Surrey Dave
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| posted on 20/10/10 at 11:20 PM |
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Controlling Hot Water Temp In Conventional CH
Help!
My parents have a conventional heating system with an oil fired floorstanding boiler, there is no progammer,they just turn it on and of as
neccesary!!!
The hot water tank is indirect and permanently in the flow of the primary pipes,so the only control of water temp is to turn the boiler up or down.
The water is being heated longer than neccesary and is generally too hot.
So can I fit a mid position 3port valve? and a tank stat to the existing setup with a pipe bypassing the tank without bothering with a programmer.
Or I'm guessing another option could be under sink thermosts, any other remedies.
Locost as possible of course.
[Edited on 20/10/10 by Surrey Dave]
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cliftyhanger
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| posted on 21/10/10 at 07:01 AM |
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not a real expert but...the tank stat sends a signal to the programmer, and that controls the 3 port valve.
Why not fit a programmer/roomstat/tank stat with the 3 port valve. The controller is the easiest bit. Ubless I have missed something.
I am guessing it is a fully pumped system?
*edit* actually, it may be all gravity if no controls at all.....
[Edited on 21/10/10 by cliftyhanger]
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tegwin
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| posted on 21/10/10 at 10:02 AM |
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I would fit a tank stat so that when the water cyl gets to whatever temp it shuts the boiler off... Not useful if the CH is running though..
Have you thought about adding a thermostatic mixer valve on the outlet of the tank? So the hot water gets blended with a set amount of cold water
before going to the hot taps... means you can set the water temp to the taps to whatever you like... and because its not standing at that temp for
long you can safely run water temps of 30 degrees if you want...
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Would the last person who leaves the country please switch off the lights and close the door!
www.verticalhorizonsmedia.tv
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spewing
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| posted on 21/10/10 at 03:43 PM |
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Without seeing what your parents have got i cant tell but they could have a semi gravity system. The hot water is heated by gravity circulation
through the boiler when the boiler is hot and the central heating has a pump to pump water through the raidiators.
The easiest way to tell is how many pipes are leaving the boiler. This system is usually two 28mm pipes leaving the boiler from one side and two 22mm
pipes leaving from the other with a pump somewhere in the 22mm circuit.
Depending on the system design once the pump is on the majority of the heat goes to the raidiators.
The simplest way to control this would be a 2 port valve in the return from the cylinder controlled through a cylinder thermostat. While your at it
you may as well fit a time switch to control the heating as well and switch the boiler to prevent it cycling.
Have a look at this
http://www.home-heating-systems-and-solutions.com/central-heating-design.html#cplan.
If your parents have a semi gravity system this would control the system with the minimum alteration to the existing plumbing.
Certainly not the most efficient way to control the system but probably the cheapest to retro fit. Also dont put anything in the system that can block
a vent pipe or a feed pipe from the feed and expansion tank.
Kev
[Edited on 21/10/10 by spewing]
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Surrey Dave
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| posted on 21/10/10 at 04:40 PM |
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TMV ?
quote:
Originally posted by tegwin
I would fit a tank stat so that when the water cyl gets to whatever temp it shuts the boiler off... Not useful if the CH is running though..
Have you thought about adding a thermostatic mixer valve on the outlet of the tank? So the hot water gets blended with a set amount of cold water
before going to the hot taps... means you can set the water temp to the taps to whatever you like... and because its not standing at that temp for
long you can safely run water temps of 30 degrees if you want...
Yes I was looking at the thermostatic mixer valves, and I did wonder if I could fit one on the HW tank outlet, is this an OK thing to do? its fairly
easy to do and would make the water temperature safe everywhere.
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tegwin
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| posted on 21/10/10 at 06:16 PM |
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Its the "done thing" in some places...
You obviously cant store the water at less than 60 degrees because of legionaires.... But you dont want to give your guests burns from the hot
water... So you mix hot and cold on the tank outlet before piping it to the bathrooms at a more sensible temp..
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Would the last person who leaves the country please switch off the lights and close the door!
www.verticalhorizonsmedia.tv
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Surrey Dave
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| posted on 22/10/10 at 01:55 PM |
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There is a room stat that has a cover on it but when I trace the wires back and test it, it appears to only stop the pump not the whole boiler.
Can I fit a thermostat in series with the current on off switch for the boiler, which would then control the whole boiler.
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spewing
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| posted on 22/10/10 at 10:09 PM |
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quote:
Originally posted by Surrey Dave
There is a room stat that has a cover on it but when I trace the wires back and test it, it appears to only stop the pump not the whole boiler.
Can I fit a thermostat in series with the current on off switch for the boiler, which would then control the whole boiler.
You can fit a cylinder thermostat to switch off the boiler but that take out the heating as well.
Sounds like at present the boiler thermostat is controlling everything and to get the water temperature down you will have to turn that down.
The heating will still work at a lower temperature but the transfer of energy from the rads to the air is more efficent at a higher rad temperature.
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