Grundfos Alpha 2 AutoAdapt is slow

[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 😎