Central heating system pipes advice

[splshirts]

The radiators in my three bed detached house did not seem to be heating up the house adequately and I didn't think they were getting very hot. The only one that seemed to be working well was a new style double convector radiator which is very close to the boiler. I replaced three of the old style doubles with the new convector doubles in the hope of getting a similar level of heat from these.

Unfortunately the new radiators are not getting very hot at the top and are stone cold at the bottom. I have a magnatec central heating filter and a cleaning fluid was run through the system so it shouldn't be sludge (plus the radiators are new and they have never got hot). I have Bosch boiler cover so they came out and had a look but the boiler appears to be working fine.

The pipes we have are 5mm copper which the engineer thought were too small for the system but he doubts they would be causing such a problem. There has been some minor alterations (radiators removed/ re-positioned) done on the property before I moved in and the engineer did wonder if the pipe circuit wasn't efficient. He did say he was only guessing though and a plumber would know better.

So, any ideas at all would be a great help? Also, if it did come down to altering the pipework, is there any indication roughly how much this would cost.

Thanks very much for reading and offering any advice, it is much appreciated. I have my first child on the way in February so if we could sort it out before then it would be bonus

Edit: I forgot to say that the hot water that also comes from my boiler gets very hot so there is no problems heating the water.

 

[Gray0689]

Firstly are you sure the pipes are 5mm??
When you turn your heating on does your hot water heat at same time or can you have it on independently

 

[splshirts]

Firstly are you sure the pipes are 5mm??
When you turn your heating on does your hot water heat at same time or can you have it on independently

No, I haven't measured the pipes myself - although they do look smaller than standard. The house was built in the 70s and apparently a lot of the pipes were smaller then.

Yes, the heating and hot water can go on together or independently and in both cases the hot water from the taps is very hot.

Thanks

 

[stevetheplumber]

first check there is flow to both sides of each rad t5urn of both valves remove airvent slowly till it stops running then open each end in turn catching the water from the now open vent in a bucket if you have water from both ends of all rads turn every radiator in the house of except one of the ones that doesnt work and run heating and report back what happens

 

[rawr]

hot at the top cold at the bottom? sounds like sludge to me, going down the flow but not returning before overheating? again. sounds like sludge. rekon the small diameter pipework is really aggravating the problem. turn off the rad that's getting hot to try force the heat elsewhere.

 

[splshirts]

hot at the top cold at the bottom? sounds like sludge to me, going down the flow but not returning before overheating? again. sounds like sludge. rekon the small diameter pipework is really aggravating the problem. turn off the rad that's getting hot to try force the heat elsewhere.

I turned off the rad that was hot and no obvious difference. I had the heating on for 7 hours yesterday and after that, the rads were all reasonably hot apart from the bottom 1/4 of the radiators which were lukewarm.

The radiators are new and the heating system was flushed before they were installed, has been flushed since (with inhibitor added) and a cleaning fluid put through it plus I have a magnatec filter. I obviously can't rule out sludge but I would have thought these measures would have prevented enough sludge settling at the bottom of new radiators to cause this issue?

Cheers

 

[splshirts]

first check there is flow to both sides of each rad t5urn of both valves remove airvent slowly till it stops running then open each end in turn catching the water from the now open vent in a bucket if you have water from both ends of all rads turn every radiator in the house of except one of the ones that doesnt work and run heating and report back what happens

Now sounding like a complete idiot I know but - you don't mean the bit too bleed the radiator? I have done that with them all and water comes out straight away.

Do you mean the bits at the bottom feeding into the pipes? If so, ill give that a go - how easy is it to uncouple? Cheers