Can anyone suggest a cost effective way of running a htg flow & rtn underground for 2m to a workshop?

I fully realise it needs to well insulated, but I can't find anywhere that will do me a 4-5M length of insulated 15mm twin pipe

Just so you're aware, it will be controlled via its own zone valve and only occasionally used. We aim to bury at least 400mm down to top of the outer casing. It will come up inside the two buildings.

Thanks

Where are you in the Country I have some neoprene pipe insulation, I can't remember the diameters, same as Armaflex. As DarylP says, make your own. If you're worried about heat loss you could also look at trace heating to the pipework, before you insulate. For a DIY job how about fitting the pre insulated F&R inside a large dia. PVC pipe and foaming all around. The Solar thermal suppliers sell flexible pre insulated pipe.

It might also be worth using a smaller diameter pipe - it depends on how big the radiator(s) is/are and how the circuit is pumped, of course.

Posted By: owlmanTrace heating is not only used to protect from frost, it can also be used to maintain or even raise fluid temps in the pipework

Are there many domestic situations where that is preferable to increasing the level of insulation? And/Or designing for the slightly reduced flow temperature?

In the present case, for example, would trace heating not require an extra control system to sense when flow was active in the circuit in order not to waste energy heating an unused pipe for long periods?

Posted By: barneyIt is regularly used to maintain pipe temperature on long single leg systems as an alternative to circulation return systems on domestic HWS (as an example) - so you don't have to wait an age before you get hot water at the tap - and as a method to combat legionella growth

Are there many well-designed domestic systems where there are long runs or where legionella growth is an issue?

And in the UK, is it justifiable, in a green sense, to consume energy to save water?

I do know of a few instances where it's been used to provide a top up space heating source (actually a towel rail circuit used in the summer when the heating is off) - although a radiator immersion heater is probably more usual

Using it for space heating does sound reasonable, though why anybody would want to heat a towel rail outside the heating season is questionable, IMHO.

Do a google search for "Pre-insulated district heating pipe"

Should come back with a few options

Well - I guess it depends on how you describe "domestic"

Building services engineers will describe hot and cold water systems in all buildings as "domestic" - other people will think of only those hot and cold systems in "domestic residences"

In many cases, there is a balance between the number and optimum position of any HWS storage and the points of utilization and from there we get into the details of if the pumping energy and heat loss of recirculation is better or worse than a single leg and use of trace heating for temperature maintenance - the extra copper and the pump all has an "energy" burden in reality. Available fuel sources will also influence the approach.

As an example I know of a domestic HWS system in a hospital that uses centrally fired oil as the heat input - it's a 100% recirculation system - probably about 90% of the input energy is lost every day compared to usage due to losses and pumping energy - it wouldn't be difficult to show an improvement with using trace heating and avoiding some recirculation

Legionella is certainly an issue in under utilised outlets (things like showers having occasional use in maintenance areas as an example). It's a matter of dialogue if the system is through "tech" using a temperature maintenance approach or through manual intervention - eg opening and running sentinel outlets on a regular basis - you need a reliable FM person for the latter - the former is "lower risk" for a designer and building owner/operator

Regards

Barney

Same answer really - if you have a free hand to get the HWS generation/storage local to the points of utilisation then the amount of dead leg waste and "annoyance" factor of waiting for hot water is minimal

If you can't achieve that, then it's worth looking at recirculation (twice the pipework and pump plus energy plus the heat lost from recirc) or temperature maintenance with trace heating (capital cost balance and energy cost to maintain temperature via a higher carbon electric input)

I guess it depends on a specific location and set of circumstances - it's certainly regularly used to maintain pipe temperature on domestic systems where optimum positions, dead leg lengths etc conspire against the designer

Regards

Barney

Indeed - but plenty of consumers want instant hot water with no lag - typically the same people who want 10kW electric body blowers when they step out the shower on to a heated tile floor

I wasn't suggesting it's a brilliant idea in terms of energy consumption - it's a solution however to meeting consumer demands where recirc isn't an option

Regards

Barney