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Variable speed pump question.

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Steve57

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Hi. I have a sealed heating system, Vaillant Ecotec Plus 418 boiler, 10 rads, TRV's on all bar the one in the living room where the thermostat is. I have an automatic bypass and an unvented hot water cylinder. The circulating pump is a Grundfos UPS2 15-50/60. The system seems fine on any speed but what is this variable speed setting I’m reading about? I believe it can be activated by holding the speed selector button depressed for a few seconds. Is that right, is it worth doing or shall I just leave it on speed two?
Thanks
 
Push button until it flashes set to number 1 (flashing) see how it goes with the heating only on if not all the rads get hot set to speed 2 (flashing). Saves electric & cuts down on system noise etc.
Time the hot water to come on before the heating especially in the morning.
If you had a 6 or 8 series Vaillant it would now come fitted with a variable speed pump so why would you not select it on your external one???
 
Steve57 said:
I don’t doubt your advice but what is the point of them? Do they work automatically by adjusting the speed dependant on how many TRV's are open?
Click to expand...
They do, the highest setting that you can set the UPS2 PP (proportional pressure) setting is setting 3 which ranges from 3.0 M to 1.2 M and will automatically change this head depending on the number of rads in service and/or TRVs position.
Before changing to PP setting 3 I would first change your fixed speed setting from 2 to 1 which corresponds to a 4M pump, (speed 2 = 5M pump) and if you are happy that all the rads are heating OK then go to PP setting 3 and see how you get on. I have my pump (Wilo) on a PP setting of 4 M, I found that the 3 M setting (which is the max available on a UPS2) was too low for my needs, I have a similar set up to yours, 10 rads, (8 on TRVs, 2 on thermostat).
 
I had a UPS2 fitted about a year ago and it's running fine on fixed speed 1. I have been thinking of setting it to a variable speed but am reluctant to do this as I can't work out what the effect will be. One problem is that there is very little difference between the three speeds. This chart shows the current working point, obtained from data provided by my Remeha Avanta 18V boiler - downrated to 15kW.
The pump is producing a head of 3m with a flow of 0.8m³/hr (equivalent to 15kW with a 16C differential).

UPS2.PNG

What I would like to know is: what will be the operating point if I select one of the variable speeds? If the flow rate increases, that's no problem as the rads will produce more heat. But if the flow rate decreases could the flow/return differential exceed the recommended maximum 20C (o.65m³/hr)?
 
doitmyself said:
I had a UPS2 fitted about a year ago and it's running fine on fixed speed 1. I have been thinking of setting it to a variable speed but am reluctant to do this as I can't work out what the effect will be. One problem is that there is very little difference between the three speeds. This chart shows the current working point, obtained from data provided by my Remeha Avanta 18V boiler - downrated to 15kW.
The pump is producing a head of 3m with a flow of 0.8m³/hr (equivalent to 15kW with a 16C differential).

I reckon that based on your above info that you would now have a flow rate of 10.05 LPM (0.6 M3/hr) @ 1.7 M head and a boiler deltaT of 21.4C.
Unfortunately I cannot upload the S.sheet (my own) to show the method that I used to arrive at the above but its pretty accurate based on my own findings.

I agree that the UPS PP speeds are far too close, they should certainly have a PP setting of 4 & 5 IMO.



View attachment 36243
What I would like to know is: what will be the operating point if I select one of the variable speeds? If the flow rate increases, that's no problem as the rads will produce more heat. But if the flow rate decreases could the flow/return differential exceed the recommended maximum 20C (o.65m³/hr)?
Click to expand...
 
doitmyself said:
I had a UPS2 fitted about a year ago and it's running fine on fixed speed 1. I have been thinking of setting it to a variable speed but am reluctant to do this as I can't work out what the effect will be. One problem is that there is very little difference between the three speeds. This chart shows the current working point, obtained from data provided by my Remeha Avanta 18V boiler - downrated to 15kW.
The pump is producing a head of 3m with a flow of 0.8m³/hr (equivalent to 15kW with a 16C differential).

View attachment 36243
What I would like to know is: what will be the operating point if I select one of the variable speeds? If the flow rate increases, that's no problem as the rads will produce more heat. But if the flow rate decreases could the flow/return differential exceed the recommended maximum 20C (o.65m³/hr)?
Click to expand...

(might have posted this before)
I reckon that based on your above info that you would now have a flow rate of 10.05 LPM (0.6 M3/hr) @ 1.7 M head and a boiler deltaT of 21.4C.
Unfortunately I cannot upload the S.sheet (my own) to show the method that I used to arrive at the above but its pretty accurate based on my own findings.

I agree that the UPS PP speeds are far too close, they should certainly have a PP setting of 4 & 5 IMO.
 
John.g said:
(might have posted this before)
I reckon that based on your above info that you would now have a flow rate of 10.05 LPM (0.6 M3/hr) @ 1.7 M head and a boiler deltaT of 21.4C.
Unfortunately I cannot upload the S.sheet (my own) to show the method that I used to arrive at the above but its pretty accurate based on my own findings.

I agree that the UPS PP speeds are far too close, they should certainly have a PP setting of 4 & 5 IMO.
Click to expand...
Should have said the above flow rate/head should apply if the highest PP (3M) setting is selected
 

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