42 year old open vented system on microbore

[rick]

Hi everyone,

I'm a new member and not a plumber or central heating engineer.

Mum and me live in a 1970 house she's had from new and the installed central heating is very primitive (no thermostats except the one close to the Concorde boiler, no zonal valves). As far as I know, it's never been cleaned. On the Concorde, the electronic ignition gave up long ago, but apart from that everything works fine. All radiators are hot, there's no leaks and none ever need to be vented. It's even got some ground floor underheating due to the presence of the microbore pipe runs! Maybe it's living on borrowed time? (there is a fair bit of kettling!)

Either way, looking to have a groundfloor extension made, so that Mum can live downstairs. Extra rooms needed for bedroom, downstairs bathroom etc. Therefore, will need to add extra heating and will look at the very least to change the boiler to go along with the extra piping and radiators. How further does everyone thing I should go? As it's microbore, should the whole system be replaced? Or, should the system be cleaned and flushed, radiator by radiator; then pressure clean the system as a whole; then change the boiler; then add the new piping and upgrade with thermostats? I've had a few opinions from both builders and plumbers. One suggested keeping the piping and changing the rest, the others to change the whole system. A major disruption to change the piping:- either buried in the solid ground floor or twisting everywhere under the upstairs floorboards. Your opinions all gratefully accepted!

RicK

 

[SimonG]

Disconnect boiler, cap open vent and cold feed and test whole system. Sealed system prv will blow off at 3 bar, based on safe leeway I'd go to 4.5 bar and see if you get any drop.

 

[rick]

Thanks, a bit over my head, but will relay that to the plumber. I assume if the system handles the pressure it is Ok to go for a pressured new system with the old pipework?. If there's problems I suppose I'll have to get a complete new system.

If the old system does handle the pressure then I was thinking to go for a veissmann 222 / vailliant 937; getting rid of the cylinder and old radiators but keeping the microbore and pipework largely as it stands. Will there be any old sludge in the pipes to get rid of? Would the new system somehow flushed to get rid of sludge prior to the boiler being started?

 

[fast phil]

yes there will be plenty of crud laying in the pipe work so a power flush before the new boiler gets installed is a must and i would all so fit a tf1 filter on the system hope this helps

 

[rick]

Cheers Phil. I think it's all getting alot clearer now!

I'll look to get old system pressure tested at simonG suggested. If all OK then get rid of old boiler, cylinder and rads. Then new rads and TRVs fitted onto the old microbore. Then as you suggest, power flush and have new filters put on. Then have installed new combi boiler with it's own local hot water reservoir for fast hot water response....

Does that all sound something like how to have it done???....

If the microbore goes kaput, then or in the future, I suppose the floor boards go up and the pipe drops have to go in!

 

[Mike Jackson]

You could always look at fitting an intergas. These can be used as open vent combis.

 

[fast phil]

I think micro bore pipe gets abused a lot as it can be bent at too tighter angles which causes poor flow and could lead to blockages if i was you i would re pipe it as it is a old system this will give your new boiler a good start in life and a intergas boiler would be a good boiler for the job

 

[rick]

Thanks, is your suggestion to fit an open vented Compact HRE OV to keep the central heating still open vented but to go for pressured hot water?

 

[rick]

I'm hoping that it is OK if it pressure tests Ok? The idea is to suck and see; if it doesn't perform I'll have to get the piping changed as well. The old system works well now with a wilo gold 50 pump on setting 2 ..?..

 

[rick]

Ah Mike, I've looked again at the intergas web-site. Is the idea to use the Intergas Combi HRE because it has two heat exchangers. The heating one to be converted to open vented operation somehow?

 

[dancinplumba]

Ah Mike, I've looked again at the intergas web-site. Is the idea to use the Intergas Combi HRE because it has two heat exchangers. The heating one to be converted to open vented operation somehow?

yes

 

[Mike Jackson]

Ah Mike, I've looked again at the intergas web-site. Is the idea to use the Intergas Combi HRE because it has two heat exchangers. The heating one to be converted to open vented operation somehow?

The intergas combi comes as standard without the pressure vessel etc. to be used as a sealed system. These have to be bought as a separate kit but if you don't use them the combi will work as an open vented combi. There may be a need to combine the feed and vent to prevent air ingress. If you were to repipe at a later date the system could easily be converted to a sealed system.

The Intergas comes as standard with a 3 year warranty but if you use an Intergas Platinum 5 installer you will get 5 year warranty.

 

[rick]

The intergas combi comes as standard without the pressure vessel etc. to be used as a sealed system. These have to be bought as a separate kit but if you don't use them the combi will work as an open vented combi. There may be a need to combine the feed and vent to prevent air ingress. If you were to repipe at a later date the system could easily be converted to a sealed system.

The Intergas comes as standard with a 3 year warranty but if you use an Intergas Platinum 5 installer you will get 5 year warranty.

Thankyou Mike, I'll pass on the info/recommendation to the prospective plumber doing the job and check the installers in my area.

 

[Centralheatking]

If you are near West Lancashire i will come out at no cost and tell you what I think you should do - your question and explaination touched me

cenrralheatking

Hi everyone,

I'm a new member and not a plumber or central heating engineer.

Mum and me live in a 1970 house she's had from new and the installed central heating is very primitive (no thermostats except the one close to the Concorde boiler, no zonal valves). As far as I know, it's never been cleaned. On the Concorde, the electronic ignition gave up long ago, but apart from that everything works fine. All radiators are hot, there's no leaks and none ever need to be vented. It's even got some ground floor underheating due to the presence of the microbore pipe runs! Maybe it's living on borrowed time? (there is a fair bit of kettling!)

Either way, looking to have a groundfloor extension made, so that Mum can live downstairs. Extra rooms needed for bedroom, downstairs bathroom etc. Therefore, will need to add extra heating and will look at the very least to change the boiler to go along with the extra piping and radiators. How further does everyone thing I should go? As it's microbore, should the whole system be replaced? Or, should the system be cleaned and flushed, radiator by radiator; then pressure clean the system as a whole; then change the boiler; then add the new piping and upgrade with thermostats? I've had a few opinions from both builders and plumbers. One suggested keeping the piping and changing the rest, the others to change the whole system. A major disruption to change the piping:- either buried in the solid ground floor or twisting everywhere under the upstairs floorboards. Your opinions all gratefully accepted!

RicK

 

[rick]

If you are near West Lancashire i will come out at no cost and tell you what I think you should do - your question and explaination touched me

cenrralheatking

Thanks Centralheatking, I'm touched but also a little bit embarrassed! Mum's fine. I'm just trying to get her to spend some of her saved up thousands on home comfort for if/when she can't get up the stairs! The description was just to introduce the situation/context. Dad looked to change the Concorde boiler for a similar cast Iron Baxi when you still could, about ten years ago, but he never got round to it. He always worried about the Concorde boiler failing, but it saw him out!

 

[Reg Man]

Hi everyone,

I'm a new member and not a plumber or central heating engineer.

Mum and me live in a 1970 house she's had from new and the installed central heating is very primitive (no thermostats except the one close to the Concorde boiler, no zonal valves). As far as I know, it's never been cleaned. On the Concorde, the electronic ignition gave up long ago, but apart from that everything works fine. All radiators are hot, there's no leaks and none ever need to be vented. It's even got some ground floor underheating due to the presence of the microbore pipe runs! Maybe it's living on borrowed time? (there is a fair bit of kettling!)

Either way, looking to have a groundfloor extension made, so that Mum can live downstairs. Extra rooms needed for bedroom, downstairs bathroom etc. Therefore, will need to add extra heating and will look at the very least to change the boiler to go along with the extra piping and radiators. How further does everyone thing I should go? As it's microbore, should the whole system be replaced? Or, should the system be cleaned and flushed, radiator by radiator; then pressure clean the system as a whole; then change the boiler; then add the new piping and upgrade with thermostats? I've had a few opinions from both builders and plumbers. One suggested keeping the piping and changing the rest, the others to change the whole system. A major disruption to change the piping:- either buried in the solid ground floor or twisting everywhere under the upstairs floorboards. Your opinions all gratefully accepted!

RicK

Bin it.

 

[Reg Man]

Bin it.

Not the most constructive comment: Micro bore was a great concept in its day, but now tried and tested, does not work over the long term due to the restrictive flow, debis build up. so fresh new eco friendly system required.

 

[rick]

Not the most constructive comment: Micro bore was a great concept in its day, but now tried and tested, does not work over the long term due to the restrictive flow, debis build up. so fresh new eco friendly system required.

Micro bore seems to get quite a polarised view. I'd like to get rid of it, but if it's worked so well, for so long without the old/current system being ever cleaned or flushed? New piping is a big upheaval, I envisage more so than extension. The engineer who has done inspections in the past is the one who suggests keeping the micro bore and piping generally, but changing everything else.

 

[Reg Man]

Micro bore seems to get quite a polarised view. I'd like to get rid of it, but if it's worked so well, for so long without the old/current system being ever cleaned or flushed? New piping is a big upheaval, I envisage more so than extension. The engineer who has done inspections in the past is the one who suggests keeping the micro bore and piping generally, but changing everything else.

Its done very well, but it is 42years old and heating systems don't live for ever. You could try to nurse it but I think the problems will keep popping up in the longer term.

 

[rick]

Its done very well, but it is 42years old and heating systems don't live for ever. You could try to nurse it but I think the problems will keep popping up in the longer term.

Yes, I take your point OK. It's all copper. How it's buried in the skreed? Are there kinks? Will it stand a pressured system. Will it thoroughly clean with a flush? As it stands, hopefully keeping it means no redecoration, no floorboards, carpets up .... If it doesn't handle a pressure test or fails in the future then go for a full repipe. That's the plan? (as it is!)

 

[rick]

OK. Been round in circles a few times and finally resigned to having to scrap/bin the whole lot.

To free up the cylinder space and hopefully keep a fast hot water response/ get a quick fill of Mum's baths/ run a couple of showers at the same time ... I was thinking of going for a combi with small local cylinder built-in.

Is it Wworcester 440CDI. or should I go for Veissmann 222 or the Valliant 937?

 

[michael c]

If the cylinder cupboard space is too important i would look into fitting a standard combi linked with an indirect cylinder or unvented cylinder. You could then pipe kitchen, sink and shower from the combi and baths and other shower from cylinder. Although i have never dealt with the 3 combi's you mention a friend fitted the valiant 937 for his parents 3 years back and have no issues so far.

 

[henly1234]

A pressure test is a simple affair you can do it with a car tire inflator you only need to pressurise to about 3.5 bar that will tell you if you have any leaks and its enough to stand a combi system. Ive been in this game now for over 35 years and I can tell you with authority that micro bores are the best with a closed system you don't need massive amounts of water moved to heat a house as long as its a steady flow and return, debris and sludge will not be a problem as long as it is well maintained with good cleansing and inhibitor, get yourself a descent plumber is my advice not one who's soul aim is money making, one who takes pride in his work and profession, and one whos got a bit of experience under his belt.

The problem with micro bore is not the system but the people installing it, most plumbers have no experience with it and so are very reticent to try something new when they've tried and trusted 15mm systems we are not the most innovative bunch, but if you've got a plumber who's a bit long in the tooth (hem) he will most likely have come across them in the past, after the war when stored water came into effect ( again continentals don't store water) and central heating came in we tried to emulate the systems used on the continent but because open systems were in use in this country, it was a massive failier because sludging is caused by black rust (more water than oxygen) and that caused the systems to block.

as far as boilers are concerned you are asking a lot, physics prevent water being heated up in the quantities you are asking for, combis gain in that they they will supply hot water for ever and a day and not run out like a cylinder but the flow rate is much less, best bet is to get a combi with a separate h/w flow through the heat exchanger, Intergas do one that is very good 22mm flow and only 3 moving parts.

 

[michael c]

You also have the option of a combi for most parts and then an electric shower. This will allow two showers to run at the same time however depending on your initial incoming flow rate/pressure you may have a reduced pressure whilst running two together.

 

[rick]

If the cylinder cupboard space is too important i would look into fitting a standard combi linked with an indirect cylinder or unvented cylinder. You could then pipe kitchen, sink and shower from the combi and baths and other shower from cylinder. Although i have never dealt with the 3 combi's you mention a friend fitted the valiant 937 for his parents 3 years back and have no issues so far.

Thanks, I thought that was thde idea behind those three boilers - they have a cylinder built in?

 

[rick]

You also have the option of a combi for most parts and then an electric shower. This will allow two showers to run at the same time however depending on your initial incoming flow rate/pressure you may have a reduced pressure whilst running two together.

Cheers, would those boilers handle two showers on together? What sort of water pressure in do two showers need/ Do you have to have 22mm pipe largely all the way to the showers or doesn't the pipe size matter?

 

[rick]

A pressure test is a simple affair you can do it with a car tire inflator you only need to pressurise to about 3.5 bar that will tell you if you have any leaks and its enough to stand a combi system. Ive been in this game now for over 35 years and I can tell you with authority that micro bores are the best with a closed system you don't need massive amounts of water moved to heat a house as long as its a steady flow and return, debris and sludge will not be a problem as long as it is well maintained with good cleansing and inhibitor, get yourself a descent plumber is my advice not one who's soul aim is money making, one who takes pride in his work and profession, and one whos got a bit of experience under his belt.

The problem with micro bore is not the system but the people installing it, most plumbers have no experience with it and so are very reticent to try something new when they've tried and trusted 15mm systems we are not the most innovative bunch, but if you've got a plumber who's a bit long in the tooth (hem) he will most likely have come across them in the past, after the war when stored water came into effect ( again continentals don't store water) and central heating came in we tried to emulate the systems used on the continent but because open systems were in use in this country, it was a massive failier because sludging is caused by black rust (more water than oxygen) and that caused the systems to block.

as far as boilers are concerned you are asking a lot, physics prevent water being heated up in the quantities you are asking for, combis gain in that they they will supply hot water for ever and a day and not run out like a cylinder but the flow rate is much less, best bet is to get a combi with a separate h/w flow through the heat exchanger, Intergas do one that is very good 22mm flow and only 3 moving parts.

Thankyou again henly1234. I must stress it's with great reluctance that the microbore is going. I can see your argument about how efficient and elegant it can be used. The trouble is, that it's been down for 42 years as part of an open-vented system. So just don't know how corroded they might be. The ground floor piping is probably just 'set in' the solid skreed. Who knows what state the twin-entry valves are in?

When building work proper gets underway, maybe if the microbore isn't skreed in but found to be in channels & maybe when the system is drained and a black sludge doesn't come out ??? perhaps keep. So, yes, if they do a pressure test before start pulling it apart in the hope of keeping some of it? But the radiators need changing? The twin entry valves need ditching?

 

[michael c]

15 mm pipe size to showers is ample. The boilers you mention should cope with two showers fairly well. However it is just my opinion but i would rather have a seperate cylinder or electric shower if you have more than one bathroon. This is purely down to future safe gaurding as you will still have the ability to heat water if any faults were to occur with the boiler. It also depends really on what you want personally from your system.

 

[rick]

15 mm pipe size to showers is ample. The boilers you mention should cope with two showers fairly well. However it is just my opinion but i would rather have a seperate cylinder or electric shower if you have more than one bathroon. This is purely down to future safe gaurding as you will still have the ability to heat water if any faults were to occur with the boiler. It also depends really on what you want personally from your system.

Thanks, it will be rare in the immediate future that both showers are used at the same time. Maybe just with visitors when we're all going out together/ getting up together _ ie. not that often! A pity that those models don't put an immersion in their integral cylinders - they must be supremely confident that their boilers won't fail!

 

[michael c]

those boilers are more of a space saving idea imo for those who dont want a big cylinder but still want the benefits of one

 

[Centralheatking]

I would like to thank you for posting this question - all the answers will have
been very instructive for all who populate UKPF - to get 4 pages of replies
of excellant info is a really positive vindication for ukpf - well done everbody

any praise from moderators ?

centralheatking