50mm Mdpe & Water Heater Central Heating

[Dave30]

I am currently upgrading the system in my house

It currently uses a Gas tankless water heater which provides around 35L/min

I would like to add a Central Heating system for 3 floors with weather compensation.I would like to use a Indirect Vented Combination Cylinder as a Buffer, to act like a combination boiler with a Gas Saver to improve economy. Was looking to use a Danfoss Controller to control temp,zones and pump.

I have come up with a design :

http://tinypic.com/r/fk1f9x/6

I cannot add a accumulator as the way the loft is designed with hatch opening, its impossible to get tanks upstairs and no space on the lower levels.

As I also need to change the mains from lead to MDPE. I was going to run a 50mm MPDE to compensate the flow rate which is currently 12L/Min and I would rather oversize then under size as in the future I may add more to the house, currently running 2 weak showers and a slow filling bath. Thames water have told me that they will make the connection as I am replacing the existing lead pipe. I was wondering what is the best quality connections for inside the house.

I was going to go from 50mm MDPE X 42mm Copper and then T to make 22mm to the gas heater and 22mm for the rest of the house. But I cannot find a stop tap for 50mm poly x 42mm copper. I have found plastic stop taps but my confidence in them isn't that great

Any help or Advice would be much appreciated.

Thanks

 

[Norcon]

I don't thinks its complicated enough.
You seem to have the dhw supply as the re heat method for the cylinder which then supplies the primary system.
How does it get circulated between boiler and cylinder?
What controls the 4 way mixing valve and what make of valve is it?

I'm not sure what benefit the buffer fulfills? Especially with a controller of that caliber.

 

[swbjackson]

I think the best method is to get someone in that knows what they are doing instead of trying to mix incompatible technologies.

 

[mickyg]

unnecessarily complicated

edit: just looked again and its technically wrong anyway, it wont work.