Grundfos Alpha 2 15-60 130 Setting?

[woodpeckerx]

I wouldn't go so far as to say they are no good but have seen very poor posts re their TRVs, if you have replaced it again with another Tower and it works, then fine.

The ABV seems to have started working again, I ran the pump on c3 for a while and did a couple of air purge cycles which seemed to help, maybe had air in the system. The valve now has to be set quite low to open which also doesn't seem quite right though.

Are the readings above taken with all 15 rads "on" with the TRV heads removed?.

Yes all rads with TRV heads off, Drayton valves were set at the index I calclated for a dT of 12 when I measured. I will probably reset them back to dT20 and see whether things have improved with the new pump. I've opened the valves up at the moment to let the F3 get around everything with less restriction.

Now need to determine the best setting, PP with a 3.5m head seemed to work well and once the ABV sorted itself that seemed to be working as well, on the overun when the CH valve closed I could tweak the ABV to really trim the flow through it but not sure if PP mode will play well with the ABV, more experimenting required.

The pump seems fantastic, the 0.1m increment adjustments and flow indication are great.

 

[Johntheo5]

The ABV seems to have started working again, I ran the pump on c3 for a while and did a couple of air purge cycles which seemed to help, maybe had air in the system. The valve now has to be set quite low to open which also doesn't seem quite right though.


Yes all rads with TRV heads off, Drayton valves were set at the index I calclated for a dT of 12 when I measured. I will probably reset them back to dT20 and see whether things have improved with the new pump. I've opened the valves up at the moment to let the F3 get around everything with less restriction.

Now need to determine the best setting, PP with a 3.5m head seemed to work well and once the ABV sorted itself that seemed to be working as well, on the overun when the CH valve closed I could tweak the ABV to really trim the flow through it but not sure if PP mode will play well with the ABV, more experimenting required.

The pump seems fantastic, the 0.1m increment adjustments and flow indication are great.

I'd throw out that ABV and install a Honeywell DU144. OR
if you only require the ABV to open on pump overrun when the boiler and zone valves shut, just install a normally open 2 port valve powered from the same WC terminal where the zone valve orange wires are, when any one of the zone valves open then the 2 port normally open valve will close but not reopen until all zone valves start closing (deenergised)

Its very difficult to set up a ABV with modern A rated pumps because even the CC, fixed speed punp curves are more like CP curves right at the spot where you need the ABV to open, the Wilo isn't the worst, see below, Its almost impossible to set up a ABV with CP mode, PP mode is out because you will need a 4M setting to give a actual pump head of 3M from looking at your flow readings, this means that the ABV woul have to be set to ~ 1.8M to give say 300LPH with a pump head of 2.0M (with zone valves closed) but the ABV will then give a enormous flow at a 3M head. You are far better off IMO to install either a manual valve, once set up at 2M and assuming you use PP4, then the flow rate will "only" increasy by 22% at a 3M pump head, if you opt for CP mode then the by pass will be essential constant. You could install the new ABV with a manual valve and play around with both, you can install a Tachosetter with (or without) the ABV which is a manual valve but shows the flowrate.

 

[woodpeckerx]

you can install a Tachosetter with (or without) the ABV

I was looking at those earlier and thinking about that in series with the ABV. Would that work with PP mode on the pump?

 

[Johntheo5]

Yes, it will, the tacho (since its "manual" ) will only allow the flow rate to increase by a maximum of ~ 22% no matter how much the ABV opens, the downside is that there is allways a bypass, required or not, if, say the boiler return flow/temp is 12LPM/50C and the minimum required bypass is 5LPM, with a boiler flow temp at 70C, the return temp will rise from 50C to 55.9C, the bypass flow will increase to 6.1LPM at 3M resulting in a return temp of 56.7C, no big deal if the boiler is not in condensing mode, will result in a efficiency loss of well less than 0.5% but will have a greater effect if the boiler is in condensing mode, with boiler flow/return temps of 60C/40C, the bypass(s) will result in returns of 45.8C and 46.7C with efficiency loss of ~ 2 to 2.5%.

 

[Johntheo5]

You have the perfect flowmeter already, your Wilo flow readings, why not just install a gate valve with the ABV, you must/should then set it up only when the zone valves are shut, can probably do it while the boiler is cycling off as the circ pump will be running, but maybe best to remove the pump cable and stick a plug on the end and plug it into a extension lead. (Boiler OFF). You can then set the initial flow rate up by setting the ABV with the gate valve wide open, maybe set the ABV to give a flowrate of 0.5m3/hr (8.3LPM) and then throttle the gate valve to give you the minimum flow required, say 0.2/0.3m3/hr, 3.3/5.0LPM, you can then open your CH zone valve or/and the HW zone valve(s) manually and note the increase in flow rate when the pump ramps up?. Doing it this gives you plenty of time to experiment as you dont have to wait for the boiler to cycle off. It would also be interesting to see the increase in flow just using the ABV with the gate valve wide open, when you open the zone valve(s).

 

[woodpeckerx]

You can then set the initial flow rate up by setting the ABV with the gate valve wide open

I'm leaning more towards a tacosetter inline with the ABV, would that give more accurate flow control?

Is the Honeywell ABV much better than the Tower I have? If so I'll replace that as well.

Having watched the boiler I think I could also shave 5 degrees off the flow as its hitting 70 degrees at the moment. I realise the need to try and keep the return temp low and below the ~54 degree exhaust dew point to keep it condensing mode, this was part of the reason for using these Drayton valves as they *seemed* an easy way to maintain the dT20 balance across the rads as TRVs in the system open and closed.

It seems this system was fitted with an A rated condensing boiler but the flow was originally left at 80 degrees, rads were fit the metal recyling yard, the ancient Drayton TRV2 stats were mainly jammed in the fully open position and I doubt anything had ever been balanced at all.

 

[Johntheo5]

The tacho is just another throttling device but has a flowmeter which you don't require, I don't see any reason why a gate valve will not do the same job but the choice is yours.
The Honeywell DU144 is a excellent ABV, I've installed a few for friends and they work exactly as they should.

 

[woodpeckerx]

The tacho is just another throttling device but has a flowmeter which you don't require

I see, I thought it had some fancy flow restrictor, its really just a valve with a measuremnt scale on it then.

 

[Johntheo5]

Not really, the flow setting is done with a screwdriver slotted ball valve, I oten wonder as well what advantage, if any is achieved with the installation of the ABV + the throttling device, it will be very interesting to see your test results when you try (hopefully) different settings, ie ABV set to minimum (max flow) with the throttling valve set to the required and then opening the zone valve(s) and the ABV doing all the work with the throttling valve wide open, and with the ABV set to say 0.5m3/hr and the throttling valve then set to reduce the flow to 0.2/0.3m3/hr.

 

[Johntheo5]

This is from someone with 10 rads and a (healthy) Grundfos Alpha 2 and gives some idea of what its performance is., it should be practically identical to the Wilo at the same heads. Wilo: C1=2M, C2=3.8M & C3=6M. Grundfos Auto Adapt very poor.