Balancing a Single Pipe System

[WHPES]

Hi. Have been asked to look at a single pipe system which is out of balance. Don't have much esperience in them. The first two radiators on the circuit are hot as are two upstairs. The rest are cold or lukewarm.

What is the best method of balancing such a system?

Should the pump be on a higher or lower setting?

Should I turn the boiler stat up?

Many of the radiators have TRVs fitted which I don't know if they are full bore as I know that reduced bore ones shouldn't be on a single pipe system.

Is it possible that some of the radiators are blocked? I have taken two off and rinsed out. Some sludge present but not vast amounts.

Any help would be appreciated.

 

[fuzzy]

Hi. Have been asked to look at a single pipe system which is out of balance. Don't have much esperience in them. The first two radiators on the circuit are hot as are two upstairs. The rest are cold or lukewarm.

What is the best method of balancing such a system?

Should the pump be on a higher or lower setting?

Should I turn the boiler stat up?

Many of the radiators have TRVs fitted which I don't know if they are full bore as I know that reduced bore ones shouldn't be on a single pipe system.

Is it possible that some of the radiators are blocked? I have taken two off and rinsed out. Some sludge present but not vast amounts.

Any help would be appreciated.

I have worked on many 1 pipe systems mate

they are notoriously difficult to balance. I worked on them in schools which have a very large bore pipe and oversized rads with TBOE connextions.
If your talking of a domestic house what are the pipe dimensions? has it ever been in balance? you normally start with all valves shut down apart from the furthest, then work back only opening the rads slowly, theres a few ways of going abaout it, let me know how you go on

 

[WHPES]

Should I set them to 11 degree differential using pipe thermometers or is this pointless for single pipe systems?

 

[justlead1]

Hi. When this type of system was installed it was not unusual to have rads luke warm. The main reason was, the legs to feed the rad was to long. Creating a greater frictional loss than the flow/return between the take off branches. On domestic work, in order to reduce this a wheel head on one end and 1/2" boiler union (69 I think) were fitted. However if its by-passing the rads, the temp drop between F&R back at boiler should not be that great? Assuming the history of the system suggests it did work at one time? Is the pump working at max efficiency.
I do recall a situation where a rad fitted in a bay window was piped for fitter convenience, with take off to rad approx 4 foot long in order to get water moving through the rad a 3/4"x1/2" reducer x two were fitted in the F&R between the two branches, in order to create friction and divert water through rad. ( on occasions a similar procedure was employed with a pair of mole grips) Be careful in adopting such a system as they make the phone ring a lot. Good Luck

 

[fuzzy]

Hi. When this type of system was installed it was not unusual to have rads luke warm. The main reason was, the legs to feed the rad was to long. Creating a greater frictional loss than the flow/return between the take off branches. On domestic work, in order to reduce this a wheel head on one end and 1/2" boiler union (69 I think) were fitted. However if its by-passing the rads, the temp drop between F&R back at boiler should not be that great? Assuming the history of the system suggests it did work at one time? Is the pump working at max efficiency.
I do recall a situation where a rad fitted in a bay window was piped for fitter convenience, with take off to rad approx 4 foot long in order to get water moving through the rad a 3/4"x1/2" reducer x two were fitted in the F&R between the two branches, in order to create friction and divert water through rad. ( on occasions a similar procedure was employed with a pair of mole grips) Be careful in adopting such a system as they make the phone ring a lot. Good Luck

could put swept tees on to help the water into the rad, the normall issue is the water just shooting past the rads. or the other thing iv done when really stuck is put an iline lock shield on the pipe under the rad. as u say presuming it worked at some stage it shouldnt be a design fault? has there ben any modifications?

Should I set them to 11 degree differential using pipe thermometers or is this pointless for single pipe systems?

can be diffcult, better start at first rad if your doing it that way and work through to the last. problem is you may struglle to get that drop across all of them, thats why i suggested starting at the furthest and just trying to get heat to them to begin with

 

[unguided1]

i am assuming that the system has no radiator bypasses, so you could remedy it by installing some or, the system is so old offer to upgrade to to a two pipe system, in the long term it will help with efficiency.

 

[WHPES]

An upgrade is out of the question - the guy is in his 80s and doesn't want to know.

 

[fuzzy]

An upgrade is out of the question - the guy is in his 80s and doesn't want to know.

your best bet is just trying to get heat round to all rads. Try to force it round using the LS valves. Ty turning the boiler stat up, is the boiler producing enough heat in the first place? does it need servicing? what is the return pipe temp like when its been on a while? if hot the prob is the system bypassing the rads. if so refer to my ealier advice and let me know if you manage to improve the system

 

[WHPES]

Does the pump want to be on a low or high setting?

Is it worth taking all the radiators off and rinsing them out or is this a waste of effort?

Obviously if I fail to make any difference in the system I can't charge for the work and I fear I may be days on it and get nowhere.

 

[fuzzy]

Does the pump want to be on a low or high setting?

Is it worth taking all the radiators off and rinsing them out or is this a waste of effort?

Obviously if I fail to make any difference in the system I can't charge for the work and I fear I may be days on it and get nowhere.

id try it on low to try to give gravity a chance to get hot water into the rad. id only take off 1 rad to see if it made a differecne. Speak to client and give him options, id charge for 2 hours work and see if it brought about improvements. then tell client again and see what he ssyas

 

[WHPES]

I've been on it this afternoon. The system started having problems before Christmas with some of the radiators failing to heat up properly. The client had a plumber out then who connected a hosepipe to a rad tail and blew cold water round the system and out through a drain cock, scratched his head and reversed the pump, pushing hot water out of the bottom of the boiler and backwards round the circuit. One of the rads which was cold (at the end of a loop) was then hot but others were cold.

The rads which were cold were fitted with monodirectional TRVs and when I put the pump back on the correct way most ot these worked. Two rads on the circuit have the TRVs the other way round and I am hoping that reversing them will get those rads to work now.

The boiler is in a garage and controlled only by a simple timeclock. The 28mm pipe goes off into the corner of the kitchen (hidden) where I assume it branches off in 3 ways - a 28mm pipe to the cylinder where the F&E pipes are joined at the top and bottom of the coil respectively. A Drayton 552 valve is fitted after the bottom of the coil. I can't find this in my catalogue but I assume it's a bypass valve of some sort to restrict the amount of hot water flowing through the cylinder coil.

Going back to the kitchen, there appears to be a further two loops - one for the upstairs heating and one for the downstairs. At the rear of a cupboard where the CH pipe for upstairs rises there is a gate valve which at present is fully open. I am assuming there is also one for the downstairs loop but as yet I have been unable to locate it.

Another question is, as one of the rads is poor between two good ones on the same wall, I am assuming there is some form or restriction either at the valve or lockshield, or at the Tee where it connects to the single pipe loop. Is this likely to be the case? I have already had the rad off and swilled it out so I know it is not the rad itself.

I also had the pump on max setting for a while and heard a lot of air rushing round which eventually settled at the top of some of the rads.

Is it worth putting some Fernox F3 in the system prior to draining or is this a waste of effort. Obviously I can't powerflush as its a single pipe system.

I need to replace most of the lockshields as they are so old they start leaking once you turn them and when they are off I'll poke some wires down the pipes to check for blockages.

 

[fuzzy]

I've been on it this afternoon. The system started having problems before Christmas with some of the radiators failing to heat up properly. The client had a plumber out then who connected a hosepipe to a rad tail and blew cold water round the system and out through a drain cock, scratched his head and reversed the pump, pushing hot water out of the bottom of the boiler and backwards round the circuit. One of the rads which was cold (at the end of a loop) was then hot but others were cold.

The rads which were cold were fitted with monodirectional TRVs and when I put the pump back on the correct way most ot these worked. Two rads on the circuit have the TRVs the other way round and I am hoping that reversing them will get those rads to work now.

The boiler is in a garage and controlled only by a simple timeclock. The 28mm pipe goes off into the corner of the kitchen (hidden) where I assume it branches off in 3 ways - a 28mm pipe to the cylinder where the F&E pipes are joined at the top and bottom of the coil respectively. A Drayton 552 valve is fitted after the bottom of the coil. I can't find this in my catalogue but I assume it's a bypass valve of some sort to restrict the amount of hot water flowing through the cylinder coil.

Going back to the kitchen, there appears to be a further two loops - one for the upstairs heating and one for the downstairs. At the rear of a cupboard where the CH pipe for upstairs rises there is a gate valve which at present is fully open. I am assuming there is also one for the downstairs loop but as yet I have been unable to locate it.

Another question is, as one of the rads is poor between two good ones on the same wall, I am assuming there is some form or restriction either at the valve or lockshield, or at the Tee where it connects to the single pipe loop. Is this likely to be the case? I have already had the rad off and swilled it out so I know it is not the rad itself.

I also had the pump on max setting for a while and heard a lot of air rushing round which eventually settled at the top of some of the rads.

Is it worth putting some Fernox F3 in the system prior to draining or is this a waste of effort. Obviously I can't powerflush as its a single pipe system.

I need to replace most of the lockshields as they are so old they start leaking once you turn them and when they are off I'll poke some wires down the pipes to check for blockages.

Hi,

Is the drayton valve a mechanical cylinder stat, like a trv on a cylinder?


Sounds like youve sussed most of it. I presume the one rad not getting warm just needs to be balanced but its not uncommon to have 1 or 2 thats difficult to sort. Check the valves as you say there may be an issue, swap both if in doubt, then if it dont work you need to force the water into the rad somehow. Either a swept tee sweeping the water in or a LS inline to force the water through. Both pretty extreem so ensure you cant sort it with new valves and balancing alone first, good luck

 

[WHPES]

Update - I spent a day on it. I connected the powerflusher up and blew out all the pipework, got loads of muck out, took each rad off and flushed it out, replaced all the failing lockshields, refilled and bled the system. I discovered the boiler was overheating so the serrvice contractor replaced the stat. The system was working perfectly again with all radiators getting hot.

Then this morning the customer phones up to say that since last night (Sunday) ths downstairs radiators have gone cold again. The system had been working fine until December when the problems started.

I am really at a loss as to what to do now and am reluctant to spend any more time on it as I have spent the best part of 3 days so far and got nowhere.

 

[WHPES]

Update 2 - the guy said he's been messing about long enough with it over the years so can I come along in the Summer and rip the single pipe system out and replace it with a modern pumped two pipe system, new rads and zone controls!

 

[LIFES A GAS]

I would start by checking if you have circulation to every rad by turning all the others off, do this to every one of them in turn, then you will know if you have a blockage's anywhere, the problem with one pipe circuits is the water entering a rad has had it's flow temp reduced buy any rads in the circuit before it as the cooler water leaving rad 1 mixes with the water flowing to rad 2 and so on, so the water entering the last rad is much cooler than the first. You need to reduce the flow through the rads closest to the boiler, start by turning off the lockshield valve and then open it just 1/4 turn (more or less depends on make), you may need to opens others a little more the further away from the boiler they are until the rad furthest away may need it's locksheild valve fully open. Regarding pump speed and boiler temp: faster speed is not always better, so set on medium speed, boiler temp depends on wether the system has any form of temp control on the HW cylinder, if it's a gravity HW system the hot water would be too hot if the boiler temp was set too high, hope this helps,
Martin
Sorry, didd'nt read page 2 before commenting.

 

[Blackcatgas]

Update 2 - the guy said he's been messing about long enough with it over the years so can I come along in the Summer and rip the single pipe system out and replace it with a modern pumped two pipe system, new rads and zone controls!

Winner!, it makes you wonder if its ever worked correctly.