Rayburn central heating, what pipe diameters?

[dutchboy]

Hi there,

I really, really, really want the answer to this question to be 15mm, but I suspect not!!

I have a Rayburn 460k twin pressure jet which I am installing on a 50' Dutch Barge to feed a small hot water cylinder, two radiators and a towel rail. This is a modern Rayburn with pumped hot water circulation and electrical supply with thermostats and timers. I want to use 15mm copper pipework for reasons of cost and particularly space..... this is very different to a domestic installation involving going through steel bulkheads, with awkward spaces and so forth.

I have read the manual which clearly stipulates 28mm pipe on the send and return to the hot water cylinder and 22mm to the radiators. I have read lots on the internet that these pipe diameters must be adhered to, and lots of advice against using 15mm, but little by way of detailed explaination.

It would be infinitely easier for me to install 15mm pipe everywhere, including reducing the 28mm outlets on the rayburn immediately down to 15mm for the send and return to my hot water cylinder as well as for the rads. However it would be a nightmare to install all the pipes wrongly to find it doesn't work and needs redoing with larger pipe.

And my question is....... why not 15mm! What exactly will happen if I use 15mm pipework? And if there are any pitfalls can this be overcome by some other means instead of increased pipe size.

Many thanks for any help,


Andy

I have read the manual.

 

[dontknowitall]

28mm on flow and return - no ifs, buts or maybes!

If Y plan 28mm to pump, then zone valve, then 28mm to cylinder and 28mm reducing to 22mm for central heating circuit.
If S plan 28mm to pump, 28mm to each zone valve and 28mm to hot water cylinder and heating 28mm from zone valve but reducing to 22mm thereafter - I think Rayburns are better on a Y plan circuit. Certainly all the ones I've seen have this setup.

Radiators can be in 15mm or 10mm from central heating circuit flow to radiator and from radiator to (central heating circuit) return.

Just to make sure ... 28mm from Rayburn to airing cupboard and 28mm return.

 

[dutchboy]

Hi dontknowitall, thanks so much for helping.

I forgot to mention one other thing, the hot water tank is a marine item with a 15mm coil, does this mean I need a new hot water tank or can I spur from the 28mm Flow and Return circuit with 15mm pipe as if it were a radiator?

Just curious, what is the reason for the larger pipes advised?

Many thanks,

Andy

 

[dontknowitall]

Ah - sorry - can' answer those as I don't know!!

 

[dutchboy]

Hi, maybe I made it sound complicated!

I'm really just asking if the diameter of the coil in a hot water tank must match the diameter of the send/ return feed from a boiler. So if I'm using 28mm pipe on the send/ return, I presume the coil must also be 28mm?

 

[stani]

is this the Rayburn oil cooker with boiler?

 

[dontknowitall]

I think a coil in a cylinder is 28mm anyways.

 

[dutchboy]

Hi there,

This is indeed a modern oil fired Rayburn, twin pressure jets, one for cooking and one for central heating/ hot water. It has an electrical circuit board controlling port valves so that on the central heating side you can switch between water, heating or both. In a functional sense this just a normal modern boiler with an LCD programmable timer, with a cooker built in and a nice looking cast iron enamel body.

Regarding the size of coil in the water tank, it has 15mm connections, you can buy a tank with a coil any standard size fitting, 15, 22 or 28. My question is does anyone know if I need a new water tank when I'm supplying a 28mm feed to it and it has a 15mm coil.... can I for instance treat it like a radiator and spur off the 28mm send/ return loop?

Still looking for an answer to what will happen if I use 15mm pipe everywhere? I get that it's not recommended in the manual, but why?

Many thanks for posts,

Andy

 

[AWheating]

normally you will find that the connections and pipe size for an applaince are designed to remove the heat at the correct flow to ensure correct operation of the applaince (designed flow for the heat exchanger). If you did not remove the heat fast enough you will get overheating and find the appliance stays shut down for long periods untill it has cooled while the system wants to work. Also server overheating will cause damage.

 

[stani]

have you actually asked AGA/rayburn if the appliance is suitable for use on a barge. Usually its wood burners and then lpg heating and cooking, I know it looks the part but will it not be too big?