adding a replacement rad.

[Mik]

Hi all. Hope you can give some advice on the following. Son's victorian house in on three levels. Existing system on a combi . with 12 rads. The ground floor level is fed from the 1 st floor with risers and droppers to the rads on the two levels. the last rad on the system was installed in 10mm micro bore . The rad did not get hot at all. (luke warm). I have removed old pipe back to 1 st floor level and propose to drop new 15mm to the system. Should have said this micro bore was only on the last rad in the system. I assume an after thought done on cheap.
I had noticed prior to removal of rads for damp proofing work that the second on system to last rad did not get very hot . lets say warm. I assume that because the system is over the three floors that the pump is at its limits . Do you think that 22mm pipes would be a benefit on the this last dropper. I would say 4.00 metre each legnth for the flow and return. This last rad is also in the hall, and son wants as big arad as possible . I am not so sure . Any thoughts would be gratefully received. I plant to return to complete work for him on Wednesday . He lives 200 miles away so want to go with a plan. PS existing rads rating way below boiler capacity (Worcester) incl making allwance of 5000 btu for hot water.

 

[tinners]

Do as you proposed replace 10mm micro bore, fit new rad , thoroughly bleed the system and balance out the heating system and you should be good to go!

 

[Mik]

Thanks for coming back so quick. As this system is over three floors what would be the best way to balance the system. I have noted that some of the rads have thermo. valves on them others not. I assume you would work away from the nearest to boiler, but what would be best when I get to the riser to the third floor that is half way along the mains flow and returns on the first floor system.

 

[SimonG]

Just take it rad by rad and take off the trv heads before you do it. If you use the search function on the forum for balancing there's plenty of help on there.

 

[Citiheat]

Hi Mik. It is unusual to find a radiator piped in 10mm on a system where all the other radiators are piped in 15mm. This may suggest that it was an after thought, as you suspect. If there are other cool radiators, and they are the more distant ones from the boiler, then I would first suspect that the system hasn't been balanced correctly, then that there is oxide sludge in the system, then that the pipe work is incorrectly sized. It is unlikely that a combination boiler pump is underpowered. If you replace the radiator pipe work with 22mm, you will possibly have a lovely warm radiator, but then you will have to shut off most of it's flow with the lock shield valve, as many of the other radiators will have no flow at all. You have to share all of the power of the pump between all of the radiators. If the pipe work is too small, then it may not be incorrectly sized at the radiator, but at the main pipes coming out of the boiler to the various floors. You can only get so much heat through a certain sized pipe for a given distance. In summary. Don't run 22mm pipe to a single radiator unless it is a very big radiator. Balance the system before you do anything. Don't forget that if it worked before, then it is not the pipe but something that has happened just before the radiator went cool. ie dented pipe. Lockshield valve turned down. Thermostatic radiator valve sticking. Black oxide sludge (Rust). All other radiator lockshield valves fully open or not balanced correctly. Be careful with a combination boiler. It is probably a sealed system, so relies on the system being at a given pressure. turn the boiler off first. freeze the pipes to be worked on or drain the whole system. Bring the system up to pressure before turning on the boiler - even if you have only vented a radiator. When you have finished and are sre that your work is correct and that there are no leaks, add inhibitor. Check the system pressure regularly for a couple of weeks afterwards - just to be sure - and maintain a system pressure of 1.2 bar, or in the middle of the green area on the dial if no numbers, when the system is COLD.

 

[Mik]

many thanks for yuor Time everyone. I will take on board the comments. It was only the last rad on sytem ( the one I am going to replace and repipe) and the next to last that has the heat up problem. I rekon that with a bit of careful balancing I may well be able to eake out the little bit extra flow I need.

Great site , great people. many thanks Mik

 

[SimonG]

Have a good go at the blancing before you change the 10mm, might save you a job.

 

[Citiheat]

Number the radiators from the top of the house to the bottom. Use sticky notes.
Make sure that the system pressure is correct.
Check and top up the pressure every time you let air out of a radiator. It should be 1.2 bar or in the middle of the green.
Make sure that all of the thermostatic valves are working. Turn them all off except the top floor. See which radiators get hot over all three floors and make notes.
Make sure that all of the radiators that are off remain cool and make notes.
When that is done properly turn on all the middle floor radiators. When they are all on, and not before, turn off all of the top floor radiators. See which middle floor radiators get hot and make notes.
When that is done properly turn on all the ground floor radiators. When they are all on, and not before, turn off all of the middle floor radiators. See which ground floor radiators get hot and make notes.
Check your notes and see which radiators are not working at the correct setting and make a list of them. These are your problem radiators to be sorted out later.
Turn each lock shield valve off (Clockwise, like turning a tap off) and then open it up as follows: Top and bottom floor 1 1/2 turns. Middle floor 3/4 of a turn. This to be done one radiator at a time.
Run the heating with the room thermostat up full.
After 30 to 60 mins, go to all of the radiators and feel them, again one at a time starting at the top of the house.
Note the radiator and if it is very hot all over, warm all over, hot at the top half, hot at the top, cold at the top but hot at the bottom or cold and make notes.
If it is very hot all over, turn the valve down 1/4 of a turn and make notes.
If it is very cold all over open it 1 turn and make notes.
If it is hot at the top and cold at the bottom open it 1/4 of a turn and make notes.
Allow the system to get cold and repeat.
The room with the room thermostat in should not have a thermostatic radiator valve, if it has, set it to maximum and ensure that the radiator gets hot when the system is hot. works.
Remember, plumbers, heating engineers and electricians are very carfull and methodical chaps for a very good reason. After all, they are still alive and hopefully in business.

 

[Mik]

Thanks for yuor help. certainly learnt a lot. Mik

 

[Citiheat]

It's a pleasure Mik. Remember, most combis are killed by low system pressure.

 

[Citiheat]

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