plus 625. I do not have a LLH installed. I do have TRVs on all but four radiators (14 rads total) but they are fully open. Normally I run this with weather compensation with a curve of about 0.65 and I had set the hydraulic operating mode to spread with a target delta of 10K. Generally the spread is ~5 between flow and return which is not surprising since the flow temperatures at that curve are usually in the high 30s. When set to the default of dP constant at a target of 200 I'd see flow rates vary from ~700 l/hr to 1200 l/hr with often a delta T of only 2-3. The 'before' stats running as above: Modulation: 12% Target flow: 37 Actual Flow: 37 Act return: 32 Flow rate: 754 l/hour Pump speed: forgot to take this - I suspect ~30% With the boiler set to a min flow of 62C: First reading after about 5 minutes of running: Modulation: 54% Target Flow: 62 Actual Flow: 62 Actual Return: 43 Flow rate: 818 l/hour Pump speed: 34% Second reading about 5 mins later: Modulation: 39% Target Flow: 62 Actual Flow: 62 Actual Return: 49 Flow rate: 836 l/hour Pump speed: 35%

It's real - my boiler chugs along at just under 4kW. Shame I didn't argue harder for a smaller boiler (eg the 620 or lower) which go down to 2.7kW minimum.

@j_s where do you find the efficiency values? I've got an ecotec plus 625 installed October '24 but I can't see anything reporting efficiency in the boiler data or on the sensocomfort controls.