Need HELP for school project

Rodney Baxter

6 Holmview Heights
Newtownstewart
Co.Tyrone
Northern Ireland
BT78 4JW

Tel: 02881662302

I am a student a Dundee University studying mechanical engineering and would like your help with one of my projects.

Most storage tanks for heating domestic water are kept in the loft or other inaccessible areas. A person however does not know how much hot water is actually in the tank without being at the tank to look and feel. There is no use for the tank to be full of hot water all the time and therefore an indicator of some sort would be useful to show the hot contents in an accessible place. Also there must be enough water for daily events.

My project is to propose a method of indicating to the householder/user remotely, the state of the hot tank contents. Sketchs must also be shown where appropriate.

Please could you give me any information what so ever on this project or any simple solutions to this.

Your help is much appreicated

Rodney Baxter

Big Ed

I guess I will start off

I will assume this is a pressurized vessel so we will meassure themperature rather then water level ? Do you want to regulate the supply of useable hot water through temperature or volume ? Let me assume volume......A thermister thermometer with a remote meter will do the trick . Have the thermometer measure the tank's temperature 1/3 the way up the storage tank . This will give you a good average. There will be some stacking of temperature in the tank . What I mean is the top of the tank will hold the hottest water . A good auto mix vave on the hot water supply will give you a good steady temperature at the faucet.. As far as storage, the vessel should hold enough water for the largest load for the home. The tub ? A normal mix would be two parts hot to one part cold . Most heaters could only supply 80% of usefull hot water so size the tank for the largest load and neglect the mix. The in comming cold water will temper down the last 20% of hot water . This is a normal hot water tank set up. Do you want to supply different amounts at different times using different tanks or a regulation of needed hot water using temperature . Volume would be the safest way .

PJO

I'm confused...

"there is no use for domestice hot water tanks to be kept full"? Are you talking about a tank for an old heating system, and not domestic hot water?

If some domestic hot water tanks are only partially full, I haven't seen one. I know you folks on the other side of the pond prefer tankless HWH sometimes, but this is a new one on me. Someday I'll get to the "Emerald Isle" and find someone with my same name - maybe a whole pub full of 'em - to have a pint with...and oh yeah-check out your hydronics, too :-)

Maybe other Wallies can help here... PJO

Steamhead

Rodney, this sounds very different

from the systems we use in the States. From your description, it sounds like the hot-water tank is placed at the top of the building and feeds the system by gravity.

I recall reading that gravity-feed tanks were used in isolated water-supply systems (as on farms) years ago, before pressurized tanks became practical. But I've never heard of a separate gravity-feed tank for hot water.

Can you be more specific as to how this system works, in particular how the hot water is generated (heat exchanger, coil in tank or whatever) and the type of building the system supplies?


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Dave Yates (PAH)

thermal stacking / cooling

Rodney,
If you don't maintain the hot water at or above 133 degrees F, you will be setting up a bacteria breeeding environment (legionella). You post sounds like you intend to allow some or all of the tank to cool during off-peak hours? If the tanks are sized properly, then set them to maintain suitable temperatures. If you're looking to add an indication of a tank malfunction, then multiple thermistors (placed at varrying elevations on the tank's surface & under the insulation for direct contact) wired to a remote reader can give the needed information at a glance without having to go up into the loft or attic. They can be limked to phone lines for even more remote readings. Ring, ring "Mrs. O'Gorman (me mother's ancestorial name from County Cork), I see from our computer monitor that your lower element has malfunctioned. May we schedule a service call to effect repairs then?"
Thanks,
Dave Yates

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John@Reliable

Thier is a oil tank gauge made by National Something ? can't find full name now. Anyway a float rides up & down the shaft which triggers reed switchs at different levels.
This unit is powered with 24 volts and has a remote light panel that lights up to show m/t 1/4 1/2 3/4 full , have used in pass with good results,they also made custom sizes.Again this is for oil but is a sealed unit may work w/water? Good Luck!

Rich

Help on the school project

Rodney. Try looking up www.scully.com. They manufacture many types of flow level indicators.They are primarily partroleum field experts. But some of there products may be of some help.Another place you might try is the-fluid master-company. I Have used there products for water level indication,but it may take a bit of inventivness on your part.. Good Luck!

Aidan (UK)

Rodney,

You’ve misunderstood the UK installation practices. In open-vented systems, fed from cisterns in the loft-space, only the cold water storage cistern/tank is in the loft. This is not usual in the US, where most of ‘The Walls’ contributors are from, because the harsh winters would freeze the cistern.

The hot water is produced in an indirectly heated cylindrical vessel, which should always be full of water.

See the diagram at http://www.gasman.fsbusiness.co.uk/system_basics.htm

Your level indicator system would need a sensor, an indicator and possibly an amplifier.

Commercial level sensors usually are ultra-sonic, conductive, capacitative or use a static pressure transducer. Register at www.rswww.com and search for level controls. E-mail me if you want more information.

We’ve got an old system which has a float, connected to a drum with a chain. The drum rotates as the water level varies and the drum rotates a variable resistor. The water level is indicated on a meter in a plant room, 6 floor below. It was installed in 1948 and still works.

j_4

level control/indication

we use a multi float assembly for sump pumps & sewage ejectors...very reliable .... works greatfor water