Grundfos Alpha 2 AutoAdapt is slow

[Marck C]

Hi folks be glad of some help with this as its puzzling me.🤔

I have an Alpha 2 15-60-130 pump serving 12 Rads with thermo valves and Hot Water cylinder. The boiler is an Alpha CD18R

Since I had another rad installed downstairs I've noticed the heating pump has been noisier than usual ie running at full bore... annoying when it comes on during the early hours to start the days heating.

The engineer had left it set to III which runs at 45W. It gets the job done but at the cost of the noise. Problem is I dont know what the setting was before. When I put it onto autoadapt the rate drops down to 9W which seems way to slow to get all the rads piping hot. I've found the best compromise is to use the other Proportional Pressure setting on full which provides around 35W and is ok noise wise, but still feels excessive and not very energy efficient

Since it has an autoadapt feature i'd like that to be working for me but it just doesnt seem to give it enough pressure.

So two questions

Anything else I could be checking for?

What power wattage would you expect to see for my system?

 

[John.g]

Hi Marck, you can forget auto adapt as I've never seen anyone saying that it works, most, like you say that it runs at 9W which is completely useless. Strangely enough, the only pump that someone told me was running OK in "Auto" was a Tucson 6M pulling 23W which is quite acceptable.
A pump output of 20/25W is a reasonable power output to satisfy your 12 rads, I also have 12 rads and with my pump (Wilo Yonos Pico) set at a PP setting of 4.1M pulls between 14 and 21W depending on TRVs positions, I can set my pump on PP (or CP) settings incrementally in 0.1M steps, if I set it to your PP3? setting of 4.5M then it will pull around 31/33W, similar to yours. Unfortunately the Alpha2 pump has a big gap between the PP settings so if you were to set yours to PP2 which is 3.0M then you may find that is too low, you can try it (with all rads "full on", if its below ~ 14W then a bit weak IMO to satisfy all the rads, unfortunately, the CP settings are the same as the PP settings and the fixed speed settings are again either too low or too high.
But, its only a button press, would suggest trying PP2, CP2 and constant curve 2 (fixed speed 2) and jot down the pump power for each, you can then make a decision based on what I suggested above and if you don't mind, post back your results.

One other thing I notice is that your pump was pulling 45W at fixed speed 3 whereas according to the Alpha2 pump curves, the max pump output is limited to 35W.

 

[Marck C]

Hey John.g thanks for your quick and detailed response its just what I needed.. 👏 I will have a look at the settings you suggest in the morning and post back 👍
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Ok looked at it this morning at the heating was starting for the day.

I ran through the settings and this is what I got...
III - 45W
II - 19W
I - 6W
AuotpAdapt went up to 32W but quickly dropped to 12W
PP1 - 10 W
PP2 - 14 W
PP3 - 20 W
PP4 - 35 W

I might try it on PP3 for a while to see how it heats the rads, but PP4 seems to give the best Performance/Noise ratio for now.

 

[John.g]

There is no PP4 setting so you might just see which setting is giving you 35W, IF PP3 is actually the setting pulling 20W then that may satisfy your requirements, it might be easier to just run through the PP and the CP settings again, PP settings depict a radiator and the CP settings depict a (UFH) pipework.
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Should have said PP mode depicts a sloping pump line and CP mode is a horizontal line.

 

[Marck C]

Hmm🤔 Confusing. I don't see the icons you mention o my unit. I've attached a photo of it... the four settings on the right are the ones i'm assuming are PP settings

 

[John.g]

I've "found" your pump I think, see attachment. You have three constant curve settings (left hand LEDs...I,II,III) and two PP & two CP settings, (right hand LEDs.....PP1,PP2,CP1,CP2). I have taken your readings and edited them below, I have also added the actual flows using the pump curves, you can see that CP2 gives, as you say, probably the best option but maybe worth giving CP1 a go as well. Once again Grundfos seem to provide, IMO, very poor settings but I think they are improving this with their new models.
For example, the three constant curves, which everyone in the world are familiar with are 1M,3M&6M, practically every other manufacturer would provide 2M,4M&6M, if you had the 4M setting available then you would run at ~ 25/27W which would have been be a perfect setting. Also the two PP settings of 1M & 3M are very poor as too low, should be ~3.5M&4.5M.
The CP settings of 3M & 4.5M are, again IMO, very good.
Auto Adapt......forget it.

III - 45W (6M)
II - 19W (3M)………….3.0M & 11.6 LPM
I - 6W (1M)
AuotpAdapt went up to 32W but quickly dropped to 12W
PP1 - 10 W (1M)
PP2 - 14 W (3M)……...2.0M & 10.3 LPM
CP1 - 20 W (3M)……..3.0M & 11.7 LPM
CP2 - 35 W (4.5M)......4.5M & 14.67 LPM

 

[Marck C]

Hi John.g You are a legend!!! You're help has made a massive difference. Thanks so much, its very much appreciated. That makes perfect sense now! Iv'e just looked in on the pump and it was actually pushing at 27W on the CP2 setting for mid-day. That kinda sounds like where I'd want to be. But having said that I have changed it to CP1 and (it went to 20W) to see how it goes for a while. I will leave it on that for a day or so and see if I get a noticeable change in temps etc...

You've been immensely helpful 👏👏👍

I will post back on my final conclusion in a day or so.

 

[Marck C]

Ok so (using the CP2 setting @ 20W) this morning the house reached temp fine by the time I got up. When all the rads were cold I turned the heating up a few degrees and within 10 minutes they had all reached a good (hot to touch) temperature.

So I'm going to stick with the CP2 setting..

Thanks again for your help John.g

 

[John.g]

CP1 is 20W not CP2 which was 35W...so which one are you on?? fixed speed ii also gives 19/20W.

 

[Marck C]

Ok so (using the CP2 setting @ 20W) this morning the house reached temp fine by the time I got up. When all the rads were cold I turned the heating up a few degrees and within 10 minutes they had all reached a good (hot to touch) temperature.

So I'm going to stick with the CP2 setting..

Thanks again for your help John.g

Apologies for the typo in my last... Its CP1 @ 20W that i'm finally sticking with NOT CP2 (thanks for the prompt John.g)

 

[John.g]

Thanks Marck, just one other test that I meant to ask you to carry out for the following reason.....
When I run my system in CP mode at 3M like yours, I also get 19/21W (Cyl+Rads). Cyl only:16W, Rads only: 20W which is OK but when I run Cyl+Rads I still only get 20/21W, the same as rads only which I find strange as both systems seem to get adequate heat.
When you get time, you might run your system as above, and note the readings, a minute or two on each will be plenty, thanks.

 

[Marck C]

Thanks Marck, just one other test that I meant to ask you to carry out for the following reason...
When I run my system in CP mode at 3M like yours, I also get 19/21W (Cyl+Rads). Cyl only:16W, Rads only: 20W which is OK but when I run Cyl+Rads I still only get 20/21W, the same as rads only which I find strange as both systems seem to get adequate heat.
When you get time, you might run your system as above, and note the readings, a minute or two on each will be plenty, thanks.

I ran the tests With the same results
Cyl + Rads i get 21W
Cyl only 16W
Rads only 20W

Hotwater is heating fine and as I mentioned before all my rads are getting nice and hot in quick time. Hope this was useful to you

 

[John.g]

Uncanny, how both systems are identical, I can't figure out why there isn't any change in the readings/actual flow, I run mine normally on a PP setting of 4.2M and the power certainly changes when the rad TRVs close in and it varies from 18/20W to as low as 14W but gives exactly the same power readings (as in above tests) on the same tests which again proves that the total flow rate is unchanging.

 

[Marck C]

Uncanny, how both systems are identical, I can't figure out why there isn't any change in the readings/actual flow, I run mine normally on a PP setting of 4.2M and the power certainly changes when the rad TRVs close in and it varies from 18/20W to as low as 14W but gives exactly the same power readings (as in above tests) on the same tests which again proves that the total flow rate is unchanging.

OK first of all i'm gonna pre-empt this by noting that i'm not technically knowledgeable about pumps and systems, so i can only try to apply some basic logic to this... If CP 1 is designed for systems without TRVS ie underfloor heating, isnt what's likely to be happening that... as the TRVS open and close the power remains relatively constant whilst the resulting pressure will vary? My pump will only show power figures (ie W) but I think I saw that some can show the pressure figures. So if you use a CP setting on a TRV system wont the pressure start varying but not the power?

Or is that way off point? or am I just showing how much of a numpty i am?

 

[John.g]

Nothing wrong with your thinking, the pump doesn't know or care what system it's on and all its doing is changing the speed up or down to keep the PRESSURE constant, so opening/shutting zone valves and/or TRV throttling should be reflected in the power requirement. If you were to throttle in the discharge valve on your pump you will see (or if not, I will be very surprised) the power falling to its minimum,13W when the valve is fully closed (no flow) See page 23 of the attached pump in one of the posts above. If you had the pump pumping out of a tank with a valve on its discharge to drain, then, depending on the valve opening, the pressure will be constant at 3M but the flowrate will change from 0 LPM/13W to a max of 35LPM/42W. That's my reading of it at any rate. I can only think that the total pipeline/rads/HWC coil losses remain the same so the flowrate remains the same but I find that hard to believe, someone might provide the answer.
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The plot thickens or maybe becomes clearer.
When I installed my "smart" pump in 2018 I took a lot of readings and came across them just now while looking for something else.
With just ONE (any one) rad in service (3M CP) the pump pulls 14/16W ~ 5 LPM, almost exactly the same as the HWC coil on its own and with all rads in service (with all TRVs fully open) 20/21W as above which = a flow rate of ~ 11.5 LPM, so each rad (think of them as the rungs of a ladder) will flow ~ 0.94 LPM, my rad sizes average 1.25 kw so this gives a deltaT of 14.4C which is what one might expect. So it would seem that the flow& return circuit absorbs more than 1/2 the pump head and the rad/rads, the other 1/2, this is actually the basis on which pump manufacturers determine the PP pump curves.

 

[Marck C]

Okay well... Now I have a new dilemma. Things have been working fine until the system developed a water leak on a faulty air release valve near the boiler. British Gas came out a couple of weeks back and fitted a replacement valve, but I've recently noticed now that the pump does not run at the same power rating anymore..🥴

Whereas setting III produced 45W it now produces only 33W
Setting II ran at 19W but now it only runs at 13W

The rads all still heat up hot to touch, but the system seems noisy by comparison to before. The 13W on setting II is ok, but anything more is too noisy to leave it at... ie I can get it to run at 22W if I set it to CP2 but the low hum is too noticeable.

Is 13W an ok power level?

What could be causing it to suddenly run at lower power levels?

Air in the system?

or summat else?

I'll probs ring BG on monday to see what they think, but it would be good to have some idea of what might be come up.

 

[John.g]

Only have my ancient Iphone3? to look at pump curves but all those (new) numbers tells me that the pump is practically circulating nothing on any of the settings so it looks like you have a air problem as its very unlikely that its a pump problem, I would suggest checking boiler pressure, boiler flow & return valves fully open, also open that newly installed vent if externally accessible or anywhere else that you can vent the system manually, vent the pump as this may be the problem.

 

[Marck C]

Only have my ancient Iphone3? to look at pump curves but all those (new) numbers tells me that the pump is practically circulating nothing on any of the settings so it looks like you have a air problem as its very unlikely that its a pump problem, I would suggest checking boiler pressure, boiler flow & return valves fully open, also open that newly installed vent if externally accessible or anywhere else that you can vent the system manually, vent the pump as this may be the problem.

Thanks again for your help John.g, I've since found the pump is only about 3 yrs old from its date stamp... I'm gonna ring British Gas again and ask them to take another look. I've tried all the rads and no air in any of them. The Alpha 2 doesn't seem to have a manual bleeding option so i'm a bit stumped on that. the only vent I can see is the new one and that one has nothing coming out either. I'll post back when I get a solution.. 😶

 

[John.g]

Its strange because on the three selected modes/speeds the pump seems to be producing the exact head for each, 3M, 4.5M and 6M, but at zero flow, it would point to something being shut off but don't know how you are getting any circulation at all, also the boiler should be cycling rapidly if no/low circulation, if you just briefly close the pump discharge valve and if the power (W) doesn't change then that means no pumping. I think that pump is pumping downwards? which doesn't help any air removal, not helped of course by not having a proper pump manual venting screw, if you have a unvented system you might consider pressurising the system to say 2.5 bar which might collapse some of the air bubbles (if present) and then reducing the pressure (if you can establish pumping) to its normal 1.5 bar or whatever by means of a rad vent.

You could also consider opening the ABV valve located just below the pump fully which might establish pumping, but carefully note its indexed setting before doing so and return it to this setting later.

 

[Marck C]

Very interesting....

Its an open vented system.. so i guess i can't pressurise it.

What i have noticed is that when the boiler cuts off the rate drops from 33w to 30w (Setting III) so its reacting to that.. does that indicate a level of flow

 

[John.g]

Possibly, I suppose, but would only be a few LPM at most, I wouldn't run the pump on speed iii with a open vented system, suggest CP1 or CP2, presume header tank is full of water, have you tried opening the ABV? Also assume you have run both CH & HW together, is the boiler running continuously once there is a demand?.

 

[Marck C]

Ok so we had a frost last night so pretty cold this morning when i turned to system back on to monitor... took about 30 minutes before all the rads started to get warm and 50 mins before they were all hot to touch. I'm guessing it should be quicker than that..

Header has water, cant seem to shift the ABV (and don't want to force it) and yes have had both CH & HW running at the same time and the pump continues to run at 13W on Setting II (I'm using Setting II for continuity as that's what its been on and runs quietest on)

Yes the boiler seems to run continuously (barring one hickup when it first started up from cold).

No pressure gauges to check pressure

I've been studying the pipework to understand the how the flow works... The flow out of the boiler is as you'd expect very hot... the return to the boiler is just warm (I can keep my hand on it)

All of this seems (logically) to suggest the flow is low... Its so perplexing.

I have British Gas coming out tomorrow as a follow up on the previous job, I'll leave the system cold for them so they'll get to see how it starts and performs from cold.

Will feed back after the visit.

Thanks again for you help... much appreciated as always 👍

 

[John.g]

50 minutes wouldn't be indicative of a very poor circulation rate IMO, but certainly is reduced based on the boiler return temperature, but how this is achieved with that indicated 13W on speed ii is a mystery to me, last April/May you were getting 19W which made perfect sense as it's ~ 10.2 LPM at a 3M head., 13W indicates zero flow.

You might consider just doing one more test (takes only 10/15secs) just shut the pump discharge valve and see what the indicated pump power is, then fully re open it, as you are at it just confirm that the pump suction valve is also fully open.

Just thinking about the circ flow again, assuming your boiler modulates to say 5kw then you may be circulating as low as 2 to 3 LPM which probably wouldn't be measured by the pump power......so either air or a blockage (severe).

 

[Marck C]

Ok tried shutting and opening the discharge valve... no change to the 13W.. The other inlet side is fully open.

 

[John.g]

OK, thanks, sincerely hope not but if BG drained down the system to install that air vent and if dirty then there is a chance that the boiler Hx is blocked.

 

[Marck C]

😳 That doesn't sound good...

They didn't need to drain it down as the boiler is upstairs and the valve is at the highest point.

From a logic point of view its been running fine up and till the leak... so seems to have been an issue since the air bleed valve was leaking... now that i've worked out how the flow runs I see the valve sits on the return right above the inlet to the boiler...

could air be trapped in the boiler?

Do boilers have internal bleed valves that BG might try?

 

[John.g]

There should definitely be one inside the boiler casing on the boiler flow, I think these are normally closed after initial fill or refilling so BG can certainly check this out.
Even though the boiler is upstairs the header tank must be still higher so they must have shut a isolating valve (if fitted) on the cold feed to remove the air vent?

 

[Marck C]

Great will prompt em to check it...Yep there is an isolating valve to the header tank ... which is open

 

[Marck C]

Solved! BG came and the engineer removed the pump... turns out the impeller was sludged up with a coating of crud. She cleaned it off reinstalled and it now runs sweet and like a dream... Full speed on all settings without any of the noise that I had before.

The whole system seems to be running so much better...

Go figure...

Thanks for you help John.g
I learn something each time in on here and am always grateful for the comments.. 🥇👏

 

[John.g]

Solved! BG came and the engineer removed the pump... turns out the impeller was sludged up with a coating of crud. She cleaned it off reinstalled and it now runs sweet and like a dream... Full speed on all settings without any of the noise that I had before.

The whole system seems to be running so much better...

Go figure...

Thanks for you help John.g
I learn something each time in on here and am always grateful for the comments.. 🥇👏

Greatt news alright Marck, wouldn't have thought that was the problem, we can all learn from that. What setting and power output are you on now?

 

[Marck C]

So it was left running on III at 45W but I'm probably gonna try running it on CP2 (35W) Looking at your previous power/flow rates CP2 seems a good balance..

It runs quiet as a mouse on all settings now..

 

[John.g]

Can you try it on CP1 which was your last permanent setting and see if the power is 20W as originally, it will also tell us exactly the head and flowrate now.

 

[Marck C]

just nipped up and checked it..... It is 20W on CP1

 

[John.g]

That,s 10.5 LPM @ 3m which is 12.9 LPM @ 4.5m (35W), all adds up.
Even though it doesn't matter now I wonder was the pump just air locked as that problem appeared almost overnight, its a great pity that they don,t have a real vent screw like before.

 

[doitmyself]

I see that there is an ABV immediately after the pump, presumably because there are. separate zone valves for CH and HW. (A mid-position valve does not normally require an ABV as at least one path is always open.)

However, an ABV is incompatible with PP, CP and Autoadapt modes. You can only use a fixed speed. The correct setting for the ABV will depend on the chosen pump speed.

 

[John.g]

I would agree but I don't know of any true fixed speed, constant curve A rated pumps now ( the DAB Evosta 4-7M did/does appear to have them), if you take the above pump, constant curve 3 gives a constant head of 6M between 0 and 12 LPM (0.7 m3/hr) & constant curve 2, a constant head of 3m between 0 and 10 LPM (0.6 ms/hr), maybe a ABV can be set up, in practice, but how?.

 

[doitmyself]

I assume that "the above pump" refers to the OP's Alpha 2, not the DAB Evosta.

I would also assume that, if the pump needs to be set on fixed speed III and the flow is less than approx 0.2 l/s, there is something wrong. The most obvious being that the system is not correctly balanced.

However, my reason for pointing out the problem of using an ABV on anything but a fixed speed, is that it will completely mess up the flow through the system. In PP mode the ABV will open more when the flow rate increases, and vice versa; which is the opposite of what is required. In CP mode the ABV will be either permanently open or permanently closed. depending on the setting of the ABV and the chosen CP setting. As for Autoadapt, who knows what will happen!

The setting of an ABV when a modulating boiler is involved is completely different from that when a fixed output boiler is concerned.. With a fixed output boiler the flow rate through the boiler needs to be constant as the boiler output is fixed. So any reduction in flow rate, due to TRVs, MVs etc closing has to be corrected by the ABV opening. If a modulating boiler is used, any reduction in flow rate will result in an increase in flow temperature. So the boiler will modulate down to maintain the set temperature. It isn't until the boiler is running at minimum output that an ABV is necessary.

 

[John.g]

Again, I would agree with you completely but these pumps including the Alpha 2 do not provide true constant curves modes, constant curve ii at 3M has a constant head of 3M between 0 and 10 LPM, it is only when the flow rate exceeds 10 LPM that the head starts falling, in true constant curve fashion, so just as difficult IMO to set up as on constant pressure mode.
If a pump like the Dab Evosta 4-7M (a A rated pump) was installed and set to constant curve 1 at 4.2M then the head will fall to 3M for that required flow of 10 LPM and for example if a modulating gas boiler requires a minimum flow rate of 3 LPM @ 5 kw to maintain a boiler deltaT of 25C then the ABV can be set slightly lower than 3.8M, the ABV will then close once the flow rate increases above 3 LPM as the (dab) pump head will again start falling.

 

[Marck C]

Thanks 'Doitmyself' and 'John.g' for your continued comments on this topic -intriguing stuff if not a little beyond me.

I will try to comment as far as i'm able i nthe hope of filling some info gaps

1. RE ABV: it is after the pump and set at 0.3 (see pic) and there are indeed two separate valves (CH & HW) does that setting seem appropriate?
2. The BG engineer suggested it go onto setting III and as it ran quietly I thought ok fine. I did hear that setting III was to high for an open system. I'm happy to be guided on this...
3. By 'messing up flow' I'm guessing that means that the higher system pressure from setting III would 'trick' the system into diverting the heated water as it would if all the TRVs are closed. meaning that the rads wont get the heated water circulation when they are actually open and calling for it.. would that mean that the rads would not get hot? I can tell you that all the rads currently get hot.
4. RE Modulating boiler V fixed output so mine is an Alpha 18CDR is that modulating? The boiler has a manual dial type thermostat on it 1-9... I have it set at about 6.25

My other thoughts

1. The sludge on the pump rang a few alarms bells. Its an old system of pipes n rads which I'm guessing is going to be holding some sludge and crud. There is a Fernox filter on it which has been cleaned out twice since weve been here and both times it had an amount of sludge and metallic crud on it tho water from the rads on bleeding runs clear n clean. This tells me at some point we need to consider NEW RADS and a POWER FLUSH. I may well get some quotes at some point. Just don't want to mess with that right now.. I'd prefer to wait until the spring when it ain't so cold and all seems to be functioning at the mo.
2. I know the pump was fitted within the last 3 years as its date stamped at 3 yrs old... Of course i've no idea how long it had been sat on someone's shelf before fitting. No idea if the ABV setting was considered by the fitter at that point, or even if that's relevant.

hope some this helps with your thoughts on it...

Having considered all this... What pump setting would you recommend? Is there a consensus between you?

 

[John.g]

I think your boiler does modulate, probably down to 5 or 6 kw but not 100% sure.

I think you were reasonably happy a few months ago with CP1@ 3M and are now running with CP2 @4.5M, I would say either of those, whichever gives you all rads heating equally etc, my system, similar to yours runs at a 3M head equivalent, in PP mode set to 4.3M. Your system should run quite well with a 3M head if its reasonably clean.

ABV setting: I would be very surprised if your heating engineer set the ABV to 0.3 on CC iii (6M) is this would result in a huge recirculation rate of ~ 14/16 LPM, greater than your system demand which would result in a much higher boiler return temp and reducing boiler efficiency, on CP2 setting (4.5M) you would still be recirculating ~ 11 LPM with the ABV set to 0.3, I would say, based on the pump power of 35W on CP2 that the ABV is full of crap and not recirculating anything as I would have expected a power demand of ~ 42W on CP2, IF the ABV is clear and you wish to remain on CP2(4.5M) then suggest setting the ABV to 0.43 which may give you a minimum flow rate of 3 or 4 LPM. If happy to run with CP1 (3M) then set the ABV to 0.28.
If running on CP2 (4.5M) just now then the outlet pipe from the ABV should be roasting at that setting of 0.3 so adjust as required for CP2 or CP1 as appropriate.
Practically, you probably should just set it slightly higher initially and then very very gradually keep reducing the index until you just feel the by pass outlet getting hot, ie on CP2 set to 0.50 and then gradually reduce, on CP! set to 0.35 and do ditto.

 

[Marck C]

I've a feeling the ABV hasn't been moved since it was installed and probs never touched when the new (probably more powerful ) pump was installed. It may well be crudded as I cant seem to adjust it. Presumably adjustment is by twisting/turning the plastic cover, but I can't shift it and again don't want to bust it. As there appears to be no way to isolate it cleaning it out doesnt seem an option

From what I remember wasn't Setting II giving me 3M? If I cant adjust the ABV wound it be best to stick to setting II?

 

[John.g]

These were the readings you got early last April and you finally settled on CP1 (3M), see your post #13, page2, but as CC setting ii gives almost the exact same outputs as CP1 for your required flowrates the head does eventually fall off so it might be the more appropriate mode if you do get the ABV cleaned up (or renewed) and operational.

III - 45W (6M)
II - 19W (3M)………….3.0M & 11.6 LPM
I - 6W (1M)
AuotpAdapt went up to 32W but quickly dropped to 12W
PP1 - 10 W (1M)
PP2 - 14 W (3M)……...2.0M & 10.3 LPM
CP1 - 20 W (3M)……..3.0M & 11.7 LPM
CP2 - 35 W (4.5M)....4.5M & 14.67 LPM

 

[Marck C]

Thanks... Will try and see how it performs for a day or so

 

[doitmyself]

What is the make of the ABV (if any info)? That would help locate the instructions.

Is the exit pipe (other side from the pump) of the ABV hot all the time, partiularly when the system first comes on?

Grundfos recommend setting the pump to a fixed speed (I, II, III) if an ABV is required.

I would suggest using fixed speed II. This gave a working point of about 0.6 m³/hr and a head of about 3m. The fixed speed curve is almost flat below that point, so the ABV will have to be adjusted carefully to ensure it only opens when the flow rate is below, say, 0.3 m³/hr. The Alpha CDR has temperature senssors for flow and return and will modulate the boiler accordingly to maintain the required flow temperature without exceeding a safe return (recommended differential = 20C).

 

[John.g]

Possibly this one (attached)

 

[Marck C]

Looks very much like that ABV john.g. but now there's another development. 🙄

The CO alarm went off in the boiler cupboard today. The alarm has an LCD which registered a reading of 46.

Boiler had just restarted by time I got to it, running quietly on setting II at 19W. Obviously I turned it all off opened the windows n Rang BG and they got the emergency Gas guy out who came out quick enough... but it seems it was a one of burst/blow back from somewhere, it was all clear by the time the guy came so its all off until BG can come and check it over again. 🤷‍♂️

 

[doitmyself]

Thanks. John.g.

I was hoping that there was a locking mechanism on the valve, which there is. The document says:

"Once set, the valve can be locked in position by tightening the screw in the cap."

So all the OP needs to do is locate and loosen the screw, and then he shoud be able to adjust the valve. If it's like most ABVs the adjustment will have a very low gearing, so you will need to turn the adjuster about ten turns to get the pointer to move one division.

 

[John.g]

That should free it up alright but if it was at 0.3 while running in either speed iii (6M) or CP2 (4.5M) then there would or should have been more recirculating than the system demand using a Honeywell DU144 setting chart as a guide, the Biworld only gives a flow rate chart which I don't understand even though I do know what a valve Kvs is.

 

[doitmyself]

The boiler has a minimum output of 5.4 kW so the flow rate at 20C differential is 5.4/(4.18 x 20) = 0.646 litres/sec. This is shown as the red box on the pump chart below. (The normal working point is the green box.). The head, at the normal point is just below 3m, but it's just over 3m at minimum output.

Now plot the flow and pump pressure at minimum output on the ABV chart as in this pic (I have assumed that 1m =0.1 bar):

This gives a point just below the 0.3 line. Moving twards the Y axis, parallel to the 0.3 line we cross the axis at about 0.29. So the ABV has to be set to 2.9. It's then a case of fine-tuning the ABV so it only opens when required, e.g when both motorized valves close.

 

[Marck C]

🤔 Thanks again guys... BG have been ..no fault found after a good check up.... all rads hot and were back onto having a warm house again.... as the ABV is on 3 and setting II runs at 3 i'm gonna leave well alone. Here's hoping 😎