Central heating - what is a "one pipe system"?

[brettjbuckley]

We had some plumbers fitting a combi boiler recently one one of sounded very surprised when he discovered that our central heating was on a "one pipe system".

Can someone please enlighten me!?

 

[ollski]

Its an old and fairly awkward way of feeding your rads where the flow and return from the radiator are connected to the same pipe, therefore making the rads at the end of the run cooler than those at the start however well you balance it.

 

[doitall]

What Ollski has to say it a load ,of C by someone that don't understand a single pipe system or how it should work.

But saying that modern condensing boiler need to be on a two pipe system to reduce the return temperature

 

[ollski]

What Ollski has to say it a load ,of C by someone that don't understand a single pipe system or how it should work.

But saying that modern condensing boiler need to be on a two pipe system to reduce the return temperature

I think I understand what you are trying to say wheras you obviously don't understand what I have said. A one pipe system passes cooler water from the radiator back into the feed to the next radiator and so on meaning the last rad recieves cooler water. The water is pumped around the pipework heating the radiators by convection and therefore slower than a two pipe system. I am always willing to learn however so please enlighten me

 

[doitall]

What Ollski has to say it a load ,of C by someone that don't understand a single pipe system or how it should work.

But saying that modern condensing boiler need to be on a two pipe system to reduce the return temperature

I think I understand what you are trying to say wheras you obviously don't understand what I have said. A one pipe system passes cooler water from the radiator back into the feed to the next radiator and so on meaning the last rad recieves cooler water. The water is pumped around the pipework heating the radiators by convection and therefore slower than a two pipe system. I am always willing to learn however so please enlighten me

If installed correctly all the rads will heat evenly and at the same time, you are only pumping water round a single loop, containing possibly less than 15 litres, on larger system you can have several loops running back into a common return, the flows can be zoned with motorised valves, their own pump etc.

The return will be far hotter than a two pipe system which is a problem for condensing boilers, and it can't be chucked in as you can a two pipe system.

For Hospitals, schools and offices where steel pipe is used the single pipe system is still favoured, although for occupied risk buildings we are installing underfloor as a norm for new build.

 

[PEDANTICVINDICTIVEMAN]

Obviously need to spend spend spend like viv nicholls to get the best economy from your condesing blogger and change to a two pipe system, you might even get your money back in about 50 years.

 

[blahblah]

My twopenneth says the temperature must reduce the further along the loop you go else there can't be any heat emmitting from the rads or the pipe. Design guide says rad size should be adjusted up accordingly. Can't really control the temp differential at the boiler though becuse it unrestricted and virtually convects through the rads.

 

[doitall]

My twopenneth says the temperature must reduce the further along the loop you go else there can't be any heat emmitting from the rads or the pipe. Design guide says rad size should be adjusted up accordingly. Can't really control the temp differential at the boiler though becuse it unrestricted and virtually convects through the rads.

And what happens with a two pipe system, each rad takes a bit of the heat from the pipe, leaving slightly less for the next.

Sorry on that note there's no difference.

 

[kaboom]

But its not putting cooler water back into the pipe that will feed the next rad, its going to the return. Only temp loss on the feed will relate to pipe length and insulation until all rads are fed?

 

[doitall]

But its not putting cooler water back into the pipe that will feed the next rad, its going to the return. Only temp loss on the feed will relate to pipe length and insulation until all rads are fed?

But depending on the fittings used only 10% ish will enter the rad the same as a two pipe system, whereas a single pipe will complete the circuit far quicker than the two pipe.

 

[kevplumb]

the pipework loop is pumped the rads draw their water by convection

 

[doitall]

the pipework loop is pumped the rads draw their water by convection

Not if you use pitcher/sweep tees, tounge tees, or injector tees.

A single pipe has half the water of a two pipe, it will therefor heat up twice as quick.

 

[kevplumb]

shoe menders
a two pipe system is pumped if the boiler is man enough it will heat quicker as the flow is forced

 

[doitall]

shoe menders
a two pipe system is pumped if the boiler is man enough it will heat quicker as the flow is forced

So a 1 pipe system but with less water.

 

[kevplumb]

A single pipe has half the water of a two pipe, it will therefor heat up twice as quick.

nuts

the rads are fed by injection or convection depending on which way you go