vented pumped system

[tommyl18]

Hi guys not to sure what system im dealing with here ?

Its a vented system got a feed and expansion tank in the loft. It has a back boiler and off the back boiler is a pump there are no zone valves or 3 port valves . there is a programmable thermostat which only has timer for the central heating not the hot water. The cylinder is indirect with no cylinder stat or immersion heater so im a bit confused on how the hot water is controlled ?

 

[picasso]

you have a gravity hot water/pumped central heating system, the hot water temp is controlled by the boiler stat, they dont come much more basic than this.

 

[tommyl18]

so if ive got this right then there should be a primary flow and return off the boiler to the cylinder and a secondary flow and return to the pump for the central heating

 

[picasso]

depends on the bbu, some have four tappings for as you said gravity primary flow and return and pumped flow and return, others have two tappings with the gravity primarys rising to the cylinder with the pumped central heating tapped off the flow and the return teeing in before the boiler,

There should be a timer for hot water only/ hot water and central heating, you cant have central heating on its own, who installed your programmable room stat?

 

[tommyl18]

the stat was already in the house its just got settings for turning the central heating on and off, you can set the time it comes on and for how long for but there is nothing at all on it for hot water

 

[picasso]

in that case your going to have to fit a timer or you wont be able to have hot water without the heating on as well.

something like this...//www.diynot.com/shop/Honeywell_ST699B_24_Hour_Electonic_Programmer/151789

 

[tommyl18]

im not sure how the programmer is wired up but would the room stat not switch the pump off when the temperature is satisfied and the timer switch off the boiler

 

[picasso]

there is a programmable thermostat which only has timer for the central heating not the hot water.

you didint say you had a seperate timer is any thing else you want to add?

 

[tommyl18]

im not sure what the difference is I do apologise ill explain whats here there is a room stat on the stairs and then there is a control unit in the living room where you can turn the central heating on and off and also set times on it to turn on and off but there is nothing on the control unit about hot water

 

[picasso]

sounds like somebody has removed the timer for your system,(are you sure there isint one hidden away somewhere?) you will need to fit one otherwise you will have no hot water when you switch off the central heating, look at the link I posted before.

 

[TicklyT]

The timer controls both the heating and hot water times, and the room 'stat overrides the heating control once the heating demand is satisfied, leaving the boiler just heating hot water until the internal boiler thermostat is satisfied, or the timer switches it off.

To run hot water without heating, turn the room stat to minimum, and the timer on. You cannot run the heating without hot water.

A slightly more sophisticated variation uses a 2-channel programmer in place of the simple timer and adjusting the room 'stat, but it has the same limited heating/hot water permutations. There is usually an interlock within the programmer making it impossible to select heating without hot water.

 

[picasso]

To run hot water without heating, turn the room stat to minimum, and the timer on. You cannot run the heating without hot water.

.

the op is saying he hasnt got a timer, just a programmable room stat with no setting for hot water, it looks as if the room stat is controlling the boiler and pump but the "installer" hasnt considered the hot water.

 

[TicklyT]

The OP did say

.......there is a control unit in the living room where you can turn the central heating on and off and also set times on it to turn on and off .......

 

[picasso]

once again I havent read the replies properly my apologies