Replace micro-bore with 15mm?

[gwernybwch]

I've got a 3 up, 3 down Victorian house which I'm going to shortly start updating room by room.
It has GCH in the property. The radiators (I'm guessing) and copper microbore pipe system was fitted about 20 years ago. Initally it had a back-burner and a cylinder, but those were replaced with a combi-boiler about 5 years ago.
I intend to replace the radiators in each room as I go and microbore being microbore, I doubt that I will be able to remove the old radiaor and fit new ones without having making some adjustments / repair to the pipes.

Some I'm wondering whilst changing the radiators, is it worth taking out the micro-bore as well and fitting it with 15mm?

Will it create issues if part of the CH is on 15mm and the rest on micro-bore?

NB: I want the entire house to be copper pipes. I'm got some experience of fitting (soldering, bending etc) 15mm copper pipes now, but little experience with micro bore.

Thanks in advance for any replies.

 

[23vc]

Definitely worth changing it, you may find the main feed and return are 15 or 22mm and it changes to microbore for each radiator in which case you won't need to change it all. If it's a combi sealed system I'd use pushfit for everything out of sight as the time saving is massive, and less intrusive for getting through joists. Then nice copper and endfeed where you can see it. Even if a pushfit goes pop (v unlikely nowadays if fitted right) you're not going to get a house destroying flood just a few buckets worth. That's just how I do it I'm sure others will have their own thoughts!
Also you may find the boiler fitter won't comisson it anyway if there's cr&p old microbore
Cheers
John

 

[Agile]

You really need an engineer to see if you can preserve the DHW while the entire system is drained to give you a few weeks to replace all the CH pipework.

Tony

 

[Steelmasons]

A few weeks???..

 

[Agile]

A DIYer is unlikely to repipe a whole house and fit new rads in a short time if he is working full time as most of us have to do.

Tony

 

[DP]

OP, why not keep the microbore. Why the urge to replace with 15mmif system works
Chances are your system was probably fitted by a pro who knew his materials and trade

 

[Aquaheat]

A few weeks???..

At £84 quid an hour that's a bargain steels! And you thought Tony couldn't price up properly.

 

[Razor900]

If it all works I would just change the rads, you will probably be able to bend the pipes by hand to suit the new ones

I don't know what's more scary; weeks to change the pipework or a fitter refusing to commission a boiler because the pipes are microbore

Luckybags eh @Steelmasons?

 

[Agile]

You have not bothered to tell us what make of combi you have.

Worcester is a major boiler manufacturer and they refuse warranty cover on boilers fitted to microbore systems!

They say their boilers are not suitable for microbore!

But the inside of their boilers is fairly similar in function to any other boilers! Just more plastic and so cramped that maintenance is difficult.

Tony

 

[Agile]

There are two common sizes for microbore, 10 mm and 8 mm.

10 mm will give reasonable performance if well designed.

8 mm is much more troublesome!

Tony

 

[Razor900]

Worcester is a major boiler manufacturer and they refuse warranty cover on boilers fitted to microbore systems!

They say their boilers are not suitable for microbore!

But the inside of their boilers is fairly similar in function to any other boilers! Just more plastic and so cramped that maintenance is difficult.

Tony

Is that actually in the manual Tony??

I think @boilerdoktor would be able to confirm that. No fan of WB but I would be very surprised if they stated that

 

[gwernybwch]

Thanks all for the replies

Definitely worth changing it, you may find the main feed and return are 15 or 22mm and it changes to microbore for each radiator in which case you won't need to change it all.

Can you explain this in more detail?
If the flow and return are 15mm / 22mm and microbore is only on the feeds to the radiators, is this how a 'good system' would be set-up? But if the main / return are also microbore that this - ideally - should be upgraded? Have I understood that correctly?

@Agile sorry I didn't realise that the brand of boiler was important. It is a Worcester Greenstar (not sure what model). I don't recall my heating engineer didn't mention anything about potentially invalidating the guarantee of the boiler by using it on a microbore system (although he might have done so because he was muttering a lot about the 'bloody microbore'!). The combi's been in place for 5 years now, so well out of any warranty period.

 

[St0rmer66]

Worcester have no such disclaimer about microbore anyway. All they're bothered about is if it's clean water going round, the rest of the system is almost irrelevant to them for warranty purposes.

 

[DP]

Any pipe, be it straw diameter to king size pipe, it will slow the medium flowing through it.
However, there is a cross over point where the pipe needs to go to the next size up

Microbore tube like any other tube will have load to distance curve

The installer needs to establish if a radiator will get sufficient quantity of water so that it will give out required amount of heat. Oversize, then you will need to throttle down the lock shield. Undersize, you still get flow but insufficient to give you rated heat output

This scenario commen to gas lines too. Often new boiler fitted but gas line sometimes as was. So shiny new combi fires for hot water, gas hob burners downsize.

 

[boilerdoktor]

Thanks all for the replies

Definitely worth changing it, you may find the main feed and return are 15 or 22mm and it changes to microbore for each radiator in which case you won't need to change it all.

Can you explain this in more detail?
If the flow and return are 15mm / 22mm and microbore is only on the feeds to the radiators, is this how a 'good system' would be set-up? But if the main / return are also microbore that this - ideally - should be upgraded? Have I understood that correctly?

@Agile sorry I didn't realise that the brand of boiler was important. It is a Worcester Greenstar (not sure what model). I don't recall my heating engineer didn't mention anything about potentially invalidating the guarantee of the boiler by using it on a microbore system (although he might have done so because he was muttering a lot about the 'bloody microbore'!). The combi's been in place for 5 years now, so well out of any warranty period.

Agile is talking nonsense , Worcester will not invalidate your warranty, if anything they are a lot more forgiving than other manufacturers