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 

solar water temp

This topic originated from the How to page called Planning a shower
Click here to return to the page called Planning a shower.

 
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
boatie

from United Kingdom

Joined: 12 May 2004
Posts: 10
Location: United Kingdom

PostPosted: Wed May 12, 2004 5:54 pm Reply with quote

I'm installing a solar system in an off grid house and would like to limit the temp through the taps without resorting to a pricy thermostatic or automated valve (as there is no mains power).
I just need one temperature limiting device for the whole system ideally. Any ideas?

Thanks

Ben
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.
PaulAH

from United Kingdom

Joined: 28 Mar 2004
Posts: 473
Location: United Kingdom
Thanked: 1 time

PostPosted: Wed May 12, 2004 9:38 pm Reply with quote

Not wishing to discourage but.... What is this solar heating system you have that, in the UK, can push the HW temperature up to a point where it needs limiting?
Back to top
 Alert Moderators
boatie

from United Kingdom

Joined: 12 May 2004
Posts: 10
Location: United Kingdom

PostPosted: Sat Jun 12, 2004 12:32 pm Reply with quote

Hmmm, another unbeliever!

The water inside a panel can in certain situations reach 200 degrees and flash to steam, so temperature can certainly be a problem. Practically speaking it reaches around 60 degrees fairly easily, and as the problem I'm trying to solve is in an off grid house with no boiler/mains electric/mains water I wanted to avoid using a powered mixer valve.

Can anyone help?

Ben
Back to top
 Alert Moderators
oilman

from United Kingdom

Joined: 16 Sep 2003
Posts: 7965
Location: United Kingdom
Thanked: 26 times

PostPosted: Sat Jun 12, 2004 1:15 pm Reply with quote

You can use a thermostatic mixer valve used in many combi boilers, but you will need a cold supply to mix it with. If you have a 200 litre tank, to get the temperature to 60 degs, you must have some pretty big panels.

I'm an unbeliever too, I've had 1/2 litre up to 75 Celcius, with a 1 sq m reflector, and it took an hour in bright sunshine. When the coluds covered the sun, that was that.
Back to top
 Alert Moderators
croydoncorgi

from United Kingdom

Joined: 06 Jun 2004
Posts: 4024
Location: London,
United Kingdom
Thanked: 333 times

PostPosted: Mon Jun 14, 2004 7:24 am Reply with quote

You identified a different problem yourself.... if the temperature of the collector exceeds boiling point (of whatever fluid you're using) that's a serious problem in itself.

I'm no expert but I'd have thought you'd need a heatsink arrangement to dump excess heat once the water is hot enough.

Also, it sounds like you're planning a single circuit, with tap water flowing through the collector. Otherside you'll presumably need a circulating pump to move water from a hot water cylinder up to the collector (gravity won't work unless the hot water tank is ABOVE the collector!). If you do use a single circuit, there are (insurmountable?) Water Byelaw issues and anyway the collector will get limescaled and lose efficiency within months. icon_confused.gif
Back to top
 Alert Moderators
boatie

from United Kingdom

Joined: 12 May 2004
Posts: 10
Location: United Kingdom

PostPosted: Sat Jun 19, 2004 8:41 am Reply with quote

OK, thanks for your help...

When I said that they can reach 200 deg and flash to steam I only meant theoretically in a worst case scenario with no safety measures...that would be a pressurised system left to stagnate ie: the pump broke and water was failing to circulate to the tank and nothing in place to relieve the temp/pressure. I certainly won't be doing that...The system will stop working at 60 degrees, but this is still too hot when the elderly/children may be accessing the taps. I guess I will have to only have a feed from the tank and not from the solar circuit directly.

For the unbelievers, 60 deg is definitely possible, even on a cloudy day with a single panel.

The system I will be using is powered by a variable solar pump, ( the tank will be lower than the panel ) but as the house will be run on 12volts I imagined that it would be difficult to source a powered mixer valve. Are thermostatic valves the only solution? I have only seen very expensive ones, but could I source one from the inside of a combi boiler going to scrap?

thanks again
Back to top
 Alert Moderators
oilman

from United Kingdom

Joined: 16 Sep 2003
Posts: 7965
Location: United Kingdom
Thanked: 26 times

PostPosted: Sat Jun 19, 2004 2:26 pm Reply with quote

Quote:
........could I source one from the inside of a combi boiler going to scrap?


Not a good idea if you are worrying about elderly children using the taps. A new one would cost between 25 and 50 depending what features and size you want.
Back to top
 Alert Moderators
boatie

from United Kingdom

Joined: 12 May 2004
Posts: 10
Location: United Kingdom

PostPosted: Sun Jun 20, 2004 7:21 pm Reply with quote

thanks for your help oilman
Back to top
 Alert Moderators
billy bob

from United Kingdom

Joined: 03 Apr 2004
Posts: 685
Location: United Kingdom
Thanked: 12 times

PostPosted: Thu Jun 24, 2004 7:08 pm Reply with quote

You need a blending valve, these are availiable from any plumbers merchant, they are a manuel valve that you adjust yourself until the desired temp is acheived

What solar system are you using, I fit a lot of solar mainly pressurized systems. but I fail to see how you will control the temp of the cylinder without a controller
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
Page 1 of 1

 
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 
Direct Drain Back Solar Water Heating 6 560 Thu Sep 25, 2008 9:50 am
Solar Water Heating - please advise 8 260 Thu Mar 18, 2010 12:39 pm
solar hot water cylinder - direct and indirect thermostat 3 60 Mon Mar 19, 2012 2:21 pm
DIY solar water heating project - any comments? 6 1520 Mon Jan 07, 2008 12:22 pm
Solar Water Heating 2 40 Sun Mar 04, 2012 1:45 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.