How to automate the oil burner with the thermal store

[jcmode]

Hello,
I have a 500 litre thermal store for the underfloor heating and a 500 litre tank for the domestic hot water along with an oil burner in the shed 30 metres away.
I have an old style manual timer to switch the oil burner on and off and another timer to start the thermal store for the ufh.
How can I automate this so that the oil burner turns off when the thermal store reaches the desired temperature.
Oh yes, what should the desired temp be.

[KenB]

jcmode,

For under £15 you can buy a "tank-stat".   Some models can be also used as pipe-stats.  You have a long strap of spring wire (like old curtain spring) which allows you to strap it around the top of the tank such that the metal back of the stat is in good metallic contact with the metal of the tank.

They normally have a rotary dial that allows you to set the turn off temperature and a normally closed and normally open pair of contacts.

When the stat gets up to temperature it will open a pair of contacts and you wire these in series with the timer contacts it will turn off the oil burner.

If your tank is heavily insulated you can either cut an aperture in the insulation to fit the stat - or you can get adjustable stats with capillary  probe like sensors that can be located into a thermopocket.  I  got one of these for about £15 from Farnell Electronics, also RS Components - see this link.

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=6618284



Ken

[jcmode]

Hello KenB
Thanks for your reply. I will look into it immediately.
John

[Solal]

30m is a long way off  for  the DHW  store! Is this  an unvented cylinder?
If no secondary return loop is fitted  you will  have a long wait at the  taps before  HW is delivered.
DHW  is generally stored at  about 60c.


The buffer  tank  temperature   for the ufh  needs  only to be heated to a maximum  of  50c. Then no mixing valves are needed.
But the boiler thermostat then  needs to be set at a maximum  of 50c! But thats no use when HW needed.

So you need  to either consider the use of mixing valves to reduce the temperature  to the underfloor  heating or weather compensation  control  to reheat  the  buffer store.

BUT.. if your oil boiler  is  non condensing model  then a minimum  return temperature specified  may be  55c or above.

[jcmode]

Thanks for the information Solal.

Actually the non condensing oil burner is 30m away in the outside shed. The DHW tank and UFH buffer tank are beside each other in the utility room in the house and they are linked. I have a delsol meter on the wall which gives the temperature in each tank along with the tubes on the roof.
The oil burner switches off when it reaches 50c , but I want it to switch off when the tanks reach their prescribed temperature. Any suggestions

[dhaslam]

When you say the tanks are linked  do you mean that they are  heated together  but  separate  draw offs?    This would mean that   the boiler  cannot go off until the bottom of each  tank is up to temperature.   Two    thermostats would probably work in parallel, either one being able to turn on the boiler if the temperature is below the required setting.    A pipe stat on  the return from each  cylinder would probably  work OK.   They don't give very accurate readings but you could fine tune the temperature with the  existing thermometers.  The boiler setting would need to be higher than the other settings.         

[Brandon]

plumb them as an s-plan then they can be controlled seperately to the desired temperatures...