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I'm thinking about getting a Magna3 which has auto adapt. If I'm using 28mm pipe would I get a 25-nn or a 32-nn ?
Discuss 15M pump required, one large Vs 2 small in series? in the Plumbing Jobs | The Job-board area at PlumbersForums.net
...but still 4.5M sounds very low.
Are you aware that you don't just add the flow resistances of radiators together to get the total.
The next question is what displacement rate do you require, which is a figure in litres/minute or cubic-metres/hour? You calculate it from the total amount of power you want the circulator to deliver. For the sake of an example, let's assume 40kW. For a 20°C temperature drop that would need a circulation rate of 1.7 cubic-metres per hour.
You then need to look at the pump curve to make sure that the combination of head and displacement rate lie within its operating curves.
Which literature were you looking at? There's nothing about heat exchanger resistance in the 40CDi Regular Installation Manual (I assume you are talking about the open vent version, not the system one). Did you take it from Technical Bulletin 48? If so the resistance of a 40kW CDi hex is about 3.5 metres, which isn't exactly small.used figure in literature for boiler, again very small.
I used the default figure in the sizing resistance in copper tube. It was tiny. 3.5M is much bigger. Yes looking at 40CDi regular, but with Robo kit. I thought 35CDi system was just too tight. In that case I would need 8.3M head.
I think 30kW would be too small, I also have 500L water cylinder with 20kW heat exchanger.
Reply to 15M pump required, one large Vs 2 small in series? in the Plumbing Jobs | The Job-board area at PlumbersForums.net
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