UVC Retrofit: Tundish D2 Discharge Pipe in a Passive House

[TerryE]

We've just bought an OSO SX250 UVC to replace or 2×SunAmp PV for the G3 plumber to fit sometime this next month. I have it sitting in situ in the utility room, though still unconnected, ATM.  (It is really a nice piece of kit:  I was initially planning to put a folding door cupboard in front of it but now that it is in situ, we agree that there is no point as its aesthetics are no worse than any other white goods unit.)  My plumber has done one quick site visit, but I am just getting my ducks in a row and trying to anticipate issues before we finalise his work plan.  

 

The main hassle is the tundish discharge pipe (D2) run because doing a new open external discharge would will be a total PITA because of (i) our MBC 300mm twinwall + ext stone skin, and (ii) not having an unsealed opening screwing up our airtightness.  I was wondering if anyone has used one of the new G3 compliant integral tundish + dry traps  (e.g. this Altechnic one).  This neat piece of kit kills quite a few issues such as maintaining airtightness, and being able to run 22mm copper D2 drain along a wall (which would allow us to snake behind a freezer) direct into Part G compliant branch.

 

@JohnMo, you posted on OSO's.  Do you or anyone else have a view?

 

Edited March 4 by TerryE

[SimonD]

I've used both Hotun and Macalpine self sealing tundishes, but not the Altechnic one. Your plumber should be on top of this as it's nothing unusual for an unvented installation.

[Nickfromwales]

On 04/03/2024 at 17:18, TerryE said:

We've just bought an OSO SX250 UVC to replace or 2×SunAmp PV for the G3 plumber to fit sometime this next month. I have it sitting in situ in the utility room, though still unconnected, ATM.  (It is really a nice piece of kit:  I was initially planning to put a folding door cupboard in front of it but now that it is in situ, we agree that there is no point as its aesthetics are no worse than any other white goods unit.)  My plumber has done one quick site visit, but I am just getting my ducks in a row and trying to anticipate issues before we finalise his work plan.  

 

The main hassle is the tundish discharge pipe (D2) run because doing a new open external discharge would will be a total PITA because of (i) our MBC 300mm twinwall + ext stone skin, and (ii) not having an unsealed opening screwing up our airtightness.  I was wondering if anyone has used one of the new G3 compliant integral tundish + dry traps  (e.g. this Altechnic one).  This neat piece of kit kills quite a few issues such as maintaining airtightness, and being able to run 22mm copper D2 drain along a wall (which would allow us to snake behind a freezer) direct into Part G compliant branch.

 

@JohnMo, you posted on OSO's.  Do you or anyone else have a view?

 

I use the McApline on every install, and all projects are airtight etc. These just go to the soil stack wherever that connection is practically made. 
The G3 regs state the maximum length of the D2, including reductions for 90° bends etc, so you may have to beef that up to 28mm   

[TerryE]

4 hours ago, Nickfromwales said:

The G3 regs state the maximum length of the D2, including reductions for 90° bends etc

 

Thanks Nick. The direct distance UVC to stack is ~3½ m so even with the elbow reductions we are well under the 9m limit for 22mm.

[Duncan62]

On 04/03/2024 at 17:18, TerryE said:

We've just bought an OSO SX250 UVC

 

 

Who did you buy it from please?

I'm after a 300L one this year.

[JanetE]

We got our OSO cylinder from a company called Electrical Deals Direct, based in Weston-super-Mare.  Keen price and excellent service with quick delivery.  We can recommend them. 

Edited March 11 by JanetE
Spelling error

[Nickfromwales]

11 hours ago, Duncan62 said:

 

Who did you buy it from please?

I'm after a 300L one this year.

If it is a generic UVC you are after, then you can also try Trevor at cylinders2go, and mention the forum.

[Duncan62]

58 minutes ago, Nickfromwales said:

If it is a generic UVC you are after, then you can also try Trevor at cylinders2go, and mention the forum.

Thank you, should have said specifically the OSO tank, as it has very low heat loss.

[Nickfromwales]

44 minutes ago, Duncan62 said:

Thank you, should have said specifically the OSO tank, as it has very low heat loss.

Get the stats from Telford too. "Go compare" lol.

 

[Duncan62]

11 hours ago, Nickfromwales said:

Get the stats from Telford too. "Go compare" lol.

 

Ok.

 

They loose double the amount of heat compared to the OSO, on a 300L UVC, 2.32kwh/24hrs vs 1.18kwh/24hrs

 

Telford: https://www.tdlonline.co.uk/Heating/Hot-Water-Cylinders/Telford-Stainless-Cylinders/Telford-Tempest-Cylinders-Heat-Pump-Coil/6134-/Telford-Tempest-300-Litre-with-Heat-Pump-Coil-33sqm-TSMI300HP

 

OSO: https://osohotwater.co.uk/product/delta-coil-dcpp/

[TerryE]

On 12/03/2024 at 08:18, Duncan62 said:

They lose double the amount of heat compared to the OSO

 

The wonders as formed vacuum panel insulation. 🙂

[JohnMo]

On 12/03/2024 at 08:18, Duncan62 said:

They loose double the amount of heat compared to the OSO, on a 300L UVC, 2.32kwh/24hrs vs 1.18kwh/24hrs

The heat loss test basically heats cylinder to 65 degs in a 20 deg room and maintains that temperature for 24 hrs and measures how much energy is required to keep it at 65 degs.

 

But storing water at 45 to 50 your losses become really low. Reducing by around 50% for both cylinders. I would think the biggest difference to cylinder heat loss, is the piping install and insulation which is never mentioned or included in the heat loss figure. 

 

Store at a lower temp and don't worry about it. But some perspective the oso delta geo coil is £1800, my slim line cylinder was £1000. It would take 40 years of savings to make up the cost difference.

[jack]

18 minutes ago, JohnMo said:

Store at a lower temp and don't worry about it.

 

I think we ought to be encouraging larger tanks.

 

They store the same amount of energy at a lower temperature (suits ASHPs) in the colder months, and allow greater usage of diverted PV power when the sun is shining.

[Nickfromwales]

11 hours ago, JohnMo said:

The heat loss test basically heats cylinder to 65 degs in a 20 deg room and maintains that temperature for 24 hrs and measures how much energy is required to keep it at 65 degs.

 

But storing water at 45 to 50 your losses become really low. Reducing by around 50% for both cylinders. I would think the biggest difference to cylinder heat loss, is the piping install and insulation which is never mentioned or included in the heat loss figure. 

 

Store at a lower temp and don't worry about it. But some perspective the oso delta geo coil is £1800, my slim line cylinder was £1000. It would take 40 years of savings to make up the cost difference.

Took the words right off of my keyboard lol. Damn right.

I'd rather put the other £800 into everything else.

[TerryE]

In our case  the UVC is free-standing in a utility room, which is basically a corridor from the hall to the back door with sink, worktops and whitegoods along one side.  The OSO UVC fits in a gap behind the hall door, and is in open view.   Because the room is only about 8m² area inside a passive house, a conventional UVC would be unsightly and would turn it into a hot room.  As for the extra £400 or so, IMO this is a small price to pay to keep Jan happy and maintain harmony in the household.

 

I am fitting a couple of digital thermometers on the tank, so I can use these to tune the Immersion timing.

 

Edited March 15 by TerryE