Improving a microbore system

[MrDuck]

I am refurbishing a small 1980s house which has had 8mm microbore heating installed. I would like to bring the installation up to a good standard but need some guidance from those more experienced with such systems. First, some background:
- The old cast iron boiler has been replaced by a Vaillent ecotec 415
- I have replaced all the old radiators by compact style ones with Danfoss TRVs (except the rad closest to the thermostat)
- I am shortly to replace the existing gate valve bypass by an automatic type
- There is clearly sludge in the system as I am getting blockages to the radiators at the front of the house. I have overcome these so far by back flushing with mains cold water via the drain valve on the lounge radiator but I think its quite marginal as to whether it recurs.

I would like to reduce the sludging/blockage problem and am considering the following but don't know which is going to be best:

- Fitting the pump back to front and trying to pull sludge back from the blocked manifolds (danger it all ends up in the boiler?)

- Using Fernox F3 or similar to clean the system (is it really effective?)

- Fitting a Magnabooster (or equivalent). It's almost impossible for me to fit this in the return to the boiler without blocking access to the boiler, but I could fit it just before the pump in the flow pipework. As I am most concerned about muck entering the 8mm microbore flow pipes this strikes me as the best option. Comments please??

I would really appreciate any advice on how to proceed. I obviously don't want to make things worse and have read elsewhere that power flushing a microbore system is a really bad idea so am not considering this.

 

[Agile]

It is not a bad idea to power flush a microbore system.

Its just that it does not usually work very well.

Particularly if double entry valve have been used.

To improve it you would need to repipe in 15 mm or at least 10 mm and with two valves per rad.

Tony

 

[Agile]

But if it can be cleaned and a mag filter fitted and properly chemically dosed then it should stay clean.

Tony

 

[newbuildinstaller]

Power flushing will do nothing!!!

It relies on the flow of water to wash the dirt etc away through the pipes. Now imagine what kind of a flow you would achieve firing a 8mm pipe into a 1/2" hole (rad tail)

All you may achieve would be causing leaks/blockages

BEST THING TO DO

Add F3 to system

Then after a few days

Remove each rad and empty out side and flush out with a hose pipe.

Open each rad valve into a bucket while the filling loop is open (you may need a hand to be in two places at once)

Refill system and add inhibitor and maybe a MagnaClean (although if your system is now clean and your rads are new and full of inhibitor it isnt that important)

 

[MrDuck]

Many thanks for the guidance everyone. The rads have got valves at both ends and there are drain-down lockshields on the three downstairs rads so cleaning with F3 and draining each one down to get the sludge out would be easy.
It seems to me that with the low flow rates of microbore circulating sludge is just going to settle in the bottom of the rads so a Magnaclean or whatever is not going to do that much extra. But the BG man recommended one when he serviced the boiler so maybe I have to fit one...

 

[gas112]

Take the rads off flush them out in the garden then add x400 for a couple of weeks and flush again or x800 for a day or so.
Microbore can be a pain at times and even after doing this you may have to cut manifolds out and rod and flush them through even though they look clear a lot of crude sticks to side

 

[Agile]

Power flushing will do nothing!!!

Add F3 to system

Why would you use F3 rather than F5 ?

 

[MrDuck]

Thanks for the updates everyone. An amusing cautionary tale to finish with:
Having changed all the radiators in my house I took them to my local recycling tip for disposal. Once there I put my builders gloves on to make sure I didn't cut myself on any sharp edges and then proceeded to throw the old rads into the metal recycling container - great fun!
All went well until the last rad. By chance an exposed valve spindle on the last rad caught in the cuff of one of my gloves and as I threw the rad into the bin I was pulled in after it...and ended up balancing by the waist over the parapet! Fortunately the bin was nearly full so that is where the story ends, and I was (by good fortune) unhurt, although very shaken.
You can't wear enough PPE can you...

 

[Richardthe3rd]

Thanks for the updates everyone. An amusing cautionary tale to finish with:
Having changed all the radiators in my house I took them to my local recycling tip for disposal. Once there I put my builders gloves on to make sure I didn't cut myself on any sharp edges and then proceeded to throw the old rads into the metal recycling container - great fun!
All went well until the last rad. By chance an exposed valve spindle on the last rad caught in the cuff of one of my gloves and as I threw the rad into the bin I was pulled in after it...and ended up balancing by the waist over the parapet! Fortunately the bin was nearly full so that is where the story ends, and I was (by good fortune) unhurt, although very shaken.
You can't wear enough PPE can you...

LOL!! Yes, it's one of these situations where you hope no one has seen you & you feel a bit of a fool. Been there 100 times.

8mm can be a swine for blocking at the manifolds, but on the positive side there's less water in the pipes, so a bit easier to clean out. A cold mains flush can work wonders, but I'd be fearful of your new boiler & ensure it's protected. You're correct, lots of crud will stay at the bottom of the radiators, so flushing them often will help.

With a new boiler & radiators, that only leaves the pipe work, so there's a good chance you've removed a lot of the crud already. Is there any circulation problems with any radiators?

 

[D_Hailsham]

It seems to me that with the low flow rates of microbore circulating sludge is just going to settle in the bottom of the rads

Flow rate (litres/sec) depends on the size of rad (kW) and the temperature differential. What does change is the velocity of the water (metres/sec), which increases as the pipe diameter decreases.

Sludge is more likely to settle if the velocity is low, so sludge is less likely to settle in microbore pipe! (Sit back and wait for the flack )

 

[Richardthe3rd]

It seems to me that with the low flow rates of microbore circulating sludge is just going to settle in the bottom of the rads

Flow rate (litres/sec) depends on the size of rad (kW) and the temperature differential. What does change is the velocity of the water (metres/sec), which increases as the pipe diameter decreases.

Sludge is more likely to settle if the velocity is low, so sludge is less likely to settle in microbore pipe! (Sit back and wait for the flack )

Very true DH, however, the tight bends that are found at the manifolds can be blocked solid. If that's the case, then clearly there would be little or no circulation & the radiators/radiator would just not heat up.

 

[D_Hailsham]

Very true DH, however, the tight bends that are found at the manifolds can be blocked solid.

I assume you mean bends outside the manifold, in which case that is poor installation.

 

[Richardthe3rd]

Very true DH, however, the tight bends that are found at the manifolds can be blocked solid.

I assume you mean bends outside the manifold, in which case that is poor installation.

Well with respect DH, if you can install something like this between two joists without a few bends on the 10mm pipe, you're a better man than me.
http://pegleryorkshire.stage-server...2bc0&Rid=b6c86f52-4b21-4667-ac51-f3878ea68e0c

 

[MrDuck]

Richardthe3rd - Yes I do get blockages, mainly to the main lounge radiator (which is actually oversized for an 8mm feed anyway). These seem to occur after draining down and refilling and have been fixed each time so far by back flushing with mains cold water from the drain valve on the lounge radiator. So I suspect sludging in the feed manifold (wherever that is!).

I agree with D_Hailsham that the 8mm pipework itself should not block (although it has 90 degree elbows in where it pops out of the wall to feed the downstairs rads) as the flow rate is high (the valves to the lounge rad are fully open). But once the water enters a big rad it will slow down a lot and deposits may well drop (which seems to me to be better than going back to the boiler).

Ideally I would like to get the crud out of the manifolds which is why I have suggested a reversed pump, treatment with Fernox or equivalent, and/or a filter (but access to the boiler return is very difficult which is why I have proposed putting a filter before the pump).

 

[D_Hailsham]

Well with respect DH, if you can install something like this between two joists without a few bends on the 10mm pipe, you're a better man than me.
http://pegleryorkshire.stage-server...=b6c86f52-4b21-4667-ac51-f3878ea68e0c[/QUOTE]