Types of central heating pipework

[SilverShadow]

Hi there,

 

We're looking to replace our CH system from the Jurassic era. This will involve installing a new combi boiler (to replace old gravity fed boiler) & 8 double radiators (replacing the old single panel ones). As the system is so old (i'd guess >30yrs at least, probably 40+) we imagine it'll need a whole new pipework system (especially as the combi will be in a different location), so plan to replace the old pipes

 

One plumber mentioned using MLCP - has anyone any experience of this type of pipework? While it's cheaper & more flexible, i wasn't sure if anyone had concerns over durability and if the connection joints degraded over time with systems like a combi?

 

We'll probably end up with copper pipes & soldered joints, but always worth asking around before making a choice - Pros & cons are always worth thinking about up front!  

 

 

Thanks for your time & thoughts

Shadow

[JohnMo]

Double post?

[SilverShadow]

Indeed - the last one i mistakenly put in the wrong thread, so opened this one here

[JohnMo]

1 hour ago, JohnMo said:

Thought they were old hat now as well!

 

Not a fan, it's not something you can easily modify without the correct tooling. If flexible pipes just go Hep2O, spares available on Sunday morning from Screwfix etc.

 

Combi isn't high pressure, the heating system will be set at around 1 bar.

 

The correct way to do the heating system 

 

Size radiators for room heat loss. Not a finger in the air.

 

Design for as low a flow temp as practical - make heat pump ready. Will be cheaper in the future and every heating day with gas. Aim for max flow temp of 35 degs.

 

Would do copper and press fit or push fit or Hep2O.

 

Choose your boiler based on modulation. Combi boiler is likely to rated at 30kW+, the average house in the UK needs around 6kW of heating on the coldest day. At 7 degs they need half of that. So a boiler that modulates down to 10kW will live a life of excessive cycling, leading to poor installed life and excessive heating costs.

 

So you need room by room heat loss, this will give you your total heat loss, now you want a boiler that modulates to at least half of that.

 

Running your heating - the normal (Jurassic mode) is on off time schedule. This isn't the most efficient, weather compensation or room compensation is more efficient, more comfortable and room temps can be cooler and way more comfortable.

 

Boiler choice is key.

 

Radiators - flow balance is key, they need to heat up at the same rate, normal way is lockshields and to cover a job badly done is a TRV to shut off the radiator then on then off. The better alternative (goes hand in hand with heat loss calculation) are these

https://pirateheatingsupplies.com/product/frv-flow-regulating-valves/?gad_source=1&gad_campaignid=22603472091&gbraid=0AAAAA_uQOsI4YNapY2Wj7rOPA1rRFVJSP&gclid=CjwKCAiA1obMBhAbEiwAsUBbIj-uN1P_BLT9iUQTLU-V8ZHZb3orWmRQPPXZlbzEVr58-MFTt1xrsRoCeBIQAvD_BwE

 

Lets the installer calculate and see actual flow rate.

 

Maybe a bigger reply than you wanted

From the other thread before it closes

[SimonD]

2 hours ago, SilverShadow said:

One plumber mentioned using MLCP - has anyone any experience of this type of pipework?

 

Yep, I have 100s of meters of the stuff in my store and it's very good. If I'm doing large installation work, MLCP and the fittings are what I pick up in preference of both push-fit plastic and copper. 

 

However, if I'm having to run new CH pipework through existing floors and joists, plastic layflat push-fit pipe is my choice as it's easier to work in these kinds of situations than MLCP. But in other situations it's not as good because it expands much more at high temperatures and the clipping distances are silly short - like 300mm on the horizontal - and it doesn't self support, so it sags. With MLCP clipping distances are over 1m and it has inherent stiffness and memory so when you bend it, it stays bent. Plastic doesn't stay bent but has a very annoying memory (even the layflat PB type)

 

The big disadvantage with MLCP is that you typically need an expensive press-fit tool along with expensive jaws for each size of pipe you use. But you can now get manual press tools that are a lot cheaper and some manufacturers now have compression fittings available - I've even seen a German manufacturer with a push-fit fitting for MLCP but no sign of it over here.

 

With MLCP you can also get pre-insulated pipes which save time and effort where you need insulated runs for the installation.

 

Your other advantage with both plastic and mlcp is that you can run continuous lengths and minimise joints throughout the installation.

 

Copper is very expensive now,  requires lots of joints, and if you have runs in existing floors, it's just a pain. Even if it is pretty when first installed and polished, this tarnishes over time. 

 

Overall, with the brands I use, MLCP actually comes in at better value than plastic, believe it or not, and it has slightly reduced installation time overall even in retrofit jobs. What's also nice about MLCP is that you can dry fit all your joints without fixing them and then when you're ready go through it all with the press tool. Another small thing, that can sometimes be really important is that the sealing of MLCP is on the inside of the pipe. On plastic, it's on the outside, so you have to be careful you haven't damaged the surface of the pipe. With MLCP this isn't a problem.

 

Since I've used MLCP I haven't had a single leak on an installation. That's more than I can say for copper and solder! And there's no hot works or stinky soldering!!!