New Radiator slow to get hot

[sime10]

Yes and Yes

 

[sime10]

Brain is now in overtime (don't wanna say sludge)

 

[shaunyab]

The old rads have been balanced to give the best flow and heat for that amount of rads. Depending on where you new rad lies, which may be at the end of a run (which is it by the sounds of it and how you have teed into them) then the existing rads will take the bulk of the heat leaving you one cool rad (the new one).
From what you have written I assume that when all the rads were turned off then the heat to the problem rad improved and maybe got as warm as the other rad which was left on.
If this is the case then the system may benefit from balancing, whereby the flow to all the other rads will be restricted slightly so giving your new rad a greater flow through it thus getting warmer.

 

[shaunyab]

Sorry sime you got in before me but I agree dont mention the sludge word.

 

[sime10]

Lol shaunyab you must agree with me everyone is powerflush crazy

 

[vessy]

It's definitely a flow issue for sure, the system water is quite clean and has always had a good dose of inhibitor (very hard water area) so i hope not sludge.

The rad tee'd from is not last in the system, in fact only about 5 meters away from the pump! As it's microbore aren't all radiators fed independently from the manifolds? The furthest rad is the other side of the house downstairs and that still gets hot.

When all rads bar 2 were turned off the new rad was still running about 50% behind the existing rad, and the existing rad outlet valve is only opened 1/2 a turn!!

My brain is in meltdown!!

 

[sime10]

My brain is in meltdown!!

Mine is too but I come in here to get away from work?
HOW SAD IS THAT

 

[vessy]

I normally stick to electrics, thought plumbing was easy as you can see the contents, how wrong could i be, stick to my day time job i think!!!!

 

[sime10]

Plumbing is always easy if you know the answer

 

[Steve__M]

Problem is the new rad (1200x500 double) doesn't get very warm, all the other rads are hot to the bottom after about 10 mins but this one is only hot 1/3 of the way down. Strangely the rad it is connected in parallel with still gets just as hot as before, just as quick!! all this is with the new rad valves fully open.

Removed the new rad and opened both valves into a bowl, got similar good flow from both.

The only thing i am worried about is the 10mm microbore (plastic) has been connected using inserts to help them seal, these have an internal diameter of just over 5mm, but why would i get good flow with the rad removed?

Really confused with this one, any help or advice would be priceless.

I am not a plumber, but I have this problem in my house. Bigger radiators need a bigger water flow, so adding your 1200x500 double is like adding four or five 500x500 single panel radiators. If you check the specs for plastic pipe, Hep20 says

"As a general precaution, Hep20 should not be used for a radiator output in excess of 1.5kW (about 5000BTU) unless proven by calculation."

and I think your radiator is above 1.5kW? Another plastic pipe manufacturer says their pipe is about equivalent to the same size copper...

Having said that, my "problem" radiator gets reasonably hot.