Heat pump causes gas explosion

Was the explosion 'caused by the heat pump'?

Looks to me as though it was caused by an escaping pocket of underground gas, possibly released by the GSHP bore hole excavation, and ignited by an as yet unknown source.

Yes, very sad.

It was caused by the digging of the borehole, which could happen whenever a deep enough hole is dug, so saying it was caused by a HP is rather stretching reality.

There are some heatpumps which use flammable refrigerant which in the right conditions will go bang... in fact, almost everyone has one. They're called 'fridges'.

(apart from ye olde fridges which use good old ozone-destroying R12, most current ones use R600a which is isobutane)

Theo

The question to ask is whether it was anywhere near an abandoned domestic waste site.

Yes I should have said Heat Pump Installation in the title, it was the irony of the situation that piqued my mind though.

True, but most folk are unlikely to have bore holes dug unless for private water supply or, increasingly often, GSHPs. Shoulda stuck with an ASHP.

Just terribly bad luck really. I wonder if it’s in an old coal mining area?

Tim

Hopefully that would never be allowed!

Tim

The escaping gas from the borehole, had no mercaptan in it, so it is a naturally occurring gas, and not from the gas company. Apparently there were two incidents at the site, one in July, one in October. July was the opportunity to fix it.

I can see why they want to cordon the area, and make people sign a waiver to enter the area :-/

At some point, an approval was given to build on that site, and that would have been the opportunity to avoid this happening.

Paul

Is it routine to drill test boreholes on housing development sites to test for natural gas? There’s no sign of any landfill (present or historic) anywhere near to Cleat Hill. Not a mining area either as far as I can ascertain. Just terribly bad luck I think.

Tim

It's not, but natural gas is common in geological deposits. Basically it's just a natural compost heap and any organic (plant) matter decomposes anoxically to methane, just like a landfill site. Here the organic matter is usually trapped in aquatic sediments, eg river, sea or bog.

(usually such deposits are in tiny pockets not enough be economically viable for gas extraction - fracking is one way to open up such pockets for extraction.)

Interestingly Cleat Hill doesn't have any borehole records - I wonder if the contractors submitted a record of what they found.

Theo

If there is a possibility of this happening shouldn't it be the responsibility of the company that drilled the bore to have monitored for gas whilst drilling and a least for a short period afterwards?

It looks as if the explosion partly demolished the house. Was this as a result this of a build-up of gas within the property? If so how far was the bore hole away from the house for a gas lighter than air gas to enter the property? When installing LPG or oil there are regulations with regards how close the tanks can be, and more stringent if they are to be buried.

Look up Fairview, 7 Cleat Hill, Bedford, MK41 8AL.

It's a house on a main-ish road with a very long garden. The man killed (Paul Swales, aged 85) applied for planning permission to build a house in the garden, which was accepted on appeal. The new house had a new access made from Wagstaffe Close, opposite no.11. If you look there on Streetview you can see the borehole equipment.

Documents:

Unless the action of digging the borehole basically fracked the whole area and gas started coming up everyone's foundations? Which would explain why the exclusion zone is in place?

Theo

...

"The initial investigations by the gas distributor Cadent found that gas was detected at the scene; however, it was not the odourised supply that flows through its network and into people’s homes, but rather odour-free natural gas from a pocket underground. The source of the gas was a 100 metre-deep borehole drilled in July in the garden of the property as part of works to install a ground source heat pump, as has been pointed out. This encountered a pocket of natural gas. Following that, an attempt was made in July to plug the borehole to stop gas flowing to the surface, but this work was evidently unsuccessful as subsequently gas continued to leak. After the explosion in October, gas testing of the soil in the area conducted by the British Geological Survey found gas leaking to the surface over a wide area, requiring a 150-metre safety cordon and the evacuation of the homes inside the cordon."

Naturally occuring. A lot of Bedforshire is sand and shale not far under the surface [1], so natural gas is held by the sand and shale levels. Break the sand cover, and it escapes.

Reading the usual execrable BBC reporting a 'natural gas leak' would seem to be someone drilled through a gas pipe.

No the GSHP would probably use boreholes than crashed straight through a gas main

It wasn't a 'natural (gas leak) it was a (natural gas) leak - i,e, a drill through a pipe

Thanks for pointing that out.

When I read the article linked in the original post I was trying to decide: "Do they mean natural gas or Natural Gas?"

The English language has been uggbered to the point where the term used is completely ambiguous.

Reading the material from other sources, it seems that it is you who has it backwards.

Chris

Did you actually bother to read the BBC reports ?. NO.

The borehole hit a pocket of naturally occurring methane which was odourless, unlike the intentionally sniffy stuff delivered through yellow pipes.