Heating system pipe size question.

[Mottie]

Just curiosity really. We often go for breaks in the Peak District/cotswolds and I always noticed that heating systems in the places we rent have smaller pipes than down here. Why is that? What’s the advantage/disadvantage?

 

[Harry Bloomfield]

What’s the advantage/disadvantage?

The small pipes, block more easily.

 

[numpty1]

tight northerners will not pay for proper sized pipework

 

[gas112]

Cheaper and in theory easier to fit but not really .
Microbore used to be 8mm copper but now you get 10mm copper and plastic with 8mm rarely being used

 

[muggles]

The small pipes, block more easily.

Hmmmm yes and no.....

You're actually more likely to get sludge deposition in larger bore pipework due to reduced velocity. You get deposition below about 0.3m/s velocity. It's one reason we target 0.9m/s velocity in central heating pipework, and why sludge tends to collect in radiators where velocity is lower

 

[gas112]

Hmmmm yes and no.....

You're actually more likely to get sludge deposition in larger bore pipework due to reduced velocity. You get deposition below about 0.3m/s velocity. It's one reason we target 0.9m/s velocity in central heating pipework, and why sludge tends to collect in radiators where velocity is lower

but it tends to block in the actual manifolds which larger pipework doesnt have

 

[muggles]

Yes, velocity issues at the manifold which is usually 22mm. You'll get sludge deposition pushing anything less than about 8kW through that on a modern condensing boiler system, or around 4.5kW on pre-condensing era systems. If 10mm was used in a non manifold layout off a 15mm it would work much better (as would keeping the system clean of course).

 

[CountryFan]

tight northerners will not pay for proper sized pipework

So the same applies to new builds? Think I’ve only ever seen 10mm pushfit in these.

 

[muggles]

New builds go for 10mm as it's easy to get behind plasterboard, although with the advent of heat pumps and AD-L insisting on low flow temperatures they're going to need to start pushing some of that back up to 15mm again.

 

[desktop987456]

I think it all depends on the amount of heating load on a circuit - general rule of thumb is if heating load is greater than 8kw 22mm is preferred depending on the length of pipework.