Underground insulated pipe

[epatrickt]

I've a wood-fired boiler in my garage and have the flow and return going underground (about 10m + 2m in vertical) to the house. I put the pipe in on the cheap and used 32mm alkathene pipe lagged with Armaflex and surrounded in sand about a foot down.

I'm guessing that this is losing a lot of heat since there is evidence above where a short section of concrete path tends to stay dry.

I've had a quotation for the supply of some Flexalen, purpose-made insulated pipe but I am hoping to work out how much difference there will be in heat loss in order to work out if it is worth the outlay - that is, what is the pay back?

I have heat loss figures for the Flexalen but have no idea about the alkathene. Anyone know how to do a decent estimate for this please? The Flexalen is in the region £500 before the cost of punching holes through our (stone) walls so not trivial, but if it cut our fuel costs then it may be worth it.

Thanks

 

[JohnD]

more important is the thickness of the Armorflex you used.

 

[epatrickt]

Think the alkathene is actually 28mm (the connecting copper is 35mm). The Armaflex is 25mm thick.

 

[JohnD]

And how thick is the insulation on your proposed replacement pipe?

I have a feeling it will not repay cost of digging up.

25mm Armaflex is quite decent pipe insulation. The soil surrounding it will be warmed, yes, but that will reduce the temperature gradient.

 

[epatrickt]

Well it has an energy loss of 16.58W/m. It is 2x32mm pipes in a 125mm casing. Hopefully I have figured out the forum album and you can see a photo of it here.

Untitled

• epatrickt
• 11 Oct 2014
• 1

[/img]

I know that professionally installed biomass systems use this pipe but like you, I have doubts about the pay-back if the Armaflex is doing the business.