powerflushing very old mild steel system

[GQuigley67]

what are peoples thoughts on powerflushing an old open vented mild steel system with cast iron radiators? its in an office block with a commercial sized boiler.

 

[WHPES]

Have done it before but you won't shift all the muck out of the radiators though you will clear the pipework. Hard corrosion deposits inside the pipework cannot be shifted.

For the best results with the radiators the best way is to remove them and jet them outside.

Also remember that the larger the bore pipework the lesser effect a standard Kamco or similar machine will have due to lower dynamic pressure and flow velocities.

 

[GQuigley67]

well that is the problem, biggest pipework is at least 2" maybe 2 1/4" boiler is in basement, then you have ground floor, 1st floor, 2nd floor so I doubt a normal power flush would be able to cope.

 

[diamondgas]

It would take some magna to fill and restrict 2 1/4" bore pipe. If you're getting poor circulation I'd look more at the pump 1st, big magnet in there attracts detritis of the ferris kind .... Personally it's hard to guarantee the customer that it'd work especially when you arn't sure yourself. A lot of the older systems were 1 pipe design also which rules out flushing.. One rad at a time is most likely the approach?

 

[GQuigley67]

its not a 1 pipe sytsem its got a flow and return and the pump is on the return so it is under negative pressure, so there is usually a build up of air at the top floor and they are getting bad circulation to the top floor rads

 

[diamondgas]

It sounds like the circulation is slowing down somewhat, also what you say doesn't determine 1 pipe or 2 as both have the for mentioned flow and return at the boiler ... "Air!" can sometimes be nitrogen gas .... good trick to find out is to hold a cup upside down, let the 'air' out into it then but a source of ignition into the cup. If nitrogen you should hear a pop! It can also smell like cooking cabbage! Top floor rads collecting 'air' tends to point to ingress of air or bi-products of corrosion; Nitrogen! If the latter then a drain down and inhibit has some effect, if the former then a re-config of pipework may be needed... The heart of the system is always going to be the pump though. If 2 pipe, bye the way, has anything, recent or otherwise, been done to upset the balance?
Loads to consider ..... I'd still be pushed to wards the heart of the system, the pump. If that's slowing down then the extremities will be sacrificed! One way of looking at it ... lol

 

[WHPES]

I know its not a 1 pipe system but don't discount the benefit of flusing a 1 pipe system (with system cleaner) as this still gets rid of any debris in the pipework. Obviously the only way to clean the radiators in a 1 pipe system is to remove them and clean them out individually with a hosepipe outside.

 

[gaspastemania]

I know its not a 1 pipe system but don't discount the benefit of flusing a 1 pipe system (with system cleaner) as this still gets rid of any debris in the pipework. Obviously the only way to clean the radiators in a 1 pipe system is to remove them and clean them out individually with a hosepipe outside.

I cant imagine nobody would want to be lifting those cast radiators outside for a blast through with a hose then return them ,,,,,,,,BACK BREAKER!!!!

 

[diamondgas]

good money though !!! LOL

Imagine the blokes that carried them up to the top floor!

 

[WHPES]

I cant imagine nobody would want to be lifting those cast radiators outside for a blast through with a hose then return them ,,,,,,,,BACK BREAKER!!!!

Last time I did one of these sytems everything was on a ground floor and I hired a Genie lifter. Wouldn't bring them down from upstairs though!

If they were really fouled up I have some piano moving guys I use for getting large cast rads into awkward spots. They have lots of clever lifting and handling gear.

 

[diamondgas]

I know its not a 1 pipe system but don't discount the benefit of flusing a 1 pipe system (with system cleaner) as this still gets rid of any debris in the pipework. Obviously the only way to clean the radiators in a 1 pipe system is to remove them and clean them out individually with a hosepipe outside.

regards system cleaner WHPES. It's original design was to grasp hold of suspended solids within the circulating water, as far as I can remember. Unless you introduce an agressive chemical that does something to desolve the linings deposited on the internal walls flushing agents have a limited ability. Granted it was some years ago since I looked at the properties of flushing agents!

 

[gaspastemania]

lol well i'd be hoping the lift works !!

reading this post tho is the pump man enough in first place ?
just a thought as you state probs on top floor

 

[GQuigley67]

little more info for you guys

When I arrived on the job the old plumber had drained down the system and it was empty for a good while, he wasn't a good guy really he stole the sparks wire and didnt realise that everyone on the job knew each other, so he didnt return and he got what was coming to him and I took his place lol. I filled it up couple of months back with a couple of bottles of sludge remover, left the heating on for a week and returned to drain and then filled it up with some inhibitor. When doing this I also had to replace the old galvonised steel F&E with a new plastic one. Some rads and pipes are completely stone cold(top floor) I've tried a couple of times to balance the system maybe when I get my FGA with temperature clamps I'll be able to be a bit more accurate than just with my touch.

I have said to customer that the build up of air is probably nitrogen, and they are trying to bleed the rads with the pump running so its drawing in air instead of letting air out which isn't helping.

I had to drain a radiator recently to repair a corroded pipe, water was completely black

 

[GQuigley67]

lol well i'd be hoping the lift works !!

reading this post tho is the pump man enough in first place ?
just a thought as you state probs on top floor

lift works yes, I think I'm riping out a gd few of the rads in the summer as they have electrical heaters in each room with an electrical meter(rented rooms) Don't think they realise how messy it will be though !! They rads will not be easy to shift anyhow lol

 

[WHPES]

See if they will let you keep the rads - they are worth a lot of money on the architectural salvage market. I do a few up every year and good column rads sell for well over £200 refurbished plus I get the job of plumbing them in. I was paying £40 each to have them shot blasted and spray painted so that's up to £160 per rad profit for just a bit of lugging about.

 

[GQuigley67]

I'll put it in the contract then haha

 

[gaspastemania]

Sounds like it could be a half decent job?

 

[GQuigley67]

I hope so, right now they are penny pinching and doing my head in.

But...when the rooms are finished and fully refurbed, they will be renting them out to "clients" and making some money again and not caring about the money anymore !!

I advised them if they want radiators removed they'd be best doing it soon though in the summer and before rooms are fully refurbed as it can be messy

 

[diamondgas]

Stone cold is stone cold GQuigley67. Did they ever work? Have you inherited a problem that was already there to begin with? Loads of times customers have sworn blind that it's only happened "since I was there!" Bulls dodo!

Still down to circulation though with your problem, which, if you've given it a flush of sorts, points towards restricted flow which indicates poor circulation. Pump, ballance, air locks or blockages.... On a large system can be an absolute mare to find!!

 

[GQuigley67]

it is rather annoying, but the fact that it is a old system which was left drained for more than 2 weeks doesnt help either...

 

[diamondgas]

it is rather annoying, but the fact that it is a old system which was left drained for more than 2 weeks doesnt help either...

Just a thought *ping*

The floor in question wouldn't happen to have a zone valve stuck closed, could it? Like are all the rads off totally?

 

[GQuigley67]

there are no zone valves as far as I'm aware, I have had them hot before but they eventually go cold and have alot of air in them.

 

[diamondgas]

Air can be a nightmare to get shot of! You would think after a while though it would have dispersed! The pump wouldn't be drawing air in somehow is it? With all the black water you're talking about and the sluggish circulation you could have some major blockages to contend with. Doesn't sound like there's any easy solution GQuigley67. Circulation differential temps F&R will indicate how well the water is flowing through and around the system. That would pobably be my next step...

Good luck!

You could always give your client a quote for replacement!

 

[FD Powerflow]

No offence lads but youve got your chemistry wrong, Nitrogen is not produced as a byproduct of corrosion for starters where would it come from there is nothing in a central heating system containing Nitrogen its a fertiliser!

When you get electrolytic corrosion in a central heating system Oxygen is removed from water and binds with Iron for example forming Iron Oxide, FeO3 or similar FeO4 is magnetite the black sludge whereas FeO3 is red sludge. And what do you get if you remove Oxygen from water.....

H20 minus O = H2 which is Hydrogen, and Hydrogen gas can be lit with a match in the way in which Diamond Gas describes.

Also no sludge removing chemical cleaners "desolve" sludge, the only thing even an acidic cleaner would dissolve is limescale, which from the symptoms could be in the system but more than likely its just a oxygen issue which is allowing fast corrosion of the mild steel.

Treatment methodology from experience is as such on commercial jobs:

1) Powerflushing wont work, as Diamond quite rightly says no machine would have the right flow rate/pressure on a pipe diameter of that size.
2) The pump is the heart of the system and if you can, get Grundfos on the phone to tell you what pump should be in place, it might be worth a new motor and the benefits are two fold, firstly the new impeller will probably have a nylon propeller meaning sludge wont be as attracted to it, and secondly the new alpha range can almost halve the electric running costs for a standard pump.
3) Add a suitable dispersant cleaner such as Fernox F3 or Sentinel X400, you need to size the system up against the KW output of the boiler to work out how much of this you will need, a rule of thumb is 12 litres of water in the system per 1kw of heat output so;

45KW Ideal Concorde for example would equate to 540 litres of water in the system in which case you need 6 bottles of F3 or 8 bottles of X400, trust me have almost taken one rep to court over dosage levels before they came back with a peace offering of product after a customer went legal on me.

4) Get hold of either a 28mm TF1 or 28mm Magnaclean and get it somewhere on the return, if this run doesnt get any smaller than the sizes you mentioned however you may need to step up to a magnaclean commercial which are around £2000 and are a right pig to clean. Im a Fernox fan as Ive said before and the reason for this is you can clean the TF1 in about 30 seconds without even getting your hands wet (plus the valves seal properly unlike some others Ive used).

5) Use the filter to dose your F3 and run the system up to temperature for at least 4 hours, once this is up go and empty the tf1, and rinse and repeat. What you need is for the filter to start looking clear, this genuinely in some cases has taken weeks on a few jobs of mine, to the point where I have fitted more than 3 filters at one job in a football stadium. If one or two rads are the worst culprits then the best thing to do is whilst the system is running close off all trvs and ls' to every rad but the worst offenders and give them 30 mins a piece and watch what goes into the filters. Once the filters start looking clean you can look to drain down the cleaner and water.

6) At this point you need to add a good level of inhibitor, again I prefer Fernox although I have used Sentinel before and both of which will protect the system provided they are dosed correctly, in the system size were proposing its the same amount of bottles again as X100 despite being in a bigger bottle actually only protects 69.95 litres of water whereas F1 protects 100. I would then get a system check kit and send it off to the lab which will show that you have done your job properly, not only to give the customer peace of mind but also to prevent you from getting it in the neck if theres a major installation error which is whats letting in the extra Oxygen as this would weaken the Inhibitor concentration.

Apart from that if you get stuck with anything PM me or post it on here.

Best regards

 

[diamondgas]

Hey thanks for the chemistry lesson, I knew it was a gas thet ended in a '...gen' ... lol