System design advice please!

[Biggles..]

Part of the problem with this boilers design is the narrow water ways within the low content heat exchanger added to the fact the boilers connections are only 22mm on the larger models.

Now we all know that 22mm is not the correct sized pipe for nearly 40kw therefore the recommendation to increase the pipesize is to the systems advantage,the boiler is irrelvent,well nearly.

Obviously we get it wrong when we fit these as having installed over 50 of this type I've yet to struggle with f and r temp related issues.
On the other side,all the big heatings we design and instal with 4inch primaries(no header single boiler) according to spraggo are all wrong when the boilers only have 2inch tappings.
Suppose I would struggle with a 38kw boiler as it's less than 10% of the output where used to working with.

Onetap is correct where he tells you to take the horwater as a seperate take off off the header with it's own pump,therefore you have shunt pump(15/60), hot water pump (15/50), heating pump could now be 15/60 as you've got rid of the boilers 40kpa or I'd be inclined 25/55.
You could fit a magna upe25/55 to the heating which will react as the valves close etc.

 

[spraggo]

primaries(no header single boiler) according to spraggo are all wrong when the boilers only have 2inch tappings.



Hi Lee, sorry I did not mean to offend you with my prev comments, The point is that if you keep the 22mm flow and return pipes as short as possible befor dividing them to feed the hot water and index circuits, there would be no problem with them carrying the 40+Kw. This again can be proved by pipe sizing charts which indicates that if the flow and return pipes are less than 6m you should have no problem.

spraggo