Tmv on secondary return pipework

[sheff paul]

Looking at a refurb job with limited space for fitting tmv under each basin,Architect speced tmv in cylinder cupboard,but the HW is on a pumped secondary.Didnt think you could have a Tmv on the secondary pipework...

 

[ShaunCorbs]

No as you still have unmixed hot water bypassing the tmv unless you mix the sr hot I don't see a point

 

[sheff paul]

No as you still have unmixed hot water bypassing the tmv unless you mix the sr hot I don't see a point

The Tmv is drawn on top of the unvented cylinder and the secondary feeds back into the incoming cold back into the cylinder

 

[ShaunCorbs]

The Tmv is drawn on top of the unvented cylinder and the secondary feeds back into the incoming cold back into the cylinder

Sorry miss read thought he wanted the tmv on the sr, the only issue I can see if there are any outlets far away the water might not be upto temp at the far outlets so you might have to up it at tmv so then the close outlets become over temp

 

[stani]

Is the Tmv for all the outlets

 

[sheff paul]

yes its for all outlets, only about 15 metres to the furthest outlet,secondary speced as the taps are only low flow rate so wait is minimal for HW

 

[stani]

I'm pretty sure there is a maximum distance from outlet to Tmv and I think it's a lot less than 15 metres

 

[sheff paul]

I'm pretty sure there is a maximum distance from outlet to Tmv and I think it's a lot less than 15 metres

Gonna check it out mate,i think your right,not sure it needs tmv fitted as it is low risk,and the disabled toilets have tmv type mixers anyway

 

[ShaunCorbs]

I'm pretty sure there is a maximum distance from outlet to Tmv and I think it's a lot less than 15 metres

Isn't it somthing like under 2m ?

 

[stani]

BEAMA are the scheme people now, quick look says for group water that you need to have the mixed temp at the outlet in less than 30 seconds, I presume then that with a secondary return this would be achievable

 

[stani]

Course next problem is temp running round under 45oC there is legionella risk factor, which is why they were originally fitted very close to the outlet.

 

[sheff paul]

so having a TMV on top of the unvented feeding all the outlets, and being returned back to the cylinder

 

[ShaunCorbs]

so having a TMV on top of the unvented feeding all the outlets, and being returned back to the cylinder

What about legionella of the pipwork to the outlets

 

[sheff paul]

might bin the tmv,and have HW running round the secondary at cylinder temp,Doc m toilets are sorted anyway,and advise responsible person about fitting hazard signs 'Hot water'

 

[stani]

Use the legionella card, always helps for them to make a decision

 

[Dotty]

Loop the secondary before the tmv. Perfectly acceptable.

 

[Dotty]

Just read that again. Do away with the tmv altogether. Install secondary as usual. Install thermostatic mixer tap at basin.

Chin the idiotic architect.

Inta - Sequential Thermostatic Basin Mixer Taps

 

[sheff paul]

Just read that again. Do away with the tmv altogether. Install secondary as usual. Install thermostatic mixer tap at basin.

Chin the idiotic architect.

Inta - Sequential Thermostatic Basin Mixer Taps

Cheers Croppie,the developer is a 'cheap skate' think cheap plastic basins,spring loaded taps, but it is a rave club so probably be vandalised on the first night,but do like them mixer taps though might spec em on the next job...

 

[Sparkgap]

The abandoned Energy Saving Trust Best Practice Specification recommends a maximum dead leg volume of 1.5 litres or 10m of 15mm copper pipe. Similar figures have been suggested in the USA (EPA, 2008). If a standard 1.7 litre/minute spray fitting and a maximum wait of 30 seconds is assumed this gives a maximum dead leg volume of 0.85 litres or 5.9m of 15mm pipe.

 

[oz-plumber]

Whatever you do - do it to the Regs.

If there was a legionella outbreak - all fingers will be pointed at you.
The owner, developer, architect, builder and so on will plead ignorance.

Legionella can kill and you would be held accountable.