2 hours for rads to heat up

[Crakkers]

Hi

I have a Vailant Ecotec system boiler, 24kw feeding 10 rads in total, plus heating the water cylinder. I live in a typical 1930's 3 bed semi.

Upstairs rads, if on, heat quickly and to full power. In fact out of 4 rads upstairs only two are ever on, we prefer cool bedrooms!

Downstairs rads take up to 2 hours to heat fully, one never gets warmer than "not cold".

I have balanced the system as best as I can via the lock shields, having them open at the minimum setting to allow each rad to heat fully. As a result some lock shields are hardly "on" at all.

I have the boiler set as follows, water temp set to 60 degrees and rad thermostat set to 70, which should be well high enough??

The boiler has been recently serviced and a new pump was fitted. I dont believe the system is clogged with sludge as when I have done any work, water appears clear and I always add inhibitor when refilling.

Ideas?

Crakkers

 

[John D v2.0]

Blockage in the pipes to downstairs? What happens if all rads are off upstairs?
Can you flush through the downstairs rad circuit freely?
24kw seems really excessive unless you live in a barn without doors.

 

[Crakkers]

Slight improvement in heat up times.

I was thinking of replacing the 8mm microbore with 15 pipe in case of blockages. But I would be surprised if a blockage as two rads do heat fully after the two hours, but as i said, one, and ironically this one is a new rad piped with 15 pipe stays cool.

??????????????

 

[DP]

Run central heating without hot water and see if that makes a difference

 

[Crakkers]

OK will try that tonight, but thinking about it, I have the CH switched on at 5pm and the hw does not come on till 7 ish so thats 2 hours without water and poor heating. In the morning both come on at 6 and similar coolness is the result. HW BTW is very hot!

 

[John D v2.0]

Slight improvement in heat up times.

I was thinking of replacing the 8mm microbore with 15 pipe in case of blockages. But I would be surprised if a blockage as two rads do heat fully after the two hours, but as i said, one, and ironically this one is a new rad piped with 15 pipe stays cool.

??????????????

Double size pipe with the same flow volume would take 4 times as long to get the hot water to the rad.
But 2 hours is ridiculous. Does sound like a knackered diverter valve if the hw is always boiling hot
Is the pump on high? And the bypass on a higher pressure difference?

 

[Crakkers]

Double size pipe with the same flow volume would take 4 times as long to get the hot water to the rad.
But 2 hours is ridiculous. Does sound like a knackered diverter valve if the hw is always boiling hot
Is the pump on high? And the bypass on a higher pressure difference?

Thanks, getting technical now for a DIYer, Diverter valve? Bypass on a higher pressure difference?

Can you explain a little?

 

[John D v2.0]

I'm a diyer too!
Diverter valve is the thing that decides whether the water heated by the boiler goes to the radiators or to the hot water cylinder.
Sometimes you have one with 3 ports and sometimes two in parallel, one for each.

The bypass is designed so when all the radiators are off, the water can still move through the boiler and pump. So it opens to short circuit the flow and return when the water isn't going through the radiators successfully. It needs to be adjusted to be closed when the radiators are all on though. If you have a high restriction it might all be going through the bypass instead.