Super_Paulie

I've had to pop out this evening but I like what you've got there, I'll set up a schedule on my stat and try that out. I've also increased my mixer to 50 as I've still got room to play with on floor temp and I've got a boiler flow temp of 57. This is all higher than I had hoped but needs must if that's what I've got to do.

Thanks for that that. That is how i would like to go really due to my boiler modulation being shitty, heat that thing up, let it radiate for long periods, thats what i did all winter really. Do you have any suggestions for me John based on the above? I havent had any heating requirement for 17hrs now but its within a degree of the stat calling as we speak. My flow of 57, mixer of 45, bypass rad open 1/4 keeps my return within the range for condensing but with a decaying cycle time ultimately ending the evening on a 8minute cycle.

i understand this. No matter what i set that flow to the floor will eventually fill up, quicker or slower based on flow temp, and at that point im back to square one. Just like when i tried it low and low and then hot and fast, my usage was nigh-on identical. So no matter what i do to this my efficiency is going to be the same, its about finding the point where im condensing for longer i suppose to try and win back a few pennies and not ruin the boiler through super-low cycles?

I can do that tonight when i get back in, no problem. When i first started testing last night, the system had been on for a few hours that the cycle time had a decay after every cycle, down from 15 minutes when i started to around 8 by time the system went off. Should i be taking my readings once the system is up to temperature but still calling, say after an hour of running? Also the flow and return temps, should i take them at the boiler, so the flow reading on the screen and the return reading from my probe (after the buffer)? I was under the impression after the boiler has stopped firing the screen will then be showing the return temp rather than the flow as there is no flow. Could be wrong on that. I have made a daft spreadsheet table to record what i think might help out. Thanks loads you guys. boilerTemps.xlsx

Ok I've made that adjustment. I'm up to temperature now so I can't really get any numbers but hopefully I'm heading in the right direction. I did see that my cycle times were getting smaller with every cycle, my last cycle time I recorded this evening was quite short, 57 boiler, 45 mixer, 8 minute cycle.

Ha ha, my understanding gets worse 😆. I thought that by opening it up it would emit more heat and thus bring down the return temp. Think I'm beyond saving at this point. I'll knock that lock down now 👍

I can do that. Sorry John, my understanding of flow rates seemingly can't be solved. I'll open up that shield a touch and see what that brings my return down to.

Very interesting, thanks. I've looked to see if I can edit the anti-cycle time on my Baxi, but alas that seems not an option. How could I reduce the bypass flow rate, just via the boiler flow? I am trying out 57° this evening which is giving me that lower return. Like I say, that thing is tiny but so is the room. It's toasty in there though now my flow temperature is up at 57°, actually warms the top floor if I leave the door open.

John, thanks a lot. Ive been trying to get my head around this on my lunch at work but i just cant comprehend it, im just not educated in boiler flows im afraid. Im not sure what numbers to change to "make this better" so my apologies. Your effort is way beyond the call of duty, but im a mere mortal 😆 So it looks like a "low and slow" way of doing business isnt going to work for me due to not having a boiler than can modulate down far enough, but rather a "batch heating" of the floor just when i need it and accept a 15 minute(ish) cycle time, thats no problem as thats what i was doing until a few weeks back. Having this at a 60 degree flow, 45 mixer is ultimately higher than i wanted on both sides but that gives me a cycle time of around 12, lets say 15 minutes. I have it with a very small bypass rad currently and my house IS warm enough but ultimately i am heating a water tank in the loft that is just sitting laughing at me asking for more money. If there is any way i can get this flow rate down without the system cycle or am i just at the limit due to the boiler? I will be getting a bigger rad and snaking the return under the bathroom floor as a makeshift UFH, that wont add a huge amount of volume but it would take more heat away. Ok, so this costs a few quid a day to keep my family warm, im not going to lose any sleep over that. Thanks so much guys, what a great forum this is and has been in my build so far.

Yeah it's dead on 7 lower, the actuators see to that and seemingly work a treat.

That's interesting, thanks for that. So volume is the thing, I could probably increase that with an additional rad say in the hall plumbed in before the 2 ports. But what advantage would I gain from this increased volume, longer cycle time?

Ah, gotcha. Ok so maybe my probe is a better indication rather than what is on screen. I'll have to do that tomorrow as the missus is back in, boiler in loft, manifold ground floor. I've sat looking at the manifold the last 10 minutes and to be honest the needles barely move at all, maybe a degree or do. All flow rates are 2.5, ish, balanced with Salus. Yeah the smart meter was £2.50 so it's not going to be much higher by the time it goes to it's set back at 11, and 30p of that is the standing charge. It'll stay 20+ in here all evening no doubt.

It's always around -10° no matter what I set the flow at it seems. 65 drops to 55. 55 drops to 45 etc. It just drops to whatever temp is in the tank in those 3 minutes. I have absolutely no "off time" except when it's in that anti-cycle mode.

I've likely misunderstood what I've been trying to achieve here. In fact, I'm not even sure what that is at this stage. I guess my tank just creates volume and not a lot else. So tonight I ran a few tests. I locked off both upstairs rads which get a slight reverse circulation I think as they warm slightly when the UF is running. Ive been using a probe on the return under the boiler to read that but instead I'm going off what it shows on screen when it's not firing and that is surely the return temp. I went with: Boiler 60, mixer 45. Bypass rad (tiny thing, shown above) 3/4 open. So it now fires for 9 minutes as it creeps 60+5. Flames out with a 3 minute anti cycle and the return temp drops to 52 at the tank but shows 56 on screen. It then fires back up and repeat, which I guess is a cycle time of 12 minutes. So guys, ultimately what is my goal here, I'm not entirely sure anymore. Keep the boiler firing for as long as possible until it reaches overtemp and flames out? For what it's worth, it's toasty warm in here at 22/23° and it's cost me £2.50.

really appreciate all this help guys, its helping me understand this all a bit better. The numbers give me brain struggles so its very much appreciated. I have re-drawn my system to maybe show a bit more of the reality. Looking at it as you say, 60 (65) down to 50 once the UFH is away is a big old drop for what should just be a bypass. I do get some, what i thought was, reverse circulation in the rads marked Rad1 and Rad2 in the attached image. Would that combined with the bypass rad in the bathroom account for the loss? To test this should i lock off the 2 rads and see if the return temperature increases? As it is my boiler burner is essentially "never off", and is only off when it flames out at the temp +5 for the anticycling time of 3minutes. I kinda expected the return to get so high that the boiler stops the flame but then continues to pump while being fed from the buffer for however long it takes, not just being off for a pre-determined flame off due to anti-cycle. Probably totally miss-read the situation there.