Grundfos UPS3 Pump Modes

[John.g]

You are quite correct SJB since the cosine of 0 deg is 1, I was just showing the calcs based on the face plate label, I don't seem to be able to get into the electrical forum to post a query re the apparently very high PFs of the old type traditional circ pump motors. I thought originally that the starting capacitor was "left" in the circuit but was able to disprove this on a old Salmson unit, not the above one.
For example, take my own Wilo ST circ pump (~ 11 years old) powering my solar system, the PFs for the 3 speeds, starting at the lowest are, by my calculations, respectively, 0.93, 0.88 & 0.99. My A rated Wilo Yonos Pico CH circ pump motor gives a measured 0.53 which IMO is more to be expected but all the pump manufacturers were hardly posting incorrect numbers.
Some electrical people who are reading this might care to comment or I can repost it in the electrical forum if someone points me in the right direction

The attachment is a bit hazy so the numbers are, 230V/0.20A/43W, 230V/0.3A/61W & 230V/0.36A/82W

 

[decomplexity]

Indeed. Differential-pressure ABVs will simply not work as intended in systems using domestic pumps with PP or CP. As Ric2013 notes, when using PP, the LH end of the ‘head vs flow’ curve is ‘low head - low flow’, as would be the case in warm weather when the TRVs are mostly closed or throttled down. However, this is just when the ABV should be opening to maintain the minimum flow to the boiler, but since the head is low it is exactly when it WON’T open. With CP, the head of most domestic pumps is virtually flat from no-flow to a high flow where it slowly tails off. Again, we would want the ABV to open for no-flow or low-flow, but if the ABV is set to open at the no-flow head, it will be open constantly except at peak flow.

And anyone who keeps one radiator permanently ‘open’ (i.e. without a TRV) may be misleading themselves that this is sufficient; it will only be so if the radiator is in the bypass circuit (i.e. in neither the DHW or the CH circuits) as towel rails sometimes are. Otherwise, when both DHW and CH motorised valves are shut, the boiler will have no cooling flow at all on pump overrun (assuming it needs overrun).

Instead of a differential-pressure ABV, what is needed is a constant flow bypass valve that is set to pass the minimum flow rate of the boiler. I use a Caleffi 127 Autoflow compact automatic flow rate regulator (usual disclaimers) that worked out cheaper than a differential-pressure ABV. One could add to the boiler infeed a flow rate sensor that opens a motorized bypass valve when the flow rate drops below the boiler minimum, or replumb to use a low-loss header (or closely-coupled tees), but the constant flow bypass valve is the simplest and cheapest solution.

 

[John.g]

I have spoken to Wilo UK technical re the above constant curve/fixed speed being in fact constant pressure in large part and the guy there seemed to be saying that the fixed speed is kept precisely at its SP (no motor slip) in CC mode leading in part to this flat "curve" characteristic, but of course since these are smart pumps there surely is no reason whatsoever why it can't replicate a true constant curve which works/worked extremely well with a differential pressure ABV which will then give no flow under normal conditions, the required minimum boiler flow rate and a very high flow rate on boiler shutdown/pump overrun. The Caleffi 127 Autoflow certainly meets most needs in any pump mode apart from the high flow rate which may be (rarely) required under certain conditions, so a excellent choice .

I think the Grundfos Alpha 3 Model B displays RPM, head, flow, power, it would be very interesting if some reader had one of these and ran it in CC mode and then see what effect a change in flow rate has on its head, speed and power.

 

[Ric2013]

I use a Caleffi 127 Autoflow compact automatic flow rate regulator (usual disclaimers) that worked out cheaper than a differential-pressure ABV.

I'm struggling slightly to get data on precisely what these are. I take it you buy one that is preset to the flow rate required and that this device then maintains that flow rate even though the differential pressure may increase or decrease.

Would this be an issue with regard to Part L in that you now have a pump delivering the minimum flow rate through the bypass even when there is adequate flow through the system thus slightly increasing the load on the pump, and (excuse my ignorance) is it a problem that the boiler is now receiving flow temperature water straight back into the return, perhaps reducing its ability to condense?

Silly questions, I know, but my understanding is a boiler may require a minimum flow (and, on older boilers) a minimum heat loss on that flow, but in light of smart pumps I'm slightly at a loss at how this is to be correctly achieved.

 

[John.g]

Yes, that's basically it, have a read of this.
Constant flow automatic bypass valves | Page 3 | PlumbersForums.net

Re your query on condensing effect, it can/will have a effect but this is dependent on the boiler return temp as condensing doesn't begin until ~ 55C. Using a few numbers, if your boiler requires 4 LPM minimum flow and assuming a boiler temp of 70C with a return of 50C and a flow rate of 10 LPM with no by pass, because of the constant by pass you will have 10 LPM at 50C mixing with 4 LPM at 70C resulting in boiler return of 55.7C so a loss in condensing effect, if the flow through the rads was only say 4 LPM (if TRVs fitted) then the return may only be 45C but mixed with the 4 LPM bypass at 70C will result in a boiler return of 57.5C, not hugely different in temperature but a fairly significant difference in condensing effect.

You can see the effect of the different return temperatures here on boiler efficiency.

 

[Johngt40]

Excuse me for jumping in on this thread but just fitted a Grundfoss UPS3 pump time my central heating and in PP 1 or 2 when running the less continually flash, is this correct!

 

[John.g]

As below, the yellow or yellows flash, I think, depending on which mode is selected. Would suggest PP2 as PP1 is very weak at 1M to 2M, PP2 gives 1.9M to 3.8M.