Cleaning large heating system

[oz-plumber]

Hi Fellas,

Have a larger job that's starting to have flow problems.

The system as 2 - 250 kw boilers servicing probably 300+rads.

The system was installed @ 15 years ago and stated previously starting to have flow problems to sections of the building, particularly the radiators at the end of the mains - furthest run from boiler / pumps.

This year the problems have really shown up and are stating to cause quite significant issues due to inadequate heating of the facility.

What would be the best options for cleaning the system?

There are 65mm in-line filter / strainers at the boilers, which are cleaned on a regular basis, but now don't seem to improve the systems performance.

There also seems to be flow problems caused by air locks at random radiators.

The water bled off from the panels is a black as the ace of spades.
Bleeding the air out requires connecting hose to plug and draining water from piping until constant flow of water.

Some panels have noticeable cold spots - sludge.
Would it just be best to replace those radiators and keep replacing effected radiators or try and clean the entire system

Any feasible suggestions on what's best.

 

[joni os]

If all radiators installed at same time and some are corroded then most will be same.
Assuming client will not pay for 300 plus new rads. I would remove 30 at a time, thoroughly
flush with plenty of plastic hammer, inspect for serviceability and reinstall or replace as necessary. As work progresses the extent of problem will become apparent.

 

[ShaunCorbs]

is the system done out of iron ?

 

[Best]

That's a seriously big system!
I know you said there are filters at boilers, but just wondering is it also possible that pumps are impaired due to build up magnetic scale? I see that on domestic pumps.

 

[joni os]

Agree above, have removed pumps with impellor so clogged it might as well been a flat rotating disc.

 

[Best]

Agree above, have removed pumps with impellor so clogged it might as well been a flat rotating disc.

Exactly! And that just ruins the pumps performance and the furthest few rads heat very little.
Pumps are, as we know a big electro magnet when their motor is on and act like a filter of the black remains of metal.

 

[AWheating]

how is the system sectioned off? is it possible to powerflush a section at a time? what flushing pumps are available to your market?

the inhibitor cost will be huge on refill.

 

[AWheating]

also a thermal image camera will prob help you alot.

 

[lame plumber]

be worth doing a thermal survey of every rad, ascertain if all or just some need cleaning and if its one or two or all circuits affected and take it from there.

 

[Ermintrude]

The pH and water oxygen levels probably through the roof.

System should have active water control and a scavenger.

Drop rads out and use a rems type cleaner on the mains and risers. - the flow in a dirty main is laminar and usually u get deposits building in areas of high friction.

Is it piped up properly? No tees off the bottom of mains etc?

One pipe system? Have u checked the pumps? The seat can become what appears to be carbonised but it's actually very compacted magnetite.

It's not open vent is it? Balancing valves haven't failed or become blocked?

If you know what's in your system u can mix the correct chemicals and burn it clean

 

[oz-plumber]

The pump impellers seem fine, pulled one apart recently to check.

The system is a 2 pipe sealed system and the piping is all copper.

There just seems to be a lot of air in the system that has to be flushed out by connecting a hose to a plug on the rad and flushing up to 20lts of water through until a steady flow of water is coming out. Sometimes the air is on the flow and other times on the return line.
This exercise has probably been done to 30 rads around the building

The system has been installed quite well, except for bleed off lines / air vents in the ceiling void.
The piping is an overhead system with drops to each radiator.

 

[Ermintrude]

Remove the Avv at high level they 70% sucking on air .

Fit a decent air separator at the boiler like the spirovent

http://www.spirotech.co.uk/en/products/deaerators/

Acid wash the systems **** off and then monitor water quality. If it's still changing after 20 days u getting air ingress

 

[joni os]

If it wasn't a sealed system I would say 100% it's sucking air. Look into maintenance record.
Have pumps been running when pressure was down. On such a large system in a commercial setting , adding pressure to system is a necessary quick fix, leaving the problems for you to cure.

 

[newcastle phill]

I think id walk away from that lol.
Gonna be a total PIA

 

[Ermintrude]

It a challenge

 

[FD Powerflow]

Not being daft but get on the phone to your local Fernox or Sentinel rep, they'd probably love to get a case study like that, probably give you some stuff to use too. We did a job in 2008 back on a school that had been converted into offices with a 240kw remeha biomass. The rads were so full of sludge they had replaced two grundfos pump sets at over £1.5k a piece! I got plumb center to ring the Fernox rep and she came out and took a water sample, about a week later she rang and explained to the client what was wrong and what needed doing. Client was happy, we did the work, used a new cleaner from them (which was free), and then dosed with inhibitor, took another sample to check and it all came back great. Would also agree with Ermintrude that in most cases air is the problem so get a deaerator fitted, Spirotech make the plumb center own brand called JET and we fitted a 4" combined dirt and air on at the same time as the dosing pot.