underfloor heating problems

[taxes]

Hi
Looking at your manifold photo again there appears to be something missing.The end of each manifold chamber should be connected to something, either the flow or return pipe from the heating source via isolation valves or an automatic air bleed valve - or were there no isolation valves and you disconnected the heat source and put in blanks while you flushed the system?

 

[suts89]

No the flow and return are at the left hand side which cannot be seen in the photo.

Each has an isolation valve which I was able to close.

I'll try and posts picture of the overall schematic later.

Cheers

 

[taxes]

Hi,


OK, so where are the automatic air bleed valves? They should be on the opposite sides of the manifolds from the input/return i.e. to the right of your flushing connections in your photo.

 

[flowboy]

Resurrecting an old thread but have to say; taxes replies are spot on. Thanks for your clear advice.
I don't know if suts89 tried to dismantle & clean the flow gauges? I am flushing my system at the mo' & was wondering if they came apart.

Regarding this particular Nu-heat system, which appears to be the same type as ours, there are no automatic air bleed valves on the manifold. There is a std radiator manual bleed valve on the flow bar. Some other makes no doubt have auto bleeds on them. I read the latest Nu-heat (brass) manifolds have isolator valves to enable the gauges to be removed for cleaning without de-pressuring.
Our system - 3 years old - has been great, no probs, but has the same deposits on the glass of the flow gauges making them unreadable. I am certain it is rust. Our CH system includes radiators (some 1930's cast iron ones also) so there is a lot more potential for rust / sludge than in a UFH only system. It had screwfix inhibitor in it. I would be very surprised to see so much deposit in a plastic/ally/brass UFH only system.
I have just installed a Fernox Tf1 filter & there was a lot of c**p in it when I first cleaned it! This suggests insufficient qty of inhibitor in system. I cannot stress enough the need for a filter in your CH. particularly in a UFH / steel rad mix like ours. UFH suppliers should make a point of recommending it in mixed systems. Before our UFH, the previous boiler (BG installed) packed up at 5 years! - due to the amount of c**p. The entire ancient pipework was steel. All gone now. A £100 filter would have saved a lot of expense...
I also read elsewhere that people had problems with split & bursting UFH pipes - in slabs! - some of it will be bad install's, some poor or now obsolete materials - . Plastic pipe systems are vulnerable to excessive heat. UFH systems are not designed for radiator temperature water through them. You should have a cold feed & use a mixer valve on the flow to manifold if you have rads. Failing that, turn your boiler down! I read that condensers work better at lower temps.

 

[Agile]

I always wonder why DIYers like to buy cheap chemicals rather than the proper professional ones like the Sentinel X100 for example.

Tony

 

[taxes]

Hi Flowboy

Thank you kind sir. I've made a note on my CV should come in useful some time (I've just had my 78th birthday!!)

A couple of points.

I covered the way to remove the flowmeter glasses but just screw down each meter using a spanner carefully on the nut and then unscrew the glass part by hand. Use a coarse rag to help grip it.

Even if isolator valves are used you still need to release the pressure before removing the flow valve entirely (as distinct from the meter glass).

Inhibitors don't prevent all muck. They certainly slow down rust etc. but two other factors are the presence of air in the radiators. If you are having to top up the system often that will encourage rust production. In older systems steel and copper pipes/fittings were often found in the same system which would result in electrolytic action (creating the equivalent of a huge 1.5 volt battery) and the corrosion associated therewith.

 

[flowboy]

I always wonder why DIYers like to buy cheap chemicals rather than the proper professional ones like the Sentinel X100 for example.

Tony

Indeed! But when we buy our Basic Baked Beans from T*sco the cans do actually contain beans & sauce. Just that when you need a good feed, half a can doesn't do it.

Taxes, congrats on the birthday. I got the bit about unscrewing, did wonder if you had originally meant "don't" use a spanner - owing to the risk of excessive force / slipping = broken glass!
The Nu-heat statement (2010) does say "without releasing pressure" but as you say even with the isolators the water will still be at pressure. There just won't be so much of it! There is no mention in Nu-heat tech about removing glass, only unscrewing entire unit, using as you say a spanner. There are o-rings in there that manufacturer will no doubt say should be replaced if meter removed. They do recognise that staining of meter glass is an issue. I guess at about a tenner each the meters are not too pricey to replace if needed.
Hardly ever had to vent rads at all here. You should have seen the old system tho - pretty certain it hadn't been checked in the 5 years or so since the boiler was replaced. The rad in one room was 1/2 full of silt.

 

[Agile]

Indeed! But when we buy our Basic Baked Beans from T*sco the cans do actually contain beans & sauce. Just that when you need a good feed, half a can doesn't do it.

You can see and taste the cheap baked beans!

But when you buy a can of "Patel's Super Duper Inhibitor", you have no idea of what is in it and what, if anything, it might be doing for you!

 

[Onetap]

Inhibitors don't prevent all muck. They certainly slow down rust etc. but two other factors are the presence of air in the radiators. If you are having to top up the system often that will encourage rust production. In older systems steel and copper pipes/fittings were often found in the same system which would result in electrolytic action (creating the equivalent of a huge 1.5 volt battery) and the corrosion associated therewith.

Different metals are almost unavoidable in a heating system, typically steel and copper. That can cause electrolytic action, but it shouldn't. The one other thing that is needed, to make the system into a big galvanic corrosion cell is a suitable electrolyte, preferably acidic.

Where do the acid compounds come from, then? Active soldering fluxes, mostly.

Maybe Mr Taxes can recall when active, self-cleaning fluxes came into use and could tell us whether he recalls problems with black sludge (corrosion products) in heating systems prior to that.

French plumbers do not soft solder joints, they braze them; there are no acid flux residues to get into the heating system.

Some French language boiler manuals say not to use corrosion inhibitors in the heating system; these are the same boilers you lot are fitting.

There is NO power flushing industry in France. There is virtually no black sludge.

 

[suts89]

Been meaning to post an update for months now.

Anyway to cut a long story short, the flow meters in question are not designed to be completely dismantled for cleaning.
New flow meters were purchased and installed. With the new meters installed i was able to set up and balance the system properly which appears to have done the trick.
The new flow meters however are now discoloured and most likely clogged again!
Thanks for all the input.

 

[Norcon]

You just can't beat brazed copper joints. You do get a slight carbon residue inside the pipe after the process is carried out.

In a refrigeration system that's not acceptable thus oxygen free nitrogen is purged through the tubes as the brazing process is carried out.

But I wonder what rental charge they pay in France for the gas bottles.
Here Oxygen size F is £86 per year and dissolved Acetylene size M is also £86 per year.

 

[Agile]

But dont even the French use flux coated brazing sticks or a flux paste?

I will have to see what is on the shelves the next time I am in Brico Depot!

Tony

 

[Norcon]

No need for any flux.

 

[Agile]

Only I suspect with flux cored sticks or those with phosphorus content!

Or an inert gas environment!

Tony

 

[flowboy]

Well I stripped my gauges down and they cleaned up a bit but really replacement is the only option & as I said, put a filter in as well.

With all this phosphorus stuff etc e're getting off the thread here but... Re. brazing v's soft solder, I read somewhere that in some solar installs' the system can reputedly get hot enough to soften the solder = loose joints. Brazing is recommended in those cases.
I am intrigued in the "no black sludge in France" & the common use of copper brazing there. Is that your actual experience?
Acid flux is likely a major contributor to bad corrosion in our systems; we are supposed to flush it all out before commissioning & not blather it on excessively to start with!