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Another question, I have watched the pump running on both the kitchen (troubled) and laundry manifolds, individually. Correct me if I’m wrong but should the kitchen manifold not run at less RPM than the laundry manifold that had 50m flow and return pipe? The kitchen manifold runs in 32mm cooper from boiler (5m) until it tees off for manifold then it runs in composite 26mm for 2 metres till it joins manifold.
Doesn’t the boiler pump only control the flow and return from the manifold and the manifold pump controls the flow and return in the manifold circuits?
Will reply to manifold pump later.Ok will do thanks John. You said in a previous post the boiler pump is normally around .4 bar, 4m head, if this external pump is set to 1.35 bar 13.5m head is this an issue with the expansion vessel, as the expansion vessel charged to one bar allows the system a static head of 5m. View attachment 76721
If you are referring to the 18L (white) EV, it appears to be connected to the Cylinder cold water inlet? (with blue isol valve), post #87.
Will reply to manifold pump later.
Re boiler external pump, if the EV is connected into the suction side of the pump, the pump discharge pressure should be the EV pressure+the pump head, in your case, 1.3bar+1.35bar=2.65bar, if the EV is connected at the pump discharge then the pump discharge pressure will be the same as the EV pressure, in your case. 1.3bar, the pump suction should then be the EV pressure-the pump head, 1.3bar-1.35bar=minus 0.05bar or minus 0.5M which means part of the system can be running under negative pressure, not desirable as air can be drawn in, in practice boilers (especially Gas) often have their EVs connected into the discharge side but with a EV pressure of 1.3bar and a pump head of say 0.7bar will still result in a positive pressure at the suction side, 1.3bar-0.7bar=0.7bar or 7M.
Its may cause erratic operation of the UFH manifold TMV because you have hot water at high pressure on one side of the TMV and much lower pressure on the other side coming from the cold manifold return.
(BOILER FLOW TEMP SET TO 65)Can you give me your observed/estimated readings for the two UFH manifolds, ie, boiler/manifold flow temp, manifold(s) flow (mixed) temps & return temps & the total manifold flow rates.
Also a rough idea of the total rated rads output and the actual/estimated dT.
Does that pump display only the RPM in that box?, ie some can display the calculated flowrate if selected.
The boiler will not get any higher than 48 degrees with heat only on kitchen manifold, I have again just now watched it SP is 65, flow no higher than 48 and boiler has been running for 48 mins continuously. I am totally stumped as to why the boiler does not perform when heating kitchen manifold.OK here are my numbers.
Why is the boiler temp so low at 48C (SP 65C) assuming a heat demand of "only" 19.88kw for the kitchen manifold??.
You can see why the Blr pump speed is far greater on the kitchen manifold vis the Laundry manifold due to the different flowrates required, 21.92LPM vis 4.71LPM respectively.
The very low pump speed on rads only at 891LPM for a flowrate of 19.23LPM is indeed puzzling, would have expected it somewhere up to 1700/1800 RPM based on the blr circ pump speed of 1870 RPM required for the kitchen manifold with its blr circ pump flowrate of 21.92LPM.
(BOILER FLOW TEMP SET TO 65)
Kitchen ufh manifold (troubled)
Boiler/manifold flow temp 48 c
Manifold mixed flow temp 45
Manifold return temp 35
Total flow 28.5 LPM
Blr circ pump flowrate, 21.92LPM (Manifold output, 19.88kw) Pump RPM 1870.
Laundry manifold
Boiler/manifold flow temp 70 c
Manifold mixed flow temp 45
Manifold return temp 35
Total flow 16.5 LPM
Blr circ pump flowrate, 4.71LPM (Manifold output, 11.50kw,) Pump RPM 1080.
Total Radiator output 19kw
DT across Rads 12 degrees
Flow 70
Blr circ pump flowrate, 19.23LPM (Rads output, 16.10kw, based on mean rad temperatures)
Pump RPM 891
Return 58
It’s derated to 26kw.The only logical explanation is that the demand is > than the boiler output?. I think you said somewhere that the boiler is actually derated to 23kw so not far away from the nearly 20kw kitchen demand, you might consider reduving the TMV setpoint to 38/40C, this should result in a reduction in the heat emitted by the loops and allow the boiler to get up to its SP temperature.
I will look up the boiler output nozzle rating and see what output it gives at 14.0bar.
It’s derated to 26kw, using a danfoss .55 80s, air setting 3.5.The only logical explanation is that the demand is > than the boiler output?. I think you said somewhere that the boiler is actually derated to 23kw so not far away from the nearly 20kw kitchen demand, you might consider reduving the TMV setpoint to 38/40C, this should result in a reduction in the heat emitted by the loops and allow the boiler to get up to its SP temperature.
I will look up the boiler output nozzle rating and see what output it gives at 14.0bar.
I thought that was the case. Does the kitchen manifold need a bypass on it?Pipe (friction) losses are proportional to the square of the flow, so the losses at a flowrate of 4.71LPM are tiny with the piping sizes you have ~ only 5 to 6% of the losses at 20LPM. Your rads have no problem with a circulation demand of 19.23LPM.
I remember the plumber telling me if the pumpset was changed a bypass would need to be fitted, I'm not sure why )Why does the kitchen manifold require a bypass??
What was the laundry manifold (mixed) temp? and was the manifold flowrate still 28.5LPM?.
If the boiler/manifold return was 43/44C then the manifold temperature had to be 6C to 8C higher so TMV not going much at a SP of 40C??
if only our kitchen one would perform nicely, yes will run that test now.Must go out for a hour or so, will revert later, can you run that test on the kitchen manifold.
The Laundry manifold TMV is performing perfectly as you can see by your findings, below, with mixed flowtemp of 45C (boiler at 70C) , there is not a lot of water returning to the boiler, only 4.,71LPM?.
Laundry manifold
Boiler/manifold flow temp 70 c
Manifold mixed flow temp 45
Manifold return temp 35
Total flow 16.5 LPM
Blr circ pump flowrate, 4.71LPM (Manifold output, 11.50kw,) Pump RPM 1080.
Ok so here goesif only our kitchen one would perform nicely, yes will run that test now.
So should we put a bypass in somewhere? there was one on the side of the boiler teed into the flow and returning back into the bottom of the boiler ? The nozzles they have had in this boiler are 0.55 80 s 2.11kg/h and a .50 80s 1.87 kg/h. Thank you for your spreadsheets they are very informative.The above gives a manifold demand of 21.85kw so the boiler output must be there or there or there abouts the same since it can't reach its SP and cut out, I suppose the manifold temp of 48.6C isn't bad control since we don't know how accurate the TMV SP index is, you might reduce it to 30C sometime to see reduced manifold output and boiler cut out
For interest, you can see the bypass flow required to increase the boiler return temp from 37C to 45C.
The position of the EV connection is effectively into the pump suction in your boiler and it the new original seems to be into the pump discharge with the pump pumping into the return, probably OK in both cases.
Boiler return 37C (no bypass)
View attachment 76763
Boiler return 45C (with bypass)
View attachment 76762
Its taking 1 hour to get the floor temp up 3 degrees differential in the kitchen and it has a cycle time of approx 3 hours.I wouldn't have it as my top priority just now but can think about best way to achieve it, would be inclined to try a "Tapstat" with the sensor on the boiler return set to 45C (or whatever min return temp required).
How long is it taking the UFH to get the room (kitchen?) temp up their desired temp, at the moment the room/ambient dT isn't particularly bad, so roomstat should be cycling fairly often?, and the rooms with rads??.
Do you intend to increase the boiler output??.
The installed blast tube should be as recommended, I have a feeling that the reason for the small nozzle with the extremely high pump pressure is to get the emissions right, a, say, 0.65 nozzle with a more modest pump pressure of 10bar + the T3 should give the same boiler output and probably less flame impingment on the baffles.
If we haveIts taking 1 hour to get the floor temp up 3 degrees differential in the kitchen and it has a cycle time of approx 3 hours.
Yes I intend to increase the boiler output, but I'm unsure whether 35kw is enough output for UFH, & Rads. I will also get blast tube changed to instruction manual specs.
You are very knowledgeable. Thank you.Yes, but there are lots of ways of skinning a cat, if the kitchen has a cycle time of 3hrs, 1 hr on time so kitchen average requirement is 21.85x0.33=8.3kw, ideally the UFH should give this output continuously and the manifold output can be reduced by various means, reducing the mixing temperature for example so assuming Laundry similar at 11.5x0.33=3.8kw, then continuous UFH demand is ~ 12.1kw, the rads might cycle in a similar fashion, so you may well find that 35kw output is quite sufficient.? You measured your oil consumption at ~ 23LPD or ~ 10kwh/hr so not a mile away from the above?.
Oh yes forgot about the PRV valve. So you think we should put a pump set on the laundry like the kitchen one? (Instead of the one attached)I would suggest replacing the boiler PRV (safety valve) as well, it may be lifting before 3bar.
The laundry manifold seems to be performing spot on, it gives a mixing temp of 45C with a boiler temp of 70C, what is the TMV setting index?, you could reduce that by say 5c to test that the TMV is working OK.
Have you the spec on the original circ pump model etc.
Laundry manifold
Boiler/manifold flow temp 70 c
Manifold mixed flow temp 45
Manifold return temp 35
Total flow 16.5 LPM
Blr circ pump flowrate, 4.71LPM (Manifold output, 11.50kw,) Pump RPM 1080.
NO, what I said is that this TMV/pump set seems to be working perfectly well even though I would like to know how it "works" (see queries in attached that you can answer). Can you see what the TMV is set to just now?.Oh yes forgot about the PRV valve. So you think we should put a pump set on the laundry like the kitchen one? (Instead of the one attached)
I don't think this will work because the circ pump is on the flow so the boiler return pressure is > than the flow (where it leaves the boiler) so the bypass flow will be the wrong way?.This is the pump they moved from inside the boiler, also they have attached this pipe between flow and return. Do you think I should turn this on to get retune temp up?
Yes, IMO, so just reduce this (kitchen) TMV setting to say 30C or whatever is required to get the mixed flow temperature down to say 35C/38C.So the only explanation we have as to why the boiler doesn’t reach serpoint when heating the kitchen manifold is because the manifold output is > or = to the boiler output?
The laundry TMV is set to 45 c.NO, what I said is that this TMV/pump set seems to be working perfectly well even though I would like to know how it "works" (see queries in attached that you can answer). Can you see what the TMV is set to just now?.
If it's working OK why change it?.
I don't think this will work because the circ pump is on the flow so the boiler return pressure is > than the flow (where it leaves the boiler) so the bypass flow will be the wrong way?.
Yes, IMO, so just reduce this (kitchen) TMV setting to say 30C or whatever is required to get the mixed flow temperature down to say 35C/38C.
So the SP is 45C and the actual is 45C= perfect control, don't dream of changing it.The laundry TMV is set to 45 c.
Turn it down to 30C, see what effect it has, if any.I have this morning turn the kitchen TMV down to 38 c and mixed water is still getting to 46 c. I am wondering if the pump pressure and speed of water is literally seeping through the valve.
Yes, that might work, but don't really know its purpose, would prefer to eventually see a temperature controlled one installed in the correct position.Below is a better pic of the manual bypass, it actually tees of the flow before water even gets to 2 way valve and joins into the return pipe from DHW cylinder, which then tees into UFH return pipe.
Sorry for all the questions, hope your brain is not as confused as mine
The kitchen pump had started leaking and they recommended this, as the same as the laundry is obsolete now.So the SP is 45C and the actual is 45C= perfect control, don't dream of changing it.
Turn it down to 30C, see what effect it has, if any.
I would think something wrong with the TMV as the laundry is under similar working conditions and working perfectly, why was a decision made to replace them with this kitchen type? which ironically is not working.
Yes, that might work, but don't really know its purpose, would prefer to eventually see a temperature controlled one installed in the correct position.
Just crack it open gradually until it raises the return temperature to 45C or so.
You might also have a look at this and comment.
Yes correct, hot flow pipe from boiler.Just crack it open gradually until it raises the return temperature to 45C or so.
You might also have a look at this and comment.
I cracked open that manual pass valve and you wouldn’t believe it the boiler got up to temperature (well boiler step point was 60c but boiler flow reached 72c) and the expansion vessel off the hot water cylinder was dripping. So I believe the expansion vessel in the boiler is either not working or to small when running the kitchen UFH manifold.Yes correct, hot flow pipe from boiler.
The other pipe is the return to boiler/cold return.
the little pipe on the end of the manifold, is an unused pipe (yes cowboys instaledl our system)
Attached is diagram on how isotherm is suppose to work
Yes expansion valve on HW cylinder was dripping, with that bypass valve open hot water was feeding down the pipe to where the EV is on cylinder. Nothing else was calling for heat other than Kitchen UFH with manual bypass open. Boiler pressure was 1.5 bar, pump was 1.35 bar, flow temp was 72 degrees. (Hope that makes sense)Do you mean the expansion valve on the HW cylinder is dripping, if so, this, or a failing HW cylinder EV has got nothing to do with the boiler EV or PRV, what is/was the boiler pressure gauge reading when this dripping occurs?.
Ok so you get a burner output and a boiler output from one nozzle calculations?If that bypass valve is feeding HOT water into the HW cylinder then it will have to be from the HW cylinder hw outlet which will be at higher pressure when the cylinder is heating or is hot with no HW draw off, if tied into the boiler system primary system flow pipe it cannot feed hw as the primary/boiler system pressure is only 1.5bar. If it was connected from the cold mains then that will lift the cylinder expansion valve but the pipe would be cold.?
Nozzle Sizing: From below. a 0.65 nozzle will give a burner output of 31kw @ 12.5bar which will be 31*(14/12.5)^2, 32.81kw @ 14bar, a boiler output of 28.87kw @ 88% boiler efficiency.
Your present 0.55?? nozzle will give a burner output of 26kw @ 12.0bar which will be 26*(14/12.0)^2, 28.10kw @ 14bar, a boiler output of 24.73kw @ 88% boiler efficiency.
Thank you for the calculations they are very handy.Yes, the table gives (presumably) burner output, the only assumption that will marginally affect the boiler output is its efficiency so 85% to 92% should cover it, the calculation for pressure is universally used, ie flow is prop to the sq.root of pressure, I should have shown that as ^0.5 and not ^2, but I did use ^0.5 in the calculation.
Can't really comment on that by pass except to suggest finding out exactly where the connections are teed in.
Ok, will do. I’ll get back to you.This Laundry Manifold/TMV is a mystery to me as all the indications are that the return temperature to the boiler is the mixed flow temperature but havn't figured out if this is thermodynamically possible.
You might please take the (4) temperatures where indicated and also take the return temperature to the boiler; at the boiler.
View attachment 76807
Boiler set point 60This Laundry Manifold/TMV is a mystery to me as all the indications are that the return temperature to the boiler is the mixed flow temperature but havn't figured out if this is thermodynamically possible.
You might please take the (4) temperatures where indicated and also take the return temperature to the boiler; at the boiler.
View attachment 76807
Oh sorry, I’ll check againSorry for confusing you, its the temperatures at 1,2,3&4 in this attachment I would like.
Oh sorry,Sorry for confusing you, its the temperatures at 1,2,3&4 in this attachment I would like.
Awesome, sorry have been away for back tomorrow and then I’ll have temps. Thank you.Have added another one below, point 5, so measurements at points 1,2,3,4,5. (thanks for your patience)
Ok so I have checked all temperatures and what a shambles, they areOh sorry,
Awesome, sorry have been away for back tomorrow and then I’ll have temps. Thank you.
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