Which is the more powerful pump?

[rcpilot]

Hi all just picking your brains 2 pumps with flow rates of 3.8 and 5.7 which is the more powerful, also can you fit a commercial pump into a domestic system?

 

[ShaunCorbs]

5.7 is a higher flow rate but might be the same pressure as the 3.8

Need more info

 

[rcpilot]

what info would you need ?

 

[ShaunCorbs]

Are we taking heating or water and what’s the problem with the existing set up ?

 

[rcpilot]

Hi all well here is the problem in it's entirety, when we bought our house ( 2 bedroom ) up and down, the central heating was by way of a back boiler it had 3 radiators upstairs and 3 downstairs, but because of concrete floors downstairs, as it was previously council owned, the downstairs radiators were on what is known as dead legs. I put in a feature fireplace and ( as then you did not have to be gas safe ) I put a wall hung boiler in the bathroom and installed a fully pumped15mm pipe "Y" plan system which was open vented. The pump was a bog standard Grundfos one and as the boiler was getting long in the tooth I decided to get it replaced, in doing so I noticed that there was something wrong with the pump ie the body could be scraped with a knife and large chunks could be cut out of it so that was replaced with a new one. the chap who replaced the boiler put in a pressurised system. Not long afterwards I decided to take out the radiator in the bathroom and install a heated towel rail, now this was a big one, I noticed that the radiator in the entrance way was not getting hot at all but just left it . After a while I decided to get a Grundfos Alpha 2 L pump but it made no difference, so I then decided to get a Grundfos alpha 3b and take out the radiator in the sitting room and put in a big 2 panel one , for got to mention that I replaced all of the rads in the house with modern single panel ones the full length of the windows and put the bedroom ones on TRV's,. this is where everything went wrong, the Alpha 3b is setup and balanced using the 2 apps, Go Remote and Go Balance but these would not touch my system and could not balance it no matter what I did, I tried my best to manually balance the system, as I know how to, but that made no difference either, the entrance rad would not heat up the big one in the sitting room would not heat up the kitchen one would just get warm to the touch (these are all the rads on the dead legs) upstairs ones were getting quite warm, now I am left with the upstairs heating ok but nothing downstairs ( there are no air locks) I have come to the conclusion that the Alpha 3b is not powerful enough to pump the water round the system, I have spent quite a bit of time and money on pumps to try and rectify this problem but to no avail, so if any one out there knows of a powerful pump that can do the job drop me a line, one other thing I have come across is a Super 25 pump but it is a commercial one is there any reason why I cannot install it in my system obviously I would have to extend the port dimension as it is 180 mm not 130.

 

[ShaunCorbs]

a standard 15-60 eg ups2 or ups3 will be more than good enough for your system but it sounds like you have either a design issue or a blockage changing the pump
Won’t change much

 

[John.g]

The Alpha3 may display the head in meters, the flowrate in M3/hr and the power in watts, does it?.
What control mode are you running it on, CC (constant curve), CP (constant pressure) or PP (proportional pressure) ?.

 

[rcpilot]

a standard 15-60 eg ups2 or ups3 will be more than good enough for your system but it sounds like you have either a design issue or a blockage changing the pump
Won’t change much

Problem is it is the same design as before the only thing I have done is replaced the bathroom rad with a heated towel rail and replaced the flatpanel rad in the sitting room with a big double panel one, i know for certain that there is no blockage in the system because when I did the work I used the rad valves to get water down the dead legs on both sides of the rads before I connected then up.

 

[rcpilot]

The Alpha3 may display the head in meters, the flowrate in M3/hr and the power in watts, does it?.
What control mode are you running it on, CC (constant curve), CP (constant pressure) or PP (proportional pressure) ?.

yep head in meters and the flowrate in M3/hr and power in watts and it is on proportional pressure

 

[ShaunCorbs]

It’s not a pump problem as it’s very unlikely you have two bad pumps out the gate

You sure it’s not a one pipe system?

 

[John.g]

yep head in meters and the flowrate in M3/hr and power in watts and it is on proportional pressure

Give us the numbers then please , and the PP setting, should be a good indication of whats happening.

 

[John.g]

Hope its not on Auto Adapt, if running at ~ 9W then will pump nothing.

 

[rcpilot]

It’s not a pump problem as it’s very unlikely you have two bad pumps out the gate

You sure it’s not a one pipe system?

I'am not saying the pumps are bad, I am saying they are not powerful enough to pump the water round the system because of the dead legs, I am going to do an experiment tomorrow and will let you know the outcome

 

[ShaunCorbs]

Unless the dead legs are connected together which your system would never work these dead legs don’t matter as there just capped off services

 

[John.g]

I'am not saying the pumps are bad, I am saying they are not powerful enough to pump the water round the system because of the dead legs, I am going to do an experiment tomorrow and will let you know the outcome

Can you get any readings from the pump as it will reveal quite a lot IMO.

 

[Ben-gee]

Shaun OP is saying dead legs when what he actually means is drops.
This is a case of a little knowledge is a bad thing!

 

[ShaunCorbs]

Shaun OP is saying dead legs when what he actually means is drops.
This is a case of a little knowledge is a bad thing!

Agreed kinda guessed that also probably old back boiler with I’m guessing when removed flow and return linked hence why no flow to the rads as it’s talking the easiest route

 

[rcpilot]

Give us the numbers then please , and the PP setting, should be a good indication of whats happening.

Hi all well what I did was shut off all the upstairs rads so just the downstairs rad were open, set the pump to constant curve @100% operating mode @Max estimated head was 5.9 m and the speed was 5295.
The sitting room rad (which is the new big one) got hot but I could not balance it, the kitchen one which was cold or just barely warm was heating up but did not get hot, the entrance rad was still cold, my conclustion is either the pump cannot push the water round the system (all the above rads are on dead legs) or there is a blockage or trapped air in the return legs, which all I can do is bleed the return legs (not the rads) and see if it makes any difference, if it does not then the only solution is to find a much more powerful pump, if anyone can tell me what would happen if I fitted a commercial pump, of which I have the specs :- UP UPS 14m3/h 13m head pmax 10bar
UPS 25-80 :- 8.5m3/h 7mhead

 

[rcpilot]

Agreed kinda guessed that also probably old back boiler with I’m guessing when removed flow and return linked hence why no flow to the rads as it’s talking the easiest route

When I took out the back boiler I renewed the upstairs pipework to 15mm flow and return, the downstairs (as the boiler is upstairs) was put on dead legs or drops 15mm flow and return

 

[ShaunCorbs]

Do the test again but shut all but one rad eg one problem one does that get hot ?

 

[John.g]

Hi all well what I did was shut off all the upstairs rads so just the downstairs rad were open, set the pump to constant curve @100% operating mode @Max estimated head was 5.9 m and the speed was 5295.
The sitting room rad (which is the new big one) got hot but I could not balance it, the kitchen one which was cold or just barely warm was heating up but did not get hot, the entrance rad was still cold, my conclustion is either the pump cannot push the water round the system (all the above rads are on dead legs) or there is a blockage or trapped air in the return legs, which all I can do is bleed the return legs (not the rads) and see if it makes any difference, if it does not then the only solution is to find a much more powerful pump, if anyone can tell me what would happen if I fitted a commercial pump, of which I have the specs :- UP UPS 14m3/h 13m head pmax 10bar
UPS 25-80 :- 8.5m3/h 7mhead

You are pumping practically NIL as you can see from the pump curve that the flowrate at 5.9M is 0.
The pump power is 22/23kw, you should see this displayed and also the flowrate showing 0 M3/hr, so you might note these.
Also just shut the pump outlet valve for 10 secs or so with it running and the above numbers 5.9M/22kw/0.0M3/hr should remain the same.

 

[rcpilot]

Do the test again but shut all but one rad eg one problem one does that get hot ?

Hi well interesting results:- I turned off the rad in the sitting room (which is 2400mm x 600mm double panel) and left the kitchen one open and left the entrance rad open, the entrance rad started to get hot, the kitchen started to get hotter than before so turned that one off and the entrance rad got hotter, which means to me there is no airlocks, here's some info on the pipe work the entrance is on 10mm pipework the kitchen is on 8mm pipe work, the sitting room is on 15mm pipe work. Being a disabled pensioner (72) I am at my time of life not able to rip out the dead legs and increase the size of the pipe work, I could shut off the kitchen rad as the kitchen is open to the sitting room so the sitting room rad would warm up the kitchen, I could also put TRV's on the bathroom towel rails as they can get pretty hot and the room stat is in the sitting room ( a data term box) which means that when the bedrooms and the bathroom reached the desired temp they would close down resulting in an increased flow to the down stairs dead legs but probably not enough to heat up all the downstairs rads. As I have always maintained the pumps I selected to run my system are not suitable ( silly me) what do you think about using one of the commercial pumps that I listed, i can vividly remember years ago I did put a big pump in the system ( i suppose I could find out which one but it would take me a long time) I even had to manufacture a plate with rubber mountings for the vibration noise and special connection hoses to the system) it worked ok, that's all I can say, anyone want to buy a Grundfos Alpha 3b 15 50/60 bought 4 months ago and has only just started to be used (no heating over the summer months)

 

[rcpilot]

You are pumping practically NIL as you can see from the pump curve that the flowrate at 5.9M is 0.
The pump power is 22/23kw, you should see this displayed and also the flowrate showing 0 M3/hr, so you might note these.
Also just shut the pump outlet valve for 10 secs or so with it running and the above numbers 5.9M/22kw/0.0M3/hr should remain the same.

 

[John.g]

Have a careful look at the pump power as iis possible that its pumping 0.65m3/hr (10.8LPM), if so the pump power will be 34W so carefully note this and then briefly shut the pump outlet valve and again note the power.

 

[rcpilot]

so what's the answer, if you mean change the settings how do you do it (if you have read my last reply you should understand)