Vaillant EcoTec Plus 630 dT

[John Carroll]

The boiler flow/return dT can be set in the above by changing  a few parameters to set the dT to between 10C and 20C, see attachment.

However this does not seem to work for someone I know, it worked to a fashion on CH only but not in HW mode (this isn't a big deal though)

The dT was set to its max, 20C in all the examples, below.

The best result (briefly) was a dT of 17C with flow/return temps of 64C/47C, pump speed 58%, next best gave 64C/50C, dT 14C, pump speed 64%, and on HW (cylinder), 64C/60C, dT 4C, pump speed 80%.

Can someone throw any light on this or if they have a EcoTec Plus try these parametrs to see wht results they get, this boiler is just 1 year old.

D.170 is set to 3, which is temperature spread control or dT.

Vaillant EcoTec Plus 630 dT.docx

[JohnMo]

dT is a combination of how much heat can be taken away compared to how much is being generated by the boiler. If your radiators can only transfer 4kW (dT between them and the room for example) and you are generating 16kW something has to give and it's dT. Reducing flow may cause the boiler to short cycle, increased flow will reduce dT.

 

The lower the flow, more heat is extracted from the water flow for a given heat input.

 

On the cylinder with a small coil and high flow rate your dT is always going to be small.

 

Bottom line is what are you trying to achieve?

[John Carroll]

Its not my boiler I have a oil fired boiler.

 

It was running (CH only for first 2 tests) at a modulation level of 4, I think it goes to 5 max?, 16 rads, all fully open so even with flow/return of 64C/44C, dT 20C will still give a rad(s) output of 60% so no way is this boiler output down to minimum, a dT of 20C with a target temp of 64C gives a return of 44C and a nice bit of condensing. if the boiler can achieve this dT of 20C then far easier than spending hours balancing rads to achieve it?, I would say its a excellent feature if it works.

 

[JohnMo]

6 minutes ago, John Carroll said:

If the boiler can achieve this dT of 20C then far easier than spending hours balancing rads to achieve it

Doesn't mean you don't need to balance, that is still needed. Balancing is required to ensure each radiator works as it should, without that the water could just circulate through a single radiator, boiler gives you dT 20, but house is cold because you have bypassed most the radiators.

 

Still not sure what you are trying to do?

[John Carroll]

This is what someone is trying to do (if Vaillant can sort out this dT control problem).

There is a rad(s) demand of 4kw and a UFH demand of 7.5kw, a boiler flow temp of 60C is required to give the required rad output, this means the boiler return is 52.2C, 7.8dT, not too bad, but just about condensing, this is with a boiler circ pump flowrate of 21LPM, if the boiler dT was increased to 16.5C, then the boiler return temp should be ~ 43.5C with quite considerable condensing, this is with a boiler circ pump flowrate of 11.5LPM, if my calcs, attached, are correct.

LLH + Rads and UFH Rev0.xlsx

Edited November 26, 2024 by John Carroll

[JohnMo]

2 hours ago, John Carroll said:

boiler return is 52.2C, 7.8dT

So that gives a mean flow temp through the radiators of 48.3 degs.

 

If you flow at 52.2 and have a return of 43.5, you heat output will drop by a big chunk, as the mean flow temp drops to 43.7. So not sure that will work

 

Big gains for not condensing to condensing with the return below 54 degs. Small margins after that.

 

You only have 4kW of water flow going to the radiator and 7kW to the UFH, so the return from the UFH will dominate the return temp.

 

Think I would be more interested in getting rid the LLH

[John Carroll]

The rads flow/return are 60C/50C, mean of 55C, so a, (55-20), T35 Rad, which will emit (35/50)^1.3, 63% of a T50 rating, irrespective of what is going on elsewhere, you then have ( UFH), 3.84LPM@32C mixing with (rads), 5.73LPM@50C to give 9.57LPM@42.8C goint to LLH secondary but because the boiler circ pump is circulating 21LPM then the primary side recirculation of 11.43LPM@60C is mixing with that returning 9.57LPM@42.8C, you end up with a boiler return of 21LPM@52.2C.

As you allude to,  a LLH can becomes a DLH, (Dead Loss Header?) unless the primary and secondary flows are equal., hence the desire to get that dT control working, I have read of other conventional installations (no LLH) where that boiler doesn't  achieve this either.

[JohnMo]

Just had a read of the manual and notice it states with LLH you have to run at fixed speed, but there are plenty of speeds to choose from. So flow rates could be lower. Have you adjusted?

 

 

[John Carroll]

Yes John,

The fixed speed is settable, 50% to 100%, and a few tests showed a (vaillant) flowrate of (converted from LPH) 24.3LPM at 100%,and 11.53LPM at 50% which makes good sense,  since flow is directly proportional to speed. The  dT tests did nothing, there is also a constant pressure option, settable between 100mbar and 400mbar but the tests were inconclusive as 400mbar gave ~ 23LPM but 150mbar didn't produce a much lower flowrate whereas it should theoretically, have been, 23*sqroot (150/400), 14.1LPM.

Edited November 26, 2024 by John Carroll

[John Carroll]

 

Some  one might do a few tests on one of these boilers, @ j_s ?

 

The Boiler is dispatched with (Hydraulic Operating Mode) D.170  set to 2 (dP constant) and D.171 (target pressure value set to 200)

If so, or whatever mode your boiler is on, Note

D.015 (pump speed), D.029 (flow rate), D.040 (flow temp), D.041 (return temp) and Target Modulation.

Change D.170 to 3 (Spread dT), Set D.172 to 20C (Target spread value), take another set of readings after say 10 minutes.

If using Weather Compensation, switch it off  if possible, set the Boiler Target Temp to 62C , wait for say 5 minutes after target temp is reached and take another set of readings, (D.170 set to 3)

 

Please state if a LLH is installed or not.

 

Edited January 6 by John Carroll

[JohnMo]

@John Carroll you have not tagged @j_s correctly. Type @ then carry on typing with no spaces and select from drop down that appears

[John Carroll]

4 minutes ago, JohnMo said:

@John Carroll you have not tagged @j_s correctly. Type @ then carry on typing with no spaces and select from drop down that appears

Thanks John @JohnMo but too late as I've exceeded my 30 minute window to edit, I know how to it now though!!.

[burgessl]

@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%

 

[j_s]

I will try and get it done but no promises as need to get a load of diy stuff done, not so fun with these cold temps currently. I'm not sure how to change the settings or see the return temps, modulation, pump speed etc. 

[John Carroll]

12 minutes ago, burgessl said:

@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%

 

 

Thanks a million @burgessl, 

 

What was D.172 set to in the 3 tests?, if it was 10C, or 5C in the first test and 10C in the other two tests, can you do one/two more at at a dT of 20C with the flow temp at 62C.

[burgessl]

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. 

[marshian]

Don't have a vaillant boiler but I'm liking the deep dive on settings and the experiments - great stuff guys

 

Commenting so I can add the thread to content I follow

[John Carroll]

3 hours ago, burgessl said:

@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%

 

 

Fantastic info. just whats needed.

 

Won't go through the dreary calcs but test 1 shows 3.6kw & 4.38kw Mod.calc vs flow/dT calc). flow/dt calc +20%

test 2 16.2kw vs 18.07kw. flow/dT calc + 11.5%

test 3 11.7kw vs 12.6kw. flow/dT calc +8%

as with the "problem" boiler the dt/flow calc is consistently higher than the modulation output calc but this flowrate is probably derived from the smart pump power and calculated efficiency but at least is reasonably accurate enough to see it changing with pump speeds.

 

The second test shows that the dT of 19C is almost at the requested dT but this might just possible  because the system was still settling down with that huge change.

 

The third test is the most interesting because its output is almost directly proportional to your steady state test 1 where the output was 3.6kw, at this test the flow/return temps were 37C/32C, assuming a room temp of 20C then you had (37+32)/2 - 20, a T14.5C "rad"

the third test with flow/return temps of 62C/49C, gives a (62+49)/2 - 20, a T35.5 "rad" which will result in a factor of (35.5/14.5)^1.3, 3.203, to give a output of 3.203*3.6, 11.53kw which is almost spot on with the mod. output of (0.39*30),11.7kw.

 

The reason for this rigmarole is just to be satisfied that the system had settled down, BUT the target dT of 20C was not achieved, it was "only" 13C, one could say why not, maybe the answer lies (even though I'm doubtful) in that the spread dT is limited if the pump dP falls to 100mbar (1.0M) as shown by  D.173 (minimum pressure level while in spread dT).

Now, the circ pump head is 5.5M as advised by Vaillant tech to me, I am skeptical of this and would venture its more likely to be nearer a 7M pump, IF its a 5.5M pump then because dP is proportional to speed squared, the dP in test 3 was only 5.5*0.35^2, 0.673M (67.3mbar), IF its a 7M pump then the dP at 35% speed is 7*0.35^2, 0.858M (85.7mbar) getting close to the limiting 100mbar, however I just can't see a dP of 0.67M or even 0.86M circulating 13.92LPM (836LPH) through the boiler HEX and your system, with a LLH, yes, as the only resistance to flow is the boiler HEX

However, with your help we can figure out if the dT is limited by this "100mbar"

You might sometime change D.170 to 2 (dP constant) and change D.171 to its minimum selectable dP of 100mbar, wait a few minutes and note the pump speed and flowrate, that will reveal a lot.

 

Even on fixed speed mode with D.170 set to 4, D.175 (the pump speed demand) can't be driven below 50% on this boiler, again, sometime you might see if yours is likewise.

 

 

 

 

 

 

 

 

 

 

 

Edited January 6 by John Carroll

[John Carroll]

I see you have a 625 but I think the the tests are still valid ie test 1 mod output is 0.12*25, 3.0kw, test 3 mod output is 0.39*25, 9.75kw, calculated output, 3.203*3.0, 9.6kw.

[John Carroll]

The problem (30kw) when set to dP (constant pressure) below set to 100mbar (1.0M) still maintained 83% pump speed, which, assuming a Vaillant advised installed 5.5M pump means that the pump head at 83% is 5.5*0.83^2, 3.79M or 379mbar despite a requested head of 100mbar.               The pump flow when changed to fixed speed and set to its lowest speed of 50% was a corrected 692LPH, the  pressure loss through the boiler HEX is 2.6M at its rated flow of 1290LPH so at a flowrate of 692LPH is 2.6*(692/1290)^2, 0.748M, 50% pump speed is a pump head of 5.5*0.5^2, 1.38M, 138mbar which approximates to the 0.7M at 692LPM through the boiler HEX, so no reason whatsoever IMO as to why the pump speed wasn't driven down to ~ 50% on dP control, the same should apply on Spread dT control, it just will not drive the pump speed down to at least 50% which we know is ~ 138mbar, well above the 100mbar minimum allowed.

This is why I'm interested in the results from another boiler, without a LLH, set to dP control at 100mbar to see how low the pump speed falls to.

 

D.170 option 2 (Bypass, dP constant): D171 dP 100mbar

         

           Target modulation = 63% = 18.9kw

               D.015 = 83%

               D.029 = 1,576 l/h

               D.040 = 62C

               D.041 = 50C = 21.99kw ( X 1.164)

Edited January 7 by John Carroll

[John Carroll]

It seems the both these pumps don't perform as per spec on either constant dP or Spread dT modes.

@burgessl pump above was showing flow rates of 700 to 1200LPH at a the default setting of 200mbar (2.0M) on the default hydraulic mode of dP constant.

I have very accurate flow readings for a 6M (Wilo) circ pump running at both 6M and 2.0M above, and its quite easy to see that there is no residual head remaing after passing through the boiler HEX to push water through the rads at a flow rate of 1075LPH, pump head is 1.85M and the HEX pressure loss is 1.85M, if the pump was running at its full speed and head of 6M then the pump head at 1075LPH is 5.05M so residual head is 5.05-1.85, 3.2M, quite capable of circulating 1075LPH through rads etc IMO.

Likewise the dT test above shows a pump speed of 35% and a corrected flow rate of 645LPH (from indicated 836), the pump head at 35% speed is only 0.74M, the HEX pressure loss at 645LPH is 1.04M, it might circulate ~ 200LPH through the rads if the system resistance is low enough.

Residual Pump Head. burgessi.xlsx

[burgessl]

@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

[John Carroll]

14 hours ago, burgessl said:

@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%      =0.34*25, 8.5kw

Target Flow: 62

Actual Flow: 62

Actual Return: 46

Flow rate: 477 l/hour   = 477*(62-46)/860, 8.87kw

Pump speed: 21%

 

Fixed pump stage 50%

Modulation:  32%       =0.32*25, 8.0kw

Target Flow: 62

Actual Flow: 62

Actual Return: 48

Flow rate: 505 l/hour  =505*(62-48)/860, 8.22kw

Pump speed: 50%

 

I have to admit I haven't had a time to fully digest your posts yet sorry

 

Thanks for that,

 

You can see from the above that the flowrates and boiler outputs both on dP control at 100mbar (should = ~ 43% pump speed) and 50% fixed speed control are roughly the same, or at least quite good enough to show that the dP conrol mode is working quite reasonably well.

 

The problem boiler works perfectly well in fixed speed mode but not on dP control, see example  data, below, the pump runs at 83% and higher at a dP request of 100mbar, the pump speed should be down around 43/50% with a flowrate of 950LPH, the flowrates will be far higher than yours at any given pump speed because of the LLH where the only pressure loss is through the boiler HEX plus a very very small loss through the pipework to the adjacent LLH.

 

D.171 = 100mbar,  (dP control)

               Target modulation = 63%   = 0.63*30, 18.9kw

               D.015 = 83%

               D.029 = 1,576 l/h                 = 1576*(62-50)/860,21.99kw

               D.040 = 62C

               D.041 = 50C                   

 

Edited Monday at 23:48 by John Carroll