Welcome to the forum. Although you can post in any forum, the USA forum is here in case of local regs or laws
Be alright if they'd open at all. Forum glitch?
I'm also doubting my own comment about a 3m head at 6l/m on speed 1. I've found a UPS 15-50 manual online, but it isn't the correct one as not 40/70/105W. I'm also doubting that my version was the correct version.
Quite why Grundfos has to give the same model number to so many versions of the pump is a bit beyond me!
Well, I suppose if the system is designed correctly, issues such as pumping over should not happen, even if the new pump head is wrong.
What you'd realise if you were in the trade is, however:
A. The old pump setting was probably already wrong. People fiddle with things even if the original installer left the setting correct.
B. Systems often aren't designed properly.
C. Quite possibly the system was never properly balanced by the original installer.
However, agree that it is very good practice to note the previous setting before changing the pump. It gives you a starting point at least!
I noticed the difference between the pic of the 15/50 and the pump curves, both posted by the OP. The wattages may be different but the amps are the same. Then I noticed that the curves say 230V but the pump says 240V, which would account for the higher wattages on the pump. So I reckon the curves do refer to the pump in the pic..
I think it was around the end of the '90s when the UK and Europe decided to 'harmonise' the mains voltages - one used 220V and the other 240V. A change to 230V for everyone and a change of tolerances and, hey presto, the UK manufactured goods met the European Standard, and the European manufactured good met the UK standard. In reality, nothing had changed.
I think a lot of problems with pump change out in vented systems is that one might think that just selecting CC2 would be a reasonable setting but even if both heads are exactly the same, the A rated pump curve is in fact constant pressure for most system requirements, the only constant curves (of a sort) are the PP ones. If someone has a direct line to Grundfos (or any manufacturer) they might ask the reasons for this, the only pump I have seen with apparent real constant curves was/is the DAB Evosta 4-7.
Can I just add that in a properly designed and executed system you should never have pumping over. If the V,C,P are plumbed in correctly and the pump is sized correctly then the pump head will have pretty much diminished by the time its circulated around the system, back through the boiler and towards the pump again.
Of course as mentioned above not every system is designed or executed properly.
Of course as mentioned above not every system is designed or executed properly.
The most important difference to note between PP and the old-style constant speed is that a PP mode will INCREASE the head as the flow rate increases (to compensate for increased pressure losses in the primary flow and return) whereas a constant speed pump will demonstate a DECREASE in head as the flow rate increases. This is generally designed for a radiator system with TRVs. So, as you say, there is a curve on PP, but it is the inverse of the pump curve of an old-fashioned pump.
I do see your point. The flat section of the constant-speed 'curves' means that for a differential-pressure ABV to function, the latter has to be set to open well to the right of the flat section, with the result that it will be open for all but very high flow rates.
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Are you sure about this? I'm thinking that since those old pumps were controlled by the electrical resistance of the windings, if the pump were rated at 230V and that same pump were then supplied with 240V, the current at the 230V rating would be lower as it is the the voltage that is driving the current and the resistance/impedence would be much the same. Ready to be taught that I'm wrong though...
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What about the apparent > unity Power Power Factors, they are all at or greater than 1, (selectric, post #21),maybe the capacitor achieves this, my semi retired ancient Salmson labels 65W @ 230V&0.28A, equals PF of 1.009.
John my understanding is and bare in mind I am not an electrician, im only studying it in my spare time, that the power factor will never exceed unity or 1.
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
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
Attachments
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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.
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.
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.
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.
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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.
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.
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.
J
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!
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