Hot water loop

[MdB]

1/ Incoming pressure fine.
2/ Pump and nrvs exactly the same on both circuits so no problem there
3/ Probably the problem

I'm still not convinced, you really need to do some tests. I would do the following and let us know the results.

a) Starting pressure reading (4.5 bar?)
b) Open hot tap - measure pressure whilst hot tap is open (1 to 2 bar?)
c) Close hot tap - measure pressure (3 bar?)
d) Leave system for 5 mins whilst not using any water at all - measure pressure (?)
e) Leave system for a couple of hours whilst not using any water at all - measure pressure (?)

If you do the above then we should be able to rule in or rule out some of the possible causes.

 

[Penners]

my water board man told me to ensure I ran water off from each stand pipe on a very regular basis

We're very advanced, here in Suffolk. We have water piped right into the house. :wink:

 

[Penners]

how could it be policed?

http://en.wikipedia.org/wiki/Water_police

 

[Flyfisher]

If they can send in those water police then I think they'd definitely have grounds for suspecting that someone has left the tap running.

 

[Aidan]

Could be a defective pressure gauge, loss of air charge in an expansion vessel, different temperatures, a leak from one system (the water pressure increases as the water heats up but drops again when some of the water is run off) a defective non-return valve letting the hot water expand back up the cold feed, a defective pressure relief valve and/or a defective pressure reducing valve letting-by, so the pressure creeps up.

Or something completely different.

Circulating loops are used in commercial premises to keep the DHW hot and keep the legionella at bay. You can achieve the same effect with electric heat maintenance tape (like trace heating).

 

[Jon Maine]

Thank you Aidan and MdB, lots of food for thought. Will check out some of those things when my feet touch the floor, although in the mean time I will just monitor as other things have taken my attention.

 

[Penners]

You can achieve the same effect with electric heat maintenance tape (like trace heating).

Aidan, please could you just explain that a bit more, for the benefit of a non-plumber? I'm guessing that electric heat maintenance tape prevents hot water from cooling down over a long pipe run, but what's trace heating?

 

[Jon Maine]

Can be used along pipe runs in cold places to stop freezing and also under a lead valley to prevent snow build up too.

Have not personally used but is good stuff for the tasks mentioned above although I have heard of someones water tank with similar protection against freezing catching the whole roof on fire!!

 

[Penners]

I have heard of someones water tank with similar protection against freezing catching the whole roof on fire!!

Well, fair do's. At least it didn't freeze.

 

[Jon Maine]

I have heard of someones water tank with similar protection against freezing catching the whole roof on fire!!

Well, fair do's. At least it didn't freeze.

Yes just a tad to warm!, I got a £20,000 contract for a scaffolding temporary roof out of it so it helped finance work on the Merchants House!

 

[Aidan]

I'm guessing that electric heat maintenance tape prevents hot water from cooling down over a long pipe run, but what's trace heating?

http://www.tycothermal.com/uk/english/heat_tracing/

Electric self-regulating tape stuff nowadays. The heat maintenance tape regulates it's own temperature. It's used on some commercial installations to avoid the need for a HWS circulating loop. I've never seen it used on domestic pipework; the legionella legislation is in the Health & Safety at Work Act, so it doesn't apply to domestic installations; the legal necessity to control legionella isn't there.
Trace heating is usually installed under the insulation of external pipes to stop them freezing. It used to involve a copper capilliary tube which was heated by steam, fixed to the pipes.

 

[Penners]

Understood. Thanks, Aidan.

 

[Jon Maine]

I have still not got to the bottom of this yet, have been trying to track down a pressure loss in one of my heating systems, looks like I have found it today, a weepy joint in one of the ground source heat pumps.

I hope we see an end to all of these teething troubles soon, I am exhausted!!