You mean mathematically?. if a differential head of 3M results in a flow of say 13 LPM (like my heating system) and I increase the (pump) head to say 5M, the resultant flow will be the original Flow X the sqroot of the (newhead/oldhead).....13X sqroot(5/3) = 13X1.29 = 16.77 LPM.
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Discuss Central heating pump sizing in the USA Plumbers Advice area at PlumbersForums.net
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Thanks buddy. That makes sense now
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Although they both have this part number DAB 60161174, the images look different......the Amazon one is more expensive Andries than even look like it has the data display.....
Will phone PSD tomorrow and confirm, think this is my best hope, seems a very good price £62.39 inc free postage....any thoughts ? 1st image PSD 2nd image Amazon
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That’s the one on the left, curious how prices vary, £60-£150.....eBayera are an optimistic breed
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Problem is, I have just been advised this is a 180mm length pump whereas mine is 130mm, is that correct ?
The DAB3 appears to be a 8M pump hence the 180mm between centers so I would advise against this as it involves piping mods and drain down, also 130mm centers gives you more choice of 6/7M pumps.
While the Wilo or Dab Evosta2 (no display) will almost certainly give you the required head/flow I think you are better off installing a pump like a Grundfos UPS3 15-50/65 which is very powerful 6.5M pump which will satisfy your needs with ease. For example it will pump 33LPM @ 4.5M, Dab2, 33LPM @ 3M and the Wilo 33LPM @ 3.2m.
Unfortunately, this UPS3 does not display watts but not the end of the world as you really only need this as an aid to see if you have a pump problem or a restriction. By spending a few extra bob you can buy a nice little plug in energy monitor, I have a few and they are quite accurate, (see link) and use it like this.
I assume you intend to clean the existing pump head so before removal/clean, remove the pump lead and fit a 3 pin plug. ensure boiler off and any zone valves if fitted, latched open, plug in the pump lead to the energy monitor in turn plugged in to any convenient socket or extension lead, note the watts, remove plug, clean pump head and ports, then re measure power.
Depending on findings, if you do decide to install the UPS3 or whatever, do likewise, stick a 3 pin plug on it and you can then monitor its power in its different operating modes and then run the pump on the appropriate setting. When tests complete re install pump lead to wiring center.
One word of caution if removing the pump by opening the isol valve nuts, these can be extremely difficult to undo, I have change out a few pumps for neighbors and one of my own and have always drained down and removed the pump complete with isol valves, I then found it quite difficult to remove the pump valves even though I obviously renewed them with the new pump.
PS: fairly sure your pump has 130mm centers but best to measure up.
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Thanks for all the advice, sounds like the way to go.....will investigate the power to my pump, looks rather complicated, as this also had its wiring modified.....when an electrician came round a few years ago, he made some changes, involved lifting up the floor board to get access o the connections ( my dam extension buile
der
) found he had used a light switch as a junction box, now the new junction box in the immersion cupboard, but looks complex.....will have a careful look, taking photos as I go....all good fun what’s the LPM of the DAB3 ? Do like the idea of the displays, womder how it displays the flow, ant be a calculation as it doesn’t know the Delta T, must be an integral flow meter 
I don’t suppose a replacement pump comes with new valves, assume would have to be bought separately my CH pump iso valves have no handles, never have, can these be bought separately ? Be so much easier to isolate
der
) found he had used a light switch as a junction box, now the new junction box in the immersion cupboard, but looks complex.....will have a careful look, taking photos as I go....all good fun what’s the LPM of the DAB3 ? Do like the idea of the displays, womder how it displays the flow, ant be a calculation as it doesn’t know the Delta T, must be an integral flow meter I don’t suppose a replacement pump comes with new valves, assume would have to be bought separately
my CH pump iso valves have no handles, never have, can these be bought separately ? Be so much easier to isolateYour old pump isolating valves are probably 1/4 turn ball valves that you shut with a screwdriver (slot) or a allen key, nothing sticks out, but unfortunately they almost always leak after operation, you can easily buy new ones with gate valves.
It would seem that you can get a Dab Evosta3 with 130mm centres. it might be a 6.5/7M pump but you should ask your supplier if they have one, this will also be adequate IMO, the pump curves for all their models are in the link.
It would seem that you can get a Dab Evosta3 with 130mm centres. it might be a 6.5/7M pump but you should ask your supplier if they have one, this will also be adequate IMO, the pump curves for all their models are in the link.
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have ordered the DAB 3 21412 model, not sure which curve is applicable to the pump I ordered.... some websites don’t give the numbering, just the performance data, the site I bought mine from had some contradictory info, confirmed it was 130mm and 6.9m head by phone and has a 5 year guarantee not 3 as shown, hopefully they will change the info on their site...ordered it from https://plumbingsuppliesdirect.co.uk/dab-evosta-replacement-grundfos-circulating-heating-pump/ but the invoice is from STUART PLUMBING & HEATING SUPPLIES, but on their website it’s more expensive and have to pay postage
so assume PSD is owned by Stuart plumbing.....must be offering competition to their own company.....marketing strategy 
the pump seems to have numerous control options, what’s my best setting to start with ? And best setting long term....P.S. the pump iso valves are gate valves, not quarter turn, with a single square 1/4” approx post, no thread that I can see to hold a handle, can’t understand why they are sold like this, to shut off in an emergency, requires hunting around for an adjustable ( or normal ) spanner.....so much easier with a handle......maybe will replace them when I change the pump
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You have the correct type isol valves as the gland nut can be tightened up if any leak, so no need for renewal.have ordered the DAB 3 21412 model, not sure which curve is applicable to the pump I ordered.* some websites don’t give the numbering, just the performance data, the site I bought mine from had some contradictory info, confirmed it was 130mm and 6.9m head by phone and has a 5 year guarantee not 3 as shown, hopefully they will change the info on their site...ordered it from https://plumbingsuppliesdirect.co.uk/dab-evosta-replacement-grundfos-circulating-heating-pump/ but the invoice is from STUART PLUMBING & HEATING SUPPLIES, but on their website it’s more expensive and have to pay postage
P.S. the pump iso valves are gate valves, not quarter turn, with a single square 1/4” approx post, no thread that I can see to hold a handle, can’t understand why they are sold like this, to shut off in an emergency, requires hunting around for an adjustable ( or normal ) spanner..so much easier with a handle...maybe will replace them when I change the pump
Would suggest constant pressure, either CP2 or CP3 see below, answer to SJB.
Look at the pump curve on pge 25 in attachment which is for a 7M Evosta2, can,t find one for a 7M evosta3.
you will see that on constant pressure CP3 that the pump will maintain 4.8M from 0 flow, if the system demand is 1 m3/hr 16.7 lpm then the pump power is 35w, if a restriction in the system and the flow fell to zero then the power is 16.5w and so on in between. more later
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Which chart am I looking at?
Through common sense I imagine if there was a restriction on PP then the pump would modulate down and display a lower wattage?
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