water not getting hot

[daveac]

Hi i have an unvented system . the heating is fine but the hot water was not working , i checked the 3part valve and it was not working so i changed it . but the water is still not getting very hot . could it be the cylinder stat that needs changing ? cheers

 

[seco services]

i checked the 3part valve and it was not working

what do you mean it's not working ?
what did you check ?
a 3 port won't have any power to it on hw call.

 

[daveac]

when you switched the controls form heating only to heating and hot water nothing happend on the valve ( it didnt move) i tried it several times and nothing happend , when i installed the new one you could hear it moving and the hot water pipes got hotter the usual

 

[seco services]

when you switched the controls form heating only to heating and hot water nothing happend on the valve ( it didnt move) i tried it several times and nothing happend ,

poss seized spindle.
or the hw stat was satisfied.

when i installed the new one you could hear it moving and the hot water pipes got hotter the usual

right so whats wrong if the pipes are getting hot and valve moves ?

 

[picasso]

unvented system or unvented cylinder ? if cylinder there should be another 2 port valve after the 3 port, make sure its opening when you call for hot water.

 

[daveac]

the hot water is only warm not hot .

i think it has seized , ive had to free it a few time befor .got sick of doing this so changed it . dont know if the stat was satisfied . the stat is set to 70

 

[seco services]

when you say unvented do you mean unvented cylinder or sealed system ?

 

[daveac]

its an unvented system . it has a tank in the loft that feeds the heating system and a tank that feeds the hot water cyclinder
however it has got a solar system connected to it that is not in use , this has an expansion tank connected to it as well
cylinder is 166 ltrs
max head 10m
immertion 760 co
primary heater service area .501 m2
max pressure of primary heater 3.5 bar
internal surface area
boiler is 1200x450 mm
stat drayton acl , hts3

looking at it im guessing that the stat may be at fault its got to be 10 years old ?

 

[seco services]

its an unvented system . it has a tank in the loft that feeds the heating system and a tank that feeds the hot water cyclinder

thats vented.

what does the cyl stat click at if you turn it up/down ?
on hw only does the boiler run for a while then cut out or will keep running ?

 

[daveac]

cyl stat (on out side of cylinder) dose not click , its very hard to turn .
boiler kicks in then cuts out shortly after

 

[seco services]

remove stat from the strap that holds it to the cylinder and let stat hang loose.
boiler should kick in.
is the surface under the stat clean etc and directly on the copper cylinder ?
did it just happen over night etc that the water was only warm ?

 

[daveac]

No its been going on for a while . ill give that a try and see what happens . thanks for all your help
just removed the stat . behind is copper but its not very warm to touch. ill leave it half an hour and see what happens

 

[daveac]

still nothing . boiler kicks in then off a few seconds later . air lock ?

 

[seco services]

is the top pipe into the side of cylinder hot/warm (flow)?
what about the pipe below it hot warm (return)?
on the flow pipe going into cylinder do you have a bleed vent ?

 

[daveac]

is the top pipe into the side of cylinder hot/warm (flow)?
what about the pipe below it hot warm (return)?
on the flow pipe going into cylinder do you have a bleed vent ?

they were warm but now they are very hot . so it looks like its working with out the stat , no bleed vent . i have reconnected the stat to see if it go's back to the way it was , if so i will change the stat . do you agree with this ?

thank you for all your advice
Dave