Rads cold on bottom

[Oldone]

Please help.

My rads are cold on bottom and warm/hot on top.

13 rads in total 11 new 2 older ones, I put in Heating myself with Worcester LPG boiler 95k btu and have 3 port valve and pump. Stat's etc..
HW only is fine, CH only rads get really hot but not as hot as I think they should get. When HW& CH are on rads stay warm only.

I am pretty sure I do not have any sludge in system as I have flushed out old rads when I re installed them..

Thanks in advance for any help.[/b]

 

[ChrisR]

You need to get the burner pressure checked at the boiler to make sure it's running at full throttle, as it were. With mains gas you can measure consumption at a meter... DP will know!

When the CH & HW are on together is the boiler cycling on and off, (on its internal thermostat), or on continuously?

I assume you've checked the pump speed is at max, if it's adjustable. What boiler is it???????????

 

[brumylad]

Have you sized the pipes correctly. from memory I think 15mm pipe will only serve 16000 BTU of heat requirement. With 13 good sized radiators plus HW part of the heating circuit will need to be in 22mm.

 

[Oldone]

Have you sized the pipes correctly. from memory I think 15mm pipe will only serve 16000 BTU of heat requirement. With 13 good sized radiators plus HW part of the heating circuit will need to be in 22mm.

I have run 22mm right up to 1 mtr or closer to each rad and then reduced to 15mm.

Thanks

 

[Oldone]

You need to get the burner pressure checked at the boiler to make sure it's running at full throttle, as it were. With mains gas you can measure consumption at a meter... DP will know!

I think you may have the answer here Thanks Chris...

When the CH & HW are on together is the boiler cycling on and off, (on its internal thermostat), or on continuously?

continuously?

I assume you've checked the pump speed is at max, if it's adjustable. What boiler is it???????????

I have set it at 2 if i set at 3 all stays cold..

 

[Oldone]

Gentlemen

thanks for all your help on this subject..

The rads are now all piping hot!!

It turn out the burner pressure screw needed attention .!!

Cost me £20.00 not a bad deal I think..

Boiler was Worcester 19/24 cbi/lpg.

Thanks again for all your helpful suggestions....