Central heating plan for stove and radiators

[jon]

Hi, I'm looking for some advice on a central heating system fed by a multi-fuel stove. The attached file shows what I intend to do with the majority of the work already completed. I've read some conflicting or unclear info from the web so hope someone can help. I guess the questions I have are as follows:

1. Can plastic be used within the system so long as heat can dissipate before entering the plastic pipe work such as through the tank, rads and copper pipe?

2. Will the combination tank be suitable or will it be too small to handle the heat output of the boiler?

3. Does the expansion tank have to be steel or copper rather than plastic (same goes for the float)?

4. Can the lower 5 radiators be run in 15mm plastic?

5. Am I missing anything that should be installed in a system like this?

Any advice would be appreciated. I also need to get it certified by building regs or a HETAS engineer (UK) to keep the insurance company happy and of course be safe.

Many thanks in advance

 

[BoilerMan]

When you say plastic do you mean PEX or something like PVC? PVC is not suitable for heating systems. PEX meaning crosslinked poly-ethelene is good for 180 or 82 some a bit higher. It must have an oxygen barrior if this is to be a closed system, which it looks to be in the pdf file. Also with the radiator connections you have I'd be worried about the last ones on the loop not getting flow, to solve this you could do a reverse-return setup, or a home-run manifold system. Google search hydronic reverse-return, and hydronic manifold system with radiators to see.

Taylor

 

[maple1]

I thought it looked like an open system.

There are things in there that I don't recognize - more details might help. Like, what is a 'combination tank'? And how big is it? What is the float you speak of?

Looks like there is a European slant to this system? Interesting...

 

[BoilerMan]

Yes it does look to be an open system with the "overflow" tank. I'm not too familliar with open systems. Still would pipe it reverse-return so you get flow to all the radiators eaqually even if by gravity. The larger pipe diameters that are needed to induce gravity flow usually offset the cost of the use of another circulator pump and small pipe (pex) for a closed system, but then you need electricity..... although there is one circulator already. Would need to br bronze if you keep the open setup.
Taylor

 

[jon]

Its designed as a vented system as I understand you shouldn't run an unvented system with a solid fuel burner.

We've used Hep20 plastic pipe which I'm guessing is a UK equivalent to Pex.

I've already installed 90% of the pipe work so changing to a reverse return wouldn't be possible. I was hoping to balance the radiators via lockshield valves which with some experimenting should work...

The combination tank is basically a cold water tank attached to the top of a hot water tank. An all in one unit with less pipe work to worry about. The one I bought was the smallest I could find as it's only to supply two hand basins. I believe its volume is 66lt.

I was thinking of getting a header tank like this which can handle higher temperatures than the standard plastic style. Would this be necessary?

Can I not use a standard pump on the cold return rather than a bronze on the hot?