Please help

[scooby3]

We've had a set of luke warm/cold rads downstairs now for a short while, so after washing all the rads out and replacing the old 15mm piping with 10mm microbore piping and lockshield valves and trv's. We also fitted a new pump, (grundfos 15-50), but we still have luke warm/cold rads.

Upstairs rads are boiling even after a very strict balancing act on them all.

The boiler is quite old: an ideal standard e type cf conventional gas boiler.

Although now we get warm pipes going into the rads downstairs, the rads are still extremely cool.

I've also noticed that when the hot water fires up, the rads warm up to a comfortable heat. Any thoughts????

When the rads upstairs are switched off, the downstairs rads get extremely hot. But once balanced, go extremely warm......

Sorry it's all a bit mixed up, but i'm in the conservatory, and it's bloody freezing

Thanks in advance guys...

 

[chrishutt]

When the rads upstairs are switched off, the downstairs rads get extremely hot. But once balanced, go extremely warm......

Balancing means adjusting each rad so that all get equally hot. So you haven't balanced them properly.

when the hot water fires up, the rads warm up to a comfortable heat.

This suggests something fundamentally wrong, but without a lot more detail on the pipework layout and control system (motorised valves, etc.) it's difficult to say what.

 

[HarrogateGas]

For starters by replacing the 15mm for 10mm you have worsened you chances of getting them warm.


Have to balanced the system correctly........upstairs will need shutting right down , id start off with about 1/4 to 1/2 a turn on each lockshield upstairs. Is the pump set on a high enough speed?

 

[chrishutt]

For starters by replacing the 15mm for 10mm you have worsened you chances of getting them warm.

Sorry, but that's not so. 10mm is perfectly adequate for individual radiator branches.

 

[HarrogateGas]

I disagree............surely by reducing the internal diameter of supply pipework you reduce the flow to the rads???


He also indicates the boiler is an Ideal E type...........at least 25 years old. I would also suggest the system will have some degree of debris/sludge in thats more likey to block 10mm pipework.


10mm cannot be powerflushed wonderfully well either when a new boiler in the near future is required.

 

[chrishutt]

............surely by reducing the internal diameter of supply pipework you reduce the flow to the rads???

Following that logic, you'd use 22mm or 28mm for rad connections to minimise resistance. Yes, 10mm increases resistance compared to 15mm, but it's well within the capacity of the pump and so doesn't matter. In most cases even 8mm would be fine.

10mm isn't more likely to block since the water travels through the pipe at a higher velocity and so tends to scour itself clean. We all know that sludge collects where water speeds are slowest - radiators, boilers and oversized pipework.

As for power-flushing, I take your point. But I doubt if that is really significant.