DIYnot
Local | Network
   DIYnot > Forums
Local | Network
DIYnot Network Local DIYnot Network Local  
  Forum IndexForum Index     RulesRules    HelpHelp     Join FREERegister Free     About CookiesCookies     SearchSearch     LoginLogin 

Unvented below sink water heater- PRV drain

Goto page 1, 2  Next
 
Post new topic   Reply to topic    DIYnot.com Forum Index > Plumbing and Central Heating
Search this topic :: View previous topic :: View next topic  
Author Message
4xpaws

from United Kingdom

Joined: 23 Apr 2007
Posts: 49
Location: United Kingdom
Thanked: 1 time

PostPosted: Sun Aug 05, 2007 10:46 am Reply with quote

I'm having a 'below sink' unvented water heater installed in the loft. It needs a pressure relief valve installed in the pipework along with it. Has the drain coming from the PRV & tundish got to be copper? or can it be PE-X barrier pipe?
Back to top
 Alert Moderators

If you do not want to see this advert, click here to login or if you are new click here to join free.
Doctor Drivel

from United Kingdom

Joined: 08 Jul 2006
Posts: 1079
Location: London,
United Kingdom

PostPosted: Sun Aug 05, 2007 11:01 am Reply with quote

4xpaws wrote:
I'm having a 'below sink' unvented water heater installed in the loft. It needs a pressure relief valve installed in the pipework along with it. Has the drain coming from the PRV & tundish got to be copper? or can it be PE-X barrier pipe?


Avoid these. Fit a heat bank thermal store.
Back to top
 Alert Moderators
4xpaws

from United Kingdom

Joined: 23 Apr 2007
Posts: 49
Location: United Kingdom
Thanked: 1 time

PostPosted: Sun Aug 05, 2007 11:48 am Reply with quote

Thanks for comment.

One reason amongst others is too long a pipe run is needed to fit thermal store. 30m+ run needed. Its for 3rd floor and storage cylinder's in basement.
Back to top
 Alert Moderators
Dan_Robinson

from United Kingdom

Joined: 01 Jul 2007
Posts: 27233
Location: Hertfordshire,
United Kingdom
Thanked: 4250 times

PostPosted: Sun Aug 05, 2007 12:56 pm Reply with quote

What make and model?

I think it would have to be copper.

What are you feeding with it?

Why not fit a secondary return - much lower running costs and less maintenance.
Back to top
 Alert Moderators
4xpaws

from United Kingdom

Joined: 23 Apr 2007
Posts: 49
Location: United Kingdom
Thanked: 1 time

PostPosted: Sun Aug 05, 2007 1:16 pm Reply with quote

Speedlow SF10Li unvented water heater

feed from mains.

Secondary return -what's all that about? Returning to where?
Back to top
 Alert Moderators
jay1

from United Kingdom

Joined: 07 Jan 2007
Posts: 169
Location: London,
United Kingdom
Thanked: 9 times

PostPosted: Sun Aug 05, 2007 1:35 pm Reply with quote

does it need to have prv and tundish if it is storing less than 15 litres, im pretty sure its doesnt need to.
Back to top
 Alert Moderators
Doctor Drivel

from United Kingdom

Joined: 08 Jul 2006
Posts: 1079
Location: London,
United Kingdom

PostPosted: Sun Aug 05, 2007 2:29 pm Reply with quote

4xpaws wrote:
Thanks for comment.

One reason amongst others is too long a pipe run is needed to fit thermal store. 30m+ run needed. Its for 3rd floor and storage cylinder's in basement.


A DHW secondary circulation pump can be fitted to a thermal store heat bank.
Back to top
 Alert Moderators
4xpaws

from United Kingdom

Joined: 23 Apr 2007
Posts: 49
Location: United Kingdom
Thanked: 1 time

PostPosted: Sun Aug 05, 2007 2:37 pm Reply with quote

Comes supplied with PRV + all fitting senarios show the 6 bar PRV installed.
Back to top
 Alert Moderators
Dan_Robinson

from United Kingdom

Joined: 01 Jul 2007
Posts: 27233
Location: Hertfordshire,
United Kingdom
Thanked: 4250 times

PostPosted: Sun Aug 05, 2007 2:39 pm Reply with quote

4xpaws wrote:

Secondary return -what's all that about? Returning to where?


Its basically just a loop going back to the cylinder that re-circulates the hot water using a bronze pump set on a timer/timer & thermostat so that the hot water doesn't take three weeks to get to taps at the opposite end of the house. Hotels use it as do hospitals.


You haven't answered the main quetion of what it's for.


DD the man doesn't need a thermal store; leave it - for a change.
Back to top
 Alert Moderators
Nige F

from United Kingdom

Joined: 28 Jun 2005
Posts: 16115
Location: United Kingdom
Thanked: 797 times

PostPosted: Sun Aug 05, 2007 2:43 pm Reply with quote

jay1 wrote:
does it need to have prv and tundish if it is storing less than 15 litres, im pretty sure its doesnt need to.
Fraid not, they come with a PRV and you have to allow 4 meters of supply 15mm pipe for expansion back up the supply pipe before a draw off on said supply.........or 2 metres of 22mm pipe icon_wink.gif I would run copper and use a 22x35 reducer as a tundish.......in fact I`ve done 2 now ,as they are not covered by unvented certificating icon_wink.gif which I aint got
Back to top
 Alert Moderators
4xpaws

from United Kingdom

Joined: 23 Apr 2007
Posts: 49
Location: United Kingdom
Thanked: 1 time

PostPosted: Sun Aug 05, 2007 2:47 pm Reply with quote

Quote:
A DHW secondary circulation pump can be fitted to a thermal store heat bank.


Pipe run involved means its too costly in terms of labour & materials + access needed to install run is difficult. Forget it.

The heater's bought and now needs fitting (correctly)!
Back to top
 Alert Moderators
Dan_Robinson

from United Kingdom

Joined: 01 Jul 2007
Posts: 27233
Location: Hertfordshire,
United Kingdom
Thanked: 4250 times

PostPosted: Sun Aug 05, 2007 2:49 pm Reply with quote

You are welcome.

icon_rolleyes.gif
Back to top
 Alert Moderators
4xpaws

from United Kingdom

Joined: 23 Apr 2007
Posts: 49
Location: United Kingdom
Thanked: 1 time

PostPosted: Sun Aug 05, 2007 3:22 pm Reply with quote

Quote:

You haven't answered the main quetion of what it's for.


Its to supply a sink in a 3rd floor bathroom. Boiler and cylinder a down in basement. Cold tank is on the 3rd floor too. Previous plumber said the under sink heater was the best option for getting hot water to 3rd floor sink.

Quote:
with a PRV and you have to allow 4 meters of supply 15mm pipe for expansion back up the supply pipe before a draw off on said supply.........or 2 metres of 22mm pipe


-The fitting instructions show at least 2.8m of 15mm pipe is needed for expansion to the nearest cold draw off from the heater. As the curent main supply is 15mm, adding reducers and a section of roughly 1.3m of 22mm between the nearest cold draw off and the 15mm fitting to the heater is acceptable??

Fitting a length of 22mm -would this step up the the size pipework needed for the PRV discharge? Currently with the PRV Tee'd off 15mm supply, discharge pipe D1 (PRV to tundish) is 15mm & D2 (tundish to outside) is 22mm.

With this 22mm 'expansion' section would D1 now become 22mm and D2 28mm??

-Finally, can the PRV drain pipe discharge onto a roof, or has it got to go 3 story's down to a surface drain, or... can it vent into the cold water/ DHW cistern?

I'm a bit bemused you can't use barrier pipe for the drain given that you can use it for other HW CH applications.
Back to top
 Alert Moderators
Dan_Robinson

from United Kingdom

Joined: 01 Jul 2007
Posts: 27233
Location: Hertfordshire,
United Kingdom
Thanked: 4250 times

PostPosted: Sun Aug 05, 2007 3:35 pm Reply with quote

You want to use a 10 litre unvented heater to run a bathroom?

hhhmmmm. Are you sure?

I wouldn't terminate it over the roof unless you had at least three metres of surface before it entered the guttering.

It would be a copper pipe as the PEX pipe might not handle the superheted water/steam that is released under fault conditions.

Hence avoiding the termination of the Safety discharge over the roof.

I don't think you quite understand how all this works do you?

The size of the incoming main has little bearing on what happens after the heater with regards the safety discharge.
Back to top
 Alert Moderators
Balenza

from United Kingdom

Joined: 16 Mar 2007
Posts: 1268
Location: United Kingdom

PostPosted: Sun Aug 05, 2007 4:12 pm Reply with quote

Dan Robinson wrote

Quote:
You want to use a 10 litre unvented heater to run a bathroom?


Sounds like he only wants to provide hot water to a basin. icon_exclaim.gif
Back to top
 Alert Moderators
Search this topic :: View previous topic :: View next topic  
Post new topic   Reply to topic    DIYnot.com Forum Index > Plumbing and Central Heating All times are GMT
Goto page 1, 2  Next
Page 1 of 2

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
Similar Topics   Replies   Views   Posted 
Installing Under Sink Water Heater - Unvented? 4 840 Mon Mar 02, 2009 10:05 pm
OSO unvented water heater bleeding me dry 7 100 Thu Oct 25, 2012 8:19 pm
Unvented water heater concern 7 540 Mon Jan 12, 2009 3:26 pm
Unvented water heater 5 280 Thu Mar 18, 2010 11:40 pm
Santon Premier Unvented Water Heater Problems 10 1760 Fri Dec 04, 2009 9:02 pm


 
DIYnot
Find an Expert | Find a Supplier | Search DIYnot.com
Network | Advertising | Newsletter
DIY | DIY How To | @home | DIY Wiki | DIY Forum
By using this site you agree to our Terms of Service / Disclaimer.
Please read our Privacy Policy. Copyright © 2000-2014 DIYnot Limited.