Does that mean the pump will run 24/7 ?The calc for KW is, KW= m3/hr*16.66*60*deltaT/860. = 0.85*16.66*60*12/860, 11.86KW.
This the ref I have to D.18. (1 is the default)
View attachment 47439
Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
Welcome to the forum. Although you can post in any forum, the USA forum is here in case of local regs or laws
Does that mean the pump will run 24/7 ?The calc for KW is, KW= m3/hr*16.66*60*deltaT/860. = 0.85*16.66*60*12/860, 11.86KW.
This the ref I have to D.18. (1 is the default)
View attachment 47439
HiOne would think that it should control as you say, above.
Another often discussed item is the power output and duration during ignition sequence, some say its 80% for 60 secs, others say 80% for 20 secs. You can get a good feel for this by noting the (pump) flowrate, the deltaT and the fan speed, d.34, during normal operation, then sometime when you next start up the boiler just watch and note the fan speed d.34 at start up and the time it remains at this speed before changing, can then calculate the output as fan speed is almost directly proportional to power output.
No real thoughts on room stat, its switching in at SP-1C (should be SP-0.5C) and off at SP-0.3 but should be SP so 0.3C error at this end, maybe faulty controller but not a huge problem?.Hi
did a single observation ( Wife was pressuring me to do lunch 😂 )
Fan speed initially 400, quickly dropped and stabilised at 277, stayed there for 1 minute exactly, then dropped to 150 for around 20 seconds then climbed back to 277 for 30 seconds then cut out.***.not sure what that means, if anything 🤔
also have been running steadily @62oC (10oC DT) for past few days, very stable, although boiler does modulate up & down a lot....tried increasing to 64oC to help warm up the house quicker, but it then it increased firing, expected but continued to 67oC and cut out 🤯, seems unacceptable that a boiler can’t fire up just enough to give a 2oC raise in temperatur.e, of course a 5oC tolerance would, likely have made this possible.
UPDATE
on normal running@ DT 10oC 0.7m3/Hr target 64oC the fan speed modulates between 143 & 192, doesn’t sound a lot, but can be heard. With proper tuning, this differential should slowly decrease & the modulation should be minimal.
I wondered if the PP setting on the pump could be responsible for varying the pump flow, chasing the continual boiler modulation 🤔 so switched the pump to CP2, 0.6m3/Hr and lower Watts 👍 and immediately the modulation stopped 👍 the fan is now constant at 150, occasionally it goes up to 154, then falls back to 150.***..so much better than the constant noise of the boiler firing up and down, although being in the kitchen it cant really be heard in the lounge, although the modulation could be heard in the spare bedroom, which is immediately above the boiler, but not any longer 👍
wonder if this pump behaviour is normal, or just ‘ one of those things’ 🤔
Any thoughts on the room stat question ???
thanks
re room stat, is the 0.5oC offset setting, ‘ shared’ either side of the target temperature?No real thoughts on room stat, its switching in at SP-1C (should be SP-0.5C) and off at SP-0.3 but should be SP so 0.3C error at this end, maybe faulty controller but not a huge problem?.
PP mode would certainly seem to be a bit erratic, I wouldn't have thought it should behave like this.
Now that its settled down at 0.6 ms/hr and 1500 rpm, what are the flow/return temps??, I can then give some numbers.
HiThat changes things so, it might mean that the boiler is outputting 12.9 kw for 60 secs which is closer to what some users are finding, if correct it means that the deltaT for that 60 secs or so is 18.5C at a flow rate of 0.6m3/hr and means that the flow temp at start up or re firing is < 45.5C to avoid exceeding a target temp of 64C. I feel that a flow rate of 0.8/0.9 m3/hr is the optimum, unfortunately PP3 which gives that causes modulating, if the pump watts are not changing then it points to a very/over sensitive boiler controller bearing in mind that a change of 1 watt in PP3 mode only results in a flow change of 0.08 m3/hr.
Might also be worth talking to DAB re a replacement pump as it was stopping on full speed originally which it certainly shouldn't have been so faulty?.
Your old pump I think gives almost your exact requirement (will look at pump curves again), so maybe take the top off it and see if its sludged up.
Thanks, completely forgot about that, your memory is better than mine 😂 have emailed DAB & will check other settings again......The pump was running at its maximum setting of constant curve 3 which shouldn't have caused the below.
See post 126 on page 11, also post 123 on page 11.
I would watch the watts on PP3 again and if no deviation then difficult not to conclude that you have a hyper sensitive (or faulty) boiler PID controller.
But if the DAB is displaying LOW FLOW again on full speed 3, I wouldn't be too happy and would contact DAB.
"UPDATE
1- I have set the boiler to 18KW, first time ever....its modulating ok, but have had to reduce the target temperature to 68oC to keep the inlet below 55oC.***.so quite a low DT
2-occasionally the pump declares ‘LO FLOW’ then shortly after shuts off, restarts with the same message, then after a few minutes reverts to the previous readings I.e. 0.7m3/Hr etc....set it to heating only for now to establish that works ok."
Exactly my thoughts 😎CP3 30W 4.5m 0.9m3/Hr....will leave as is amd see how the boiler performsMaybe no harm to check that full speed setting again as there may have been some air in the pump after installation, if "no flow "not annunciating now then pump OK IMO.
I thought CP3 is fixed speed 3 🤔 there is CP PP and the other one which AFAIK is for underfloor heating, does that make sense ?CP3 wasn't the problem No Flow, it was fixed speed 3 @ 36W AFAIK, even if you never use this mode, the pump should run at this setting with no problems.
Nothing really adds up from the above numbers, wonder if the thermistors are faulty or improperly attached to the flow/return pipes.Trying CP3 28W 4.5m 0.8m3/Hr 62oC target DT 19oC Boiler started modulating fan speed 145<>177 consistent. Then later when I checked, it was 150 and steady, no modulation ??? Then within seconds of me looking at it, it cut out ??? Can’t see why though 🤔 took 3 restarts and stayed running, started modulating again 145<>180
it seems, sometimes at least, that the boiler decreases it’s firing with each successive restart, which allows it to eventually stay running, is that how it works, or am I imagining it ???
Could it be the f,ow isn’t 1.0m3/Hr ? As this is a calculated flow, not sure how accurate that is....A deltaT of 9c = 10.47kw, more like it but the fan speed is a mystery as IMO it should be ~ 3024, as I said above, progressively reducing the output will tell alot, ie if deltaT still remains the same at a d.00 of 6kw as at 12kw then the boiler isn't outputting 10.47kw.
DT 6oC fan steady 150 assume boiler limited to 5KW Target 62oC, actual 62-63oCWill do the calcs in a minute, is the flowrate still indicating 1.0M3/hr?, this is important.
Will take 24 hr gas readings over next 3 days, last week I used exactly 3 units in 24 hours, but will compare in a few days. Talking about plumes, so is it possible to see a plume if no condensing is taking place ?, hoped that was a sign that it was 🤔Even though I am reasonably happy that a fan speed of 1500 RPM is min output of ~ 5.2kw, this is not borne out by using the flowrate of 1M3/hr and a deltaT of 9C which gives a output of 10.46kw, if the deltaT is correct then the actual flowrate is only 0.5 m3/hr for a output of 5.2kw, if the flowrate is correct then the deltaT is only 4.5C. Would like to monitor the gas meter.
Condensing: Achieving the utopia of 100% condensing requires a flue gas temperature of down around 30C which requires a return water temp still lower of ~ 20/25C, so you will always see a plume from the boiler unless these conditions are met, IMO to achieve ~ 3/4% condensing benefit requires a return temp of ~ 45C, the big advantage of condensing vs non condensing is that even when not condensing there is a big benefit, a non condensing boiler might have a flue gas temp of 230C (like my own) but a condensing boiler will easily achieve ~ 80C (non condensing) with a gain of ~ 7%,
I would definitely try and run on the return target temp of say 40/45C, you can then adjust flow rates etc to give optimum comfort and performance.
Think you are correct re the reading, the silent red 0 at the end confused me.
I also think there is a little rotating mechanical device (outlined with red oval) that you can get a very accurate boiler consumption number from, time it exactly for say 5 revolutions, if it takes say 70secs then the boiler consumption is 5.5 kw.
Or maybe time the red counter for exactly one revolution (1 FT3?)
Thanks, at least that dispels what I was told about the plume being a sign that the boiler is in condensing mode.....would measure the condensate, but it’s all piped in quite secure and insulated, so won’t disturb that.Think you are correct re the reading, the silent red 0 at the end confused me.
I also think there is a little rotating mechanical device (outlined with red oval) that you can get a very accurate boiler consumption number from, time it exactly for say 5 revolutions, if it takes say 70secs then the boiler consumption is 5.5 kw.
Or maybe time the red counter for exactly one revolution (1 FT3?)
That's fantastic, you can now use this to either get a new DAB pump or a new boiler or something in between!.Thanks, at least that dispels what I was told about the plume being a sign that the boiler is in condensing mode.***.would measure the condensate, but it’s all piped in quite secure and insulated, so won’t disturb that.
Re the gas meter, I think the dial marked in orange, is 1/10th of a unit, so each full rotation of the dial circled in green would increase the digit ‘ circled in orange’ by One, IMO
View attachment 47612
Welcome back.
You still have a lot of control over your return temperatures but the boiler may not be happy.
Taking the above.***.flow/return/deltaT, 23C room temp and a TRV...
64/55/9 if you increased the flow temp to 70C then the exact same rad output will be achieved.***.70/48/22 so you are now condensing nicely with a deltaT of 22C .
If you increased the flow temp to 75C then the exact same output will again be achieved ***.75/44/31, better condensing but at the boiler deltaT limit of 30C. (I run my boiler all the time at ~ 70/75 and see these return temps of 43/46C regularly). I'm sure I mentioned these numbers previously??.
Now, if you doubled the size of the rads to give the same output as above then, for the same flow temp of 64C.***..flow/return/deltaT 64/24/40, deltaT 10C greater than boiler limit of 30C.
60/28/32 excellent condensing but marginal deltat for boiler
55/33/22 again outstanding condensing and only 22 deltaT.
SO, to sum up, with existing rads (output) then with a flow temp of 70C you will have a return of 48C and a deltaT of 22C
If you double the rad size, you can have a flow temp of 55C with a return of 33C and a deltaT of 22C.
if a TRV shut back, wouldn’t the heat released from the associated radiator fall ?, or would the flow increase through the remaining radiators, if not wouldn‘t this result in an increased return temperature To the boiler ? If the TRV was fully open, then this would be the same as not having a TRV ???Yes, as long as the rads are controlled by TRVs, if not controlled by TRVs then reducing the flow temp is the only way to reduce the return temp.
Will certainly give that a try, Friday 🤞....running 62C/52-55C/7-10C/5-6KW working well, heating cycles 2-3 times a day when the room stat is satisfied, Hot water heated at same time as heating is on, so not a problem so far. With the two lounge radiators increased from 2784 to 5439 BTUs ( based on 50oC DT, [although I realise mine are 40oC DT]) Each, hopefully will be enough to improve things next winter.Forgot that you have a "smart" circ pump so a much easier method of achieving your output of 5.3kw with reduced return temp.
Your present settings are flow/return/deltaT/Kw, 64C/59C/9C.
If you increase the flow temp to 67C, change from CC3 to CP3, observe the return temp, then change to CP2 and finally CP1, if the pump curves are as I think they are then you should/might get 67C/50C/17C. Downside is you would probably have to return to CC3 to enable the boiler to refire after shutdown. Maybe worth a try?.
I worked most of my life on refineries, where heat recovery was paramount, especially producing 600# steam from furnaces to drive turbines. I love thinking of ways to be more efffcient, but sometimes the odds are weighed against me. I envisaged a system, where a separate cold water tank ( feeding the DHW cylinder, could be preheated, using an other boiler heat exchanger, just before it vents outside, to extract the remaining latent heat, would only need a very small pump, only running when the boiler is on......the ‘heated’ DHW storage tank would be the size needed for a days use of DHW, if it fell low, it would be made up from the main DHW storage tank, would need to be foam insulated also......just a dream......I don't think it's worth the hassle/expense, I have always been skeptical of the actual condensing benefit achieved.
On oil fired boilers, the flue gas temp on a SE boiler is around 230/250C and 80/100c on a HE so a real gain of ~ 6 to8%, I would like to see typical flue gas temperatures for SE/HE gas boilers, I wouldn't expect a SE gas boiler temperature to be as high as that of a oil fired boiler.
But there are lots of ways of skinning a cat, I ran and maintained relatively large 50MW, 45 bar superheated steam boilers and because of the high water temps involved (259C) regenerative rotary air heaters were used to heat the incoming combustion air with the outgoing flue gas and the boilers had ~ 85% efficiency....your next project.
Like thisYou will get particles that will build up in the burner chamber that won’t get flushed through with the condense and will build up to a point where it just blocks the hex and could cause it to split
Pm him I am sure he will have a explanation
Like this
Bit cleaner now 😉I am working on one now as we speak
Says “cost effective “ at £630 I wonder how long it would take to pay back, also for combi boilers only, so no good for me...🤯Products do exist but they are costly. Kop
Hello, there must come a flow temperature that just doesn’t release enough heat to be comfortable, not sure if flow temperature and radiator heat release is linear. Just seeemed to make a difference when I lowered it to 62oC.....no idea if its the same temperature at the TRVs all rads do get hot, so assume that must be the case.....I maybe thinking wrong but how can 2dc make a room feel colder when it’s well above the room temperature
I could understand if the flow temp was 40 but not 60dc you sure you have a flow temp at 62dc at all your trvs ?
interesting stuff 👍 would love to se your spreadsheet, can you attach ?Should also add another bit of info.
If your room(s) should suddenly fall to 10C then the flow/return/output will be
65C/56.6C/7.35kw. 5C roomtemp = 65C/55.6C/8.21kw & 0C = 65C/54.4C/10.6kw.
The most interesting part of all this is that the return temp doesn't change much in any of the above so it looks like any system with fixed flow temp and fixed flowrate will never condense under any conditions except at start up
Can give you a dummy email address that I keep for such purposes.......👍I will try once again but for the past few months havn't been able to attach any, they used to attach no problem previously in zipped form.
We recommend City Plumbing Supplies, BES, and Plumbing Superstore for all plumbing supplies.