Power showers

[bernardgreen]

That being the case. The water rate from supply is irrelevant as the tank is the buffer.

If the flow rate to the shower from the cylinder is greater than the flow rate from the supply then the buffer cylinder will become empty of water..

and a big shower pump is what you want eh?

If you suck ( pump ) water out of a unvented cylinder faster than the supply can replenish the cylinder then you could create a situation where a vacuum is created in the cylinder and it crumples inwards. ( or maybe unvented cylinders have safety devices to prevent a vacuum being created, I don't know )

 

[Madrab]

or maybe unvented cylinders have safety devices to prevent a vacuum being created, I don't know

You are able to fit float switches which allow the pump to be shut down if the water level in the Cold Water Storage Cistern (CWSC) drops too low.

It should never get to that though as you would always spec the pump size by considering the size of the CWSC , the size of supply pipe to the HW cylinder, the size of cylinder and the flow of the shower.

 

[bernardgreen]

You are able to fit float switches which allow the pump to be shut down if the water level in the Cold Water Storage Cistern (CWSC) drops too low

That works for a vented hot water cylinder but how would an unvented ( direct on supply ) hot water cylinder be protected from having a vacuum created.

 

[Madrab]

That works for a vented hot water cylinder but how would an unvented ( direct on supply ) hot water cylinder be protected from having a vacuum created.

Apologies Bernard, misread the response, an unvented will only deliver what it can be supplied with, the driving force behind the flow from an unvented cylinder is the mains. You wouldn't ever pump an unvented cylinder, there shouldn't be a need to. If you did and you over pumped then depending on the strength of the pump then I guess it could implode.

 

[muggles]

That works for a vented hot water cylinder but how would an unvented ( direct on supply ) hot water cylinder be protected from having a vacuum created.

By fitting an anti-vacuum valve

 

[muggles]

I assume the dynamic pressure will remain the same once that supply pipe is upgraded from 15 to 32? I believe its 25mm to the boundary then it drops to 15mm from the boundary to my internal stop tap.

Your dynamic pressure should improve. Your static pressure will remain constant

 

[BlueLoo]

I was listening to the interview of the WB boiler chairman yesterday by the Skill Builder bloke.
He uses his 40KW Combi direct for the showers. Just tells his family to not turn the taps on.

I thought that was a bit of a fudge in the MIL house but was surprised to hear a boiler manf chairman have the same thing in his house.
You live and learn....

 

[ianmcd]

I was listening to the interview of the WB boiler chairman yesterday by the Skill Builder bloke.
He uses his 40KW Combi direct for the showers. Just tells his family to not turn the taps on.

I thought that was a bit of a fudge in the MIL house but was surprised to hear a boiler manf chairman have the same thing in his house.
You live and learn....

Glad you think WB chairman,or any other manus chairman for that matter, would know anything about their product, very seldom are these people promoted engineers, they are usually accountants or from a sales background

 

[williamglossop]

Measured my static pressure. Its 60 psi (4 bar) will i see a noticeable improvement in flow within upgrade from 15mm to 32? Think the com pipe is 25 tho. Will this be enough to run an indirect cylinder?

 

[Madrab]

Check dynamic pressure, run the test with 2 or more outlets open.

Your flow will increase as you increase the pipe bore as friction will be reduced, that being said a 15mm pipe can deliver loads of flow as long as the dynamic pressure is sufficient, it just gets noisier than if it was a larger bore pipe.

As suggested, if you are seeing a 2.5 to 3 bar dynamic with at least 15l/Min then you would be within unvented territory. Just ensure it is 22mm all the way to the cylinder and back out to the 1st branching to the HW outlets to maximise flow and minimise noise.

 

[williamglossop]

I tested again today and the static pressure was lower..... no idea why, but it was 50psi/3 Bar static. I left it connected and opened the kitchen tap and bathroom tap at the same time, and the dynamic pressure barely moved.... it stayed around 3 Bar. With a 32mm water pipe upgrade..... at these kind of pressures, will an unvented be feasible and worth it over say an electric shower in the new bathroom?

 

[Madrab]

It will probably have dropped due to district demand, possibly more people using water at the time of the test.

If you are achieving 3 bar dynamic (open a couple of outlets and see what it does, as long as it doesn't drop much below 2.5 bar then your fine) with a min of 15L/Min then that should serve an unvented quite happily, especially with a pipe upgrade.

BTW why are you going to 32mm when the service pipe is 25mm?

 

[williamglossop]

Cost difference between 32 n 25 was negligible..... didnt see a reason not to go for the 32. It probably won't make much difference, but I just thought wtf not.