single pipe heating system

[alant]

I just wondered if there is any cunning way of improving the performance of a 'single pipe' heating system (ie. A single pipe runs around the boat with both sides of each rad connected to that single pipe) without adding a second pipe and repiping the rads to this in the 'proper' way ??

[alan_fincher]

Horrible things, but you probably know that!

 

Had a house with one, and it never really worked.

 

Is it the type where the water has to flow through each rad, so that you can't shut one off without stopping the entire circuit? Or is it the type where a pipe goes past each rad, with a tee at each end, such that if you shut a radiator valve water will still circulate in the rest of the circuit ?

 

If the latter, it can help to add a valve in the "bypassing" bit of the pipe, so you can throttle back the flow there, and force more through the rad. It's still a difficult balancing act, though, IMO. The correct solution, as you have guessed, is to run a second pipe.

[David Schweizer]

For a single pipe system to work anywhere near effectively, the delivery pipe really needs to be 28mm (old 1") with 15mm tees for the radiators, each radiator must have a bypass if valves are fitted, and the pump needs to be set on a fairly high setting to increase flow, although this can cause problems with excess head of warter, leading to a constant flow of water into the header tank.

 

If the delivery pipe is less than 28mm, and certainly if it is only 15mm, I would take up Alan's suggestion and fit a second return pipe, of the same daimeter as the flow pipe, 15mm for both will be fine.

[Machpoint005]

A pump?

The amount of heat put out by the system can't be increased without a boiler (or back boiler) upgrade, but you have some control over where the heat comes out. Hence, a pump, instead of relying on convection alone.

[alant]

Horrible things, but you probably know that!

 

Had a house with one, and it never really worked.

 

Is it the type where the water has to flow through each rad, so that you can't shut one off without stopping the entire circuit? Or is it the type where a pipe goes past each rad, with a tee at each end, such that if you shut a radiator valve water will still circulate in the rest of the circuit ?

 

If the latter, it can help to add a valve in the "bypassing" bit of the pipe, so you can throttle back the flow there, and force more through the rad. It's still a difficult balancing act, though, IMO. The correct solution, as you have guessed, is to run a second pipe.

Hmmmm, It is the latter type, I did wonder about that....I considered inserting a section of 15mm pipe between the 2 rad connections, which would constrict the flow without the possibility of blocking the whole thing off should the rad valve be accidentally turned off, and I could take off the valve knob to prevent it being turned off 'casually'...there's only 2 main rads so it would be an easyish job. I could try it on one rad to see if it works, if not not a big problem to reinstate??

[Proper Job]

The entry to the rad should be at the top of the rad. The exit at the bottom. The rad acts as the heat sink and induces flow through the rad.

 

I often see people who have done them with bottom entry/exit and they wonder why they won't work

[alant]

The entry to the rad should be at the top of the rad. The exit at the bottom. The rad acts as the heat sink and induces flow through the rad.

 

I often see people who have done them with bottom entry/exit and they wonder why they won't work

 

Ahhhh ! yes both connections are at the bottom of the rad, so if the pipe is extended on one side, to a top entry, I assume the nearest side to the flow from the boiler, then you reckon i stand a good chance of a better flow ??

[kerching]

Just to clarify. You have got one pipe from you boiler (flow pipe). Does this run down one side of the boat and return down the other side back to the boiler or back down the same side of the boat?

[alant]

A single pipe runs from the boiler down one side of the boat, across the front under the front doors, and back down the other side of the boat. The rads are connected at both ends to this single pipe, and both connections to each rad are at low level.

[kerching]

In that case then it probably is a big job to convert to a two pipe system. You would be better doing, as previously stated, making the flow to the top of the rad.

 

As a quick fix you could try to balance the system by turning off all the lock shield valves then just open the first valve a half to a full turn, the next valve a full turn to one and a half turn etc to all the valves. Very much trial and error but it may help.

 

Edit :- Sorry I have just read the post were you state there is no "bypass" for each rad, must have over scrolled. Quick fix won,t help. In fact it will make it worse.

 

Rip it all out, weigh it in and put a two pipe in.

Edited March 5, 2009 by kerching

[Proper Job]

Ahhhh ! yes both connections are at the bottom of the rad, so if the pipe is extended on one side, to a top entry, I assume the nearest side to the flow from the boiler, then you reckon i stand a good chance of a better flow ??

Its all about inducing a convection current in the system - more importantly - across the radiator.

 

When both inlet and outlet pipes are at the same level (top or bottom) there is negligable natural convection taking place. With one at the top and the other at the bottom a natural convection current establishes it self very quickly.

 

Take a look at any old single pipe heating system with cast iron rads. Inlet at the top, outlet at the bottom.

[RobinJ]

Ahhhh ! yes both connections are at the bottom of the rad, so if the pipe is extended on one side, to a top entry, I assume the nearest side to the flow from the boiler, then you reckon i stand a good chance of a better flow ??

I don't quite understand the argument here!

I have a single pipe system without any radiator valves, hot water flows in at the bottom, hot water rises to top of radiator, cold water flows out at the bottom the other side, only drawback is it takes a while for the last radiator to get hot. Works by convection, but I have a pump to boost it if necessary.

[Big COL]

Horrible things, but you probably know that!

 

Had a house with one, and it never really worked.

 

Is it the type where the water has to flow through each rad, so that you can't shut one off without stopping the entire circuit? Or is it the type where a pipe goes past each rad, with a tee at each end, such that if you shut a radiator valve water will still circulate in the rest of the circuit ?

 

If the latter, it can help to add a valve in the "bypassing" bit of the pipe, so you can throttle back the flow there, and force more through the rad. It's still a difficult balancing act, though, IMO. The correct solution, as you have guessed, is to run a second pipe.

 

Spot on Alan

 

The most efficient system for a single pipe loop is to use fin rads to the maximum amount possible.

Aldi boilers are good on single loop systems, maximum heat coupled with a very slow pumped circulation via the aldi stirrer motor type pump.

Edited March 7, 2009 by Big COL

[DHutch]

Robin i presume you are talking a single pipe system where the outlet from one rad goes onto the next, round a big ring

- This is what we have on emilyanne, but is diffrent to what is being talked about here, where there is a (singe) unbroken loop of pipe from which the radiators or branched off.

 

See the first image on this page. http://www.diydata.com/planning/central_heating/pipework.php

 

 

But to answer the OP, i would suggest eather adding said valve, to force a presure diffrence and flow across the radiator, given theres only two. Or else moving the rad feed (pump side) to the top so the radiator flows by convection.

- Single pipe systems work find if done right, although are slightly less dynamic in coming on and off.

 

 

Daniel

[RobinJ]

Robin i presume you are talking a single pipe system where the outlet from one rad goes onto the next, round a big ring

- This is what we have on emilyanne, but is diffrent to what is being talked about here, where there is a (singe) unbroken loop of pipe from which the radiators or branched off.

I agree, its the bit where it needs to be fed to the top of the radiator thats confising me!

Surely the principle is the same, hot water rises into the radiator (controlled by a valve if needed), but why should it need to go to the top?

I would think that the flow would interfere with the convection!