micro bore pipework

[melleka]

I would like to change the pipework on my central heating system from micro-bore 8mm to at least 15mm I can easily access the downstairs radiators from under the floor void space but would with upstairs being laminate flooring I will have to keep it micro-bore. Will this cause a problem All the radiators are the double entry valve type and would like to change them to inlet and seperate outlet, at least the downstairs. Will it be easy to change from micro-bore to 15mm on the multi-point branch, I think it is 15mm. What are the advantages of having micro-bore, or are their any!!!!!!!!!!!
Many thanks if anyone can help. I fear this will not be my last enquiry on this site.

Melleka

 

[chrishutt]

Why do you want to change from microbore?

If the system is properly designed and installed, there are no disadvantages to microbore. Double entry valves can be replaced with separate flow and return valves still using microbore.

 

[ollski]

Why do you want to change from microbore?

If the system is properly designed and installed, there are no disadvantages to microbore. Double entry valves can be replaced with separate flow and return valves still using microbore.

Well except that it kinks easily when you knock it, blocks up easily, looks nasty and is at the exact level where kids smash their tonkas into it.

 

[chrishutt]

Ollski, I beg to differ. I've been installing microbore for 25 years and I don't recognise any of those things as problems.

In fact microbore can look much better than 15mm because it can be easily concealed behind, or clipped along, skiting boards. As for blocking, no reason why it should unless there's a lot of rubbish in the system, in which case even 15mm can block.

 

[ollski]

Ollski, I beg to differ. I've been installing microbore for 25 years and I don't recognise any of those things as problems.

in which case even 15mm can block.

Agreed and it does frequently although it takes a lot longer than microbore I just don't like it and can't think of a decent advantage on why to have it. Decent installers can make a half decent job of it but its usually budget first fix material half blocked with solder, kinked where its been pulled through holes and forced into unnaturally square bends etc. I'm sure you're one of the better ones though chris . Still saying all that in my mind it's better than the plastic rubbish used in first fix now.

 

[Paul Barker]

We have estates round here where they used plastic 8mm. It comes out of the wall at all sorts of odd angles and contorts it's way into the valve somehow. When doing a boiler change and the necessary upgrade to trv's it costs more because 8 mm trv's cost more and is a hell of a problem to work with, not the least because with plastic you have to cut the pipe behind the olive so it's now too short, but the blessed way it comes out at an odd angle through the plaster of the wall it can't be pulled longer that easily in all cases.

They do seem to suffer blockage more quickly than 15mm copper too. Of course I use plastic these days also but only where nobody can see it, wouldn't like to own up to it.

 

[chrishutt]

I didn't know you could get 8mm plastic. The only stuff I've ever seen in plastic is 10mm, although the bore is slightly smaller than 10mm copper. And TRVs with 8mm or 10mm connections don't cost significantly more in my experience.

The major advantage of microbore is in speed of installation, although with 15mm plastic now an established option, this is not so significant as in the all copper days. Still its smaller size allows it to bend more tightly and it's easier to conceal behind skirting boards and bury in plaster.

Finally microbore installations, properly designed, tend to be self-balancing in that each circuit will have a proportionate resistance without having to adjust lockshield valves.

 

[melleka]

It looks like I have opened up a can of worms!!!!!!!!
I think I will keep with my microbore and re-route or piece-in extra lengths to suit the new radiators for inlet one end, outlet the other. I read that you can get valves that suit microbore pipes 8mm, are they easily available from plumbing merchants???

My thanks to you all for sharing your views, it's better than calling in a plumber and getting a shaking of the head and a " it's a big job mr's.....it's going to be expensive" reply.

 

[chrishutt]

Yes you can get 8mm rad valves easily. But while you're at it, why not fit Thermostatic Rad Valves? They may cost a bit more (£5+) but the fitting is just as easy/difficult.

You'll also need 8mm connectors (straights/elbows) to extend existing pipes. End feed solder is cheapest if you can solder OK.

 

[melleka]

Yes you can get 8mm rad valves easily. But while you're at it, why not fit Thermostatic Rad Valves? They may cost a bit more (£5+) but the fitting is just as easy/difficult.

You'll also need 8mm connectors (straights/elbows) to extend existing pipes. End feed solder is cheapest if you can solder OK.

Thanks Chrishutt

I do not have any TRV's fitted at present as my system does not have a by-pass. I have a back boiler that I want to do away with and get a Condensing boiler fitted under the stairs so that I can fit a proper flush fire in place. The system I have is an indirect. If I have a Condenser ( or combi, don't know which is better??? ) I can do away with the loft tanks and the hot water cylinder in the bedroom cupboard.

Hope I am talking sense here!!!!!!!! All info is from my limited experience and reading books on Central Heating systems.

Cannot solder, o.k. on circuit boards, that's my limit.

Thanks again......................I'll get there.

 

[bathjobby]

A condensing boiler still requires a hot water cylinder and F/E tank, you can get rid of those with a combi though.......

 

[melleka]

In your opinion what is the best combi boiler on the market?
Can they be fitted under the stairs with a flue going to the outside?
Will I be able to fit all my radiators with TRVs

Cheers

 

[chrishutt]

There was a recent posting on "what is best boiler?" theme. You tend to get what you pay for, but Vaillant and Worcester usually get mentioned.

As for location, you need to discuss that with prospective installers. Depends on practicalities of flueing and re-routing pipework. Bear in mind that condensing boiler fumes will contain a lot of water (steam to non-pedants) and this "plume" might be a nuisance if flue terminal poorly located.

You certainly can fit all your rads with TRVs but boiler may require external by-pass to allow for occasions when all TRVs are shut. One rad always open (e.g. towel rail) can be sufficient for a by-pass.

Just to clarify, a combi boiler is one that also provides instantaneous hot water (no need for cylinder, feed tank, etc.). A combi can be condensing or non-condensing, although building regs now require condensing boilers to be installed in almost all cases.

 

[melleka]

Thanks very much Chrishut. I feel I have learned a great deal about central heating over the last few days.

Many thanks again

Melleka

 

[Paul Barker]

Melleca it's required now to use a room thermostat and some form of time control. It is also a requirment that the radiator/s in the zone where the room thermostat is fitted should not also be trv controlled. Any bipass you fit should now be automatic, but check manufacturers instructions because most have been forced to include a bipass inside the boiler in the face of problems in their boilers caused by fitters not installing them. All pipes outside the heated area should be insulated at least the diameter of the pipe in thickness.

The list is endless.....