Power FLush unsuccesful

[Bunker]

This morning I started my first power flush. 13 rad house, some downstairs rads have huge cold spots in the middle - in fact easier to say they had small warm spots on the ends. The 2 main culprits are an 1800x500 double rad and a 2250x500 double.
Its a Sentinel Flush4 machine and am using Sentinel X800. Followed the MI but despite LOADS of gunk coming out, the cold spot on the bigger rad hardly budged. I was there for 3 1/2 hours pretty much just on those 2 rads (including initial set up, wash out etc). I tried slapping the rads with a length of wood and palm banging them. Im going back on wednesday so will take a rubber mallet too. Ive hired the machine for a week and got some more work done this alvo so I havnt lost out much. I threw in another tub of de-sludger I had in the van and restored the system, hoping it will work its magic over the next 48hrs.

Anyone any advice beyond this?

Many thanks

 

[villa_tom]

I've only ever had this once and we had to replace the rad, we flushed it for ages, had it off the wall and flushed it manually and it was still the same.

 

[Sid Viscous]

I've seen a neat little mangnetic roller for agitating the gunk in rads on Corgi website. Never used one though, not had the pleasure of a powerflush yet

 

[CXR100]

armegh (i think) do a drill bit to fit a sds to shake the rads! never used one! knowming my luck everything would jest start leaking!

 

[tamz]

Long radiators need a good flow rate. Check the valves are not sticking. What size pipes? Have they ever worked?

Take them off and you will probably find they are relatively clean but a 7½ft radiator is a bit of a humpf on your own.

 

[Roger Welton]

Vibrahammer (sds drill attachment) seems quite effective at shifting stubborn muck from rads (and fluff from behind!) is quite noisy though

 

[md68]

I've a rad hammer that goes on an SDS drill and it works really well. Just make sure to put a cloth over the end so you don't damage the rad.

 

[tamz]

VibraClean - Adey VibraClean

expensive for what they are but useful.
I don't think the rads are your problem here. There is insufficient water flow.

 

[Bunker]

The magnet roller is by Fernox and I bought one but its no good on these blighters.
Rad valves are new and pipes are 15mm. I didn't ask if they worked before good point.

 

[tamz]

Check the flow going through it with everything else shut down before you add you chemicals by dumping through it and watching the dump hose.

 

[FD Powerflow]

Probably the Sentinel machine mate, only lets you go to 40 degrees, get yourself a Kamco or Fernox machine hired, you can run the boiler at full temp, this lets the cleaner ping around more and indeed faster. You've done the best thing in leaving the cleaner in and letting the system run for a few days, this will loosen the sludge up and then your machine will come into its own.

 

[vern]

Probably the Sentinel machine mate, only lets you go to 40 degrees, get yourself a Kamco or Fernox machine hired, you can run the boiler at full temp, this lets the cleaner ping around more and indeed faster. You've done the best thing in leaving the cleaner in and letting the system run for a few days, this will loosen the sludge up and then your machine will come into its own.

What he said or Proflush machine

 

[Bunker]

Thanks all, Im back there tomorrow also armed with a £50 5litre can of:

Deposit Remover | Liquids | Central Heating | Sentinel central heating products.

and a new toy - the vibra hammer.

If that dont sort it Ill replace the bar steward.

Thanks again for all your help so far

 

[SJB6]

Hi.

Just a little insight.

When I power flushed the job was always atleast a day, maybe two if a large system.
First i would flush the system as one, then just the boiler and then each rad on their own in turn and then flush it all as one again at the end.
Like some have said a good flow rate is required but another thing you should consider is that sludge remover will only break sludge down, in order to stop the sludge binding again a silt free agent must be used, it's pointless breaking sludge down only if it's going to bind again before being flushed out.
If flushing doesn't rectify the problem then replace the rad or rads suffering, less time and probably cheaper, certainly in the long run.
I was called to a system once that had been flushed a few times but the system was so bad I had to install a complete new system. The old 22mm pipe had an internal bore of no more than 2-3mm, the sludge was that bad.

 

[Sid Viscous]

And this is why microbore should be illegal IMHO

 

[tamz]

Think of big long radiators like a pond with a small river running in and out at both sides.
The water flowing in and out may be running fast but the pond can be quite still with no apparent movement. The flow through the pond is the same as entering it but it slows down so much you can't see it
Now think of your long radiator and what the water is doing inside.
It flows in fast then because of the volume of water, it slows right down, the thermal currents take over and the hot water starts rising. If the radiator is long enough the middle section will never get enough hot water to heat properly unless you have a big enough flow rate to get the water far enough across the radiator before the thermals take over.
Trv's don't help (have a look inside one)

 

[Bunker]

Thanks tamz, always useful to get a different perspective on things.

 

[R1CKY]

Drain the radiator to half its volume. Water will flow to the path of least resistance, draining some of the water out of the rad will remove the easy path and force it to try and move through the sludge. Keep changing the pump direction too, this will agitate the sludge and eventually break it down.

Where have you connected the powerflush to?

 

[Bunker]

Unit attached to pump valves. Thanks

 

[smtplumbing]

bunker i had had the same problems before connect the power flusher to each end of the rad and clean it that way you should be ok after this

Steven

 

[Sid Viscous]

Like the pond analagy Tamz, but what would be your prescription? More smaller rads, upsize pipe work, booster pump?

 

[tamz]

Big long rads are always a problem. Sludge gets the blame but seldom is the only cause of it. Most times they have been like that since the day they were fitted but years ago no one bothered too much. They were just glad to get some heat after being used to scrapping the ice off the inside of the windows on a cold night.
You need the flow rate. On an open system you can't just turn up the pump as this may create more problems than it solves. On a sealed system it may mean a lot of balancing.
Keep pipe runs short, balance the system well and look at what trvs's are used as some are very restrictive.
If that won't do it then 2 rads instead of 1.

 

[jtsplumbing]

I do not use sentinel products, never got on with them ! allways use Fernox or Kemco for best results.

 

[dancinplumba]

I do not use sentinel products, never got on with them ! allways use Fernox or Kemco for best results.

How do you not get on with a liquid ??

 

[Bunker]

UPDATE: Spent most of the day there today and found that generally the machine was pretty good although Im relieved to hear that other makes will run at boiler temp - 40 degrees is a bit pointless. The offending 3 rads are coming out, I told them they need changing as even with my mighty new vibrahammer, nothing shifted. Taking on the point of flow mentioned before, I have several times run the machine only on each rad singularly but even with that concentration, nothing changed. So 3 new rads (2250x450 dbl, 1800x600 dbl, 1200x750 sngl) added to the bill....
The flush was worth it though, the muck coming out was outrageous. I also followed the advice above of dropping in a magna cleanse magnet on a string - that bulked out very quickly and I was drawing that off every half hour or so.
Ill pu up on the price checker part of the Arms about the Sentinel.
Thanks again chaps

 

[kay-jay]

You did remember to open the lockshields up fully?.....

 

[Heating-eng]

I use the fernox Powerflush machine and filter and it works really well on big systems and at high temp.

also x800 is very good

 

[Bronze_tap]

Did you flush EVERY RADIATOR FEED/RETURN PIPE, until the clear water came out?
See my reply to your's and other similar flushing problems...

 

[Howsie]

Did you flush EVERY RADIATOR FEED/RETURN PIPE, until the clear water came out?
See my reply to your's and other similar flushing problems...

But you didn't do a power flush. You rinsed the rads and some of the pipe work. Big difference.

 

[Bunker]

But you didn't do a power flush. You rinsed the rads and some of the pipe work. Big difference.

Not sure what you guys are referring to, I certainly did a thorough power flush and yes, all ls open on overall wash otherwise all flushed individually forwards and backwards erc

 

[Howsie]

Not you mate, that bronze tap chap.

 

[Bunker]

Ok.
3 new rads fitted and lovely n hot. Top tip tho: always have rad tail extensions on board!!