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Microbore for radiators


Stephen Jeavons

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Hi All,

Due to a school-boy error (pressure from elsewhere to re-fit the interior in quick time) I've found myself needing to re-install the central heating on my 70' narrow-boat with limited access to run conventional pipework to radiators. Having owned a number of domestic properties which had microbore radiator plumbing, I was exploring the option of using it (the later plastic variety, not copper) on the boat. Anyone have experience, good or bad of doing this? It would solve my problem as no joints in awkward places would be required between manifold and radiators.

Stephen 

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My experience of microbore heating runs in a house is that it gets blocked. Yearly power flushes don’t clear it either. It also requires a more powerful pump to move the water through the system. 

Whether or not the above has any real relevance to a narrowboat I’m not sure. 

  • Greenie 1
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I would go further and say the greater the pressure a pump has to act agains the higher its current consumption - not something I would have though ideal on a boat unless its always on a shoreline.

Also plastic pipe seem to expand more that copper and sag when hot so will probably need boxing in for aesthetic reasons.

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13 minutes ago, Tony Brooks said:

I would go further and say the greater the pressure a pump has to act agains the higher its current consumption - not something I would have though ideal on a boat unless its always on a shoreline.

Also plastic pipe seem to expand more that copper and sag when hot so will probably need boxing in for aesthetic reasons.

How much does speedfit expand when hot, does anyone know?

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All I can add is that in the late 70s early 80s loads of people started having the " in thing " fitted which was microbore central heating. It wasn't long however before everyone seemed to be fitting 15 mil arf inch again. In houses I mean.

Edited by mrsmelly
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We have microbore central heating in our house which was built in 1994.

It has never blocked or caused us any issues what so ever (touch wood). We have just had a new combi boiler fitted at home so it will be interesting to see if we have any problems after this.

Some interesting comments on MB systems here.

http://www.combico.co.uk/micro-bore-pipes-for-central-heating-systems/

Edited by MJG
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Yes, interesting that. Strangely enough, all 3 of the houses I've owned and at least 2 that I've rented have all had microbore and I too never had an ounce of trouble. I even retrofitted restored old iron radiators in 3 of the rooms in one (they were great) without an ounce of trouble. I guess regular maintenance and ensuring that the appropriate rust inhibitor is added is the key. 

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6 minutes ago, MJG said:

We have microbore central heating in our house which was built in 1994.

Same year ours was built. 

1 minute ago, Stephen Jeavons said:

I guess regular maintenance and ensuring that the appropriate rust inhibitor is added is the key. 

Hasn’t helped us :(

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39 minutes ago, MJG said:

We have microbore central heating in our house which was built in 1994.

It has never blocked or cause us any issues what so ever (touch wood). We have just had a new combi boiler fitted at home so it will be interesting to see if we have any problems after this.

Some interesting comments on MB systems here.

http://www.combico.co.uk/micro-bore-pipes-for-central-heating-systems/

Alot of the advantages of microbore seem to have the same advantages of plastic pipes - ie. reduced joins, easy of installation.

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2 hours ago, Dave Payne said:

How much does speedfit expand when hot, does anyone know?

JG Guest Speedfit says    1% on length.   20C. - 82C.     Pipe clip spacing :-              Horizontal              Vertical 

                                                                                                          15mm            300mm               500mm

                                                                                                          22mm            500mm              800mm

                                                                                                          28mm           800mm              1000mm

Edited by Flyboy
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Why do you need to use microbore? 15mm plastic is available and can be threaded fairly easily. You also need to take into account the carrying capacity of the pipe to ensure it can carry sufficient water to keep the radiators hot. There are charts available on pipe sizing on the web. Remember, when used in houses, microbore is used over relatively short distances to individual radiators from a manifold that is fed by much bigger pipes. What pump do you have? If a standard domestic circulator, then distance on a boat should not be a problem, but if a small 12 volt pump, it may struggle. The pump curve in the spec will confirm the performance.

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The reason I'm considering it is because I don't have enough space for a pair of 22mm or even 15mm pipes. I can buy a coil of plastic or copper microbore and thread it where it needs to go without having to join it. My shore-powered electric boiler uses a standard domestic mains circulator. However the Eberspacher will be using its own so therein lies the gotcha. The mains system may work fine with the microbore but the diesel powered one with its 12v pump may not. Both heat sources are plumbed in parallel with isolators to use one or the other depending on whether we're plugged in or cruising.

It's only the two rads at the front of the boat that I'm considering feeding with microbore due to space/access restrictions through the kitchen. Bathroom, engine-room, back cabin and calorifier are all 15/22mm. Unfortunately those two radiators are furthest from the heat source which is in the engine room. 

Will do the radiator calculations and have a re-think. My original query was just to sound out whether anyone on the forum is using microbore on their boats for whatever reason. So far the answer is NO!

Thanks very much for the insight guys.

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1 hour ago, Stephen Jeavons said:

However the Eberspacher will be using its own so therein lies the gotcha.

 

I'm surprised no-one has suggested reading the Eberspacher instructions for advice. Or maybe you have and it says pipe up in 15mm or larger and you are thinking of ignoring it.

Not a great idea regardless of what others might tell you. 

  • Happy 1
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Hi Mike,

As it happens, the installation  manual I have is the one I got when I bought the boat and unfortunately it relates to the fitting of the unit to a motor vehicle. No 15mm pipes mentioned of course.

if anyone has a Marine version of an installation manual for a Eberspacher D5W to share, I would be grateful.

Anyway just to clear any misunderstanding, the piping to and from the Eber is 22mm. Ditto to the rear radiators and calorifier. I only wish to use micro bore on two front radiators not the entire system. I hope that makes sense.

 

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I would think it is the same as webasto that says ues 22mm pipe for flow and return, I was told it was because the circulating pump is very small it cant cope with any restriction that 10 or 15mm pipe would cause. NMEA would be able to give more info as he fits webasto and mukini.

Neil

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4 hours ago, Mike the Boilerman said:

 

I'm surprised no-one has suggested reading the Eberspacher instructions for advice. Or maybe you have and it says pipe up in 15mm or larger and you are thinking of ignoring it.

Not a great idea regardless of what others might tell you. 

Maybe because the Eberspacher was not mentioned until after many posts. The OP seems quite versed as to the limitations.

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If you do fit microbore make sure your refilling water is not hard water. We had it fitted in our house in a hard water area and it was partially blocked due also to lack of rust inhibitors. We had two power flushes which improved it for a while but I would have preferred 15/22mm copper. HTH

Cheers

David

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The way it's done on many Piper built narrowboats, using both Webasto and Eberspacher units, is to run 5/8 flexible rubber radiator hose from the engine space to the calorifier space  (midships) and then tap off that using a JG speedfit manifold to feed the rads in plastic 10mm (iirc) internal bore. The Eberspacher bloke at Crick told me they recommend at least 15mm pipework and have told Pipers this, but they keep doing it. My own preference would also be larger pipes, but the Piper way actually seems to work fine.

As for the pitfall of pipework furring up, I'd shell out a tiny bit more and use distilled water in the anti freeze mix. Pre mix to avoid poor flow due to stratification and don't go too high a percentage (I use 25%) or the heat transfer rate suffers.  It's important that the Eberspacher works hard or early failure is common, but if you have a D5w in a 70' boat it ought to be about right if used in bursts and not left on to to 'tick over'.  I say this so you give your unit the best possible chance should you elect to go for the smaller pipework. 

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19 minutes ago, Sea Dog said:

The way it's done on many Piper built narrowboats, using both Webasto and Eberspacher units, is to run 5/8 flexible rubber radiator hose from the engine space to the calorifier space  (midships) and then tap off that using a JG speedfit manifold to feed the rads in plastic 10mm (iirc) internal bore. The Eberspacher bloke at Crick told me they recommend at least 15mm pipework and have told Pipers this, but they keep doing it. My own preference would also be larger pipes, but the Piper way actually seems to work fine.

As for the pitfall of pipework furring up, I'd shell out a tiny bit more and use distilled water in the anti freeze mix. Pre mix to avoid poor flow due to stratification and don't go too high a percentage (I use 25%) or the heat transfer rate suffers.  It's important that the Eberspacher works hard or early failure is common, but if you have a D5w in a 70' boat it ought to be about right if used in bursts and not left on to to 'tick over'.  I say this so you give your unit the best possible chance should you elect to go for the smaller pipework. 

That's interesting, so a well known boat builder is routinely using 10mm microbore against advice and presumably not having problems. Well, like I said previously, I was only contemplating dropping to 10mm for the front two radiators and would feed the manifold for these with 22mm pipe. The use of distilled water sounds like a good idea too.

I still have a pile of other stuff to do before the central heating rises to the top of the to do list but will report back on how it all functions if I elect to go ahead with the 10mm pipe

Thanks everyone for the advice and comments

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3 minutes ago, Stephen Jeavons said:

That's interesting, so a well known boat builder is routinely using 10mm microbore against advice and presumably not having problems. Well, like I said previously, I was only contemplating dropping to 10mm for the front two radiators and would feed the manifold for these with 22mm pipe. The use of distilled water sounds like a good idea too.

I still have a pile of other stuff to do before the central heating rises to the top of the to do list but will report back on how it all functions if I elect to go ahead with the 10mm pipe

Thanks everyone for the advice and comments

In the mean time start collecting rain water for the system and engine and save on buying distilled water, although its not expensive from motor factors. A couple of washing up bowls on the roof to collect it and transfer, filtering it through an old T shirt or something into bottles or something. I do it all the time, always have done.  I use it for batteries, engines, car engines, heating the lot. My cat won't drink anything else. Many times I've mentioned this on here but not much response about it. Sometimes I use fresh river water, rather than tap water.

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22 minutes ago, bizzard said:

In the mean time start collecting rain water for the system and engine and save on buying distilled water, although its not expensive from motor factors. A couple of washing up bowls on the roof to collect it and transfer, filtering it through an old T shirt or something into bottles or something. I do it all the time, always have done.  I use it for batteries, engines, car engines, heating the lot. My cat won't drink anything else. Many times I've mentioned this on here but not much response about it. Sometimes I use fresh river water, rather than tap water.

Totally agree, I've always used filtered rain water in batteries but the last set gave up after only 9 years. My wife also uses it in her steam iron. Most 'distilled' water these days is not distilled anyway, it's de-ionised. The important thing is to collect it without it touching any metal, so directly from the sky into a plastic container.

Edited by Flyboy
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