Problem balancing cast iron rads after system powerflush

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Recently done a powerflush on a sealed system S plan with 12 cast iron rads and 6 steel rads. Also fitted a Magnaclean at the same time. Most of the pipework is 22mm with 15mm to the steel rads.
Prior to the powerflush, the system was reasonably well balanced to my knowledge but some of the rads not fully up to temperature due to sludge.

Now the powerflush has been done, I'm finding it hard to rebalance the system. All the rads are bled and there is no noise indicating air in the system. Of the rads working, the valves need barely a half turn on for them to be boiling hot. A couple though won't heat up despite valves being fully open.

The cast iron rads have the flow in at the top (wheelhead valve) and out at the bottom (Lockshield). Should I use the wheelhead to balance or the lockshield or both given that they are very sensitive to adjustment?
If using the lockshield (bottom valve), would the rad be more prone to sludging up quicker at the bottom since the flow is restricted at the bottom rather than the top?
 
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Use a differential thermometer to measure the temp change across the flow and return on each rad. Should be similar to the flow and return temp at the boiler. Usually twenty degrees for a condensing boiler and eleven for non condensing. The rads that don't work could be down to faulty valves, blocked pipework or radiator. Remove a non working rad and check that the valves and rad are clear. If you flushed with the boiler connected you may have blocked the boiler partially. If this is the Case the rads that don't work should be the end of the system. With heating flow is everything. Temp change can be measured and used to determine flow.
 
Recently done a powerflush on a sealed system S plan with 12 cast iron rads and 6 steel rads. Also fitted a Magnaclean at the same time. Most of the pipework is 22mm with 15mm to the steel rads.
Prior to the powerflush, the system was reasonably well balanced to my knowledge but some of the rads not fully up to temperature due to sludge.
Should have just removed those individually and cleaned out :idea: You`ve probably dislodged lumps of crud from the iron ones and they`re still lurking . Powerflushing is not a panacea :cry:
 
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Should you not be calling back whoever did the power flushing?

Tony
 
Should you not be calling back whoever did the power flushing?

Did you choose the cheapest nupty who did not know what they were doing?

Tony
 
You may have had an underlying issue before it was flushed (other than sludge) A pump problem maybe? As already said, you may have dislodged a large piece of magnetite that could be lodged in the impeller or somewhere else.

Cast iron rads with top to bottom pipework is screaming one pipe system, double check this as you could waste a lot of time on an issue you can't fix.

Sometimes people add rads to one pipe systems and pipe them up as two pipe which can cause problems like you describe.

Sounds like you may be a plumber so ask the customer about the history of the system, any changes etc...

Also, reconnect your flush machine and try it, see what happens.

Sorry if this is all repeat advice, or things you already know but this SHOULD be an easy one to fix assuming you've not missed anything obvious.

There's no moving parts except the pump and if it worked before it should work now, it's got to be something obviously / silly.

good luck!
 
I would imagine the steel rads wre added and they were piped as 2 pipe, the iron ones might still be one pipe
 

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