Glowworm space saver 38 no hot water only when heating is on

[mvanjaarsveldt]

Hi, wonder if anyone can pass on some advice. I have a glowworm spacesaver 38 boiler. I only have hot water when the heating is on. I cant see any divert valves in the system and the water cylinder doesnt have any controls on it ie: thermostat. What controls the temp in the cylinder? and does the boiler come with a build in diverter which controls the flow between heating and hot water?The misses is getting a bit peed off by only having hot water in a very hot house. Any advice would be appreciated. cheers Mike

 

[45yearsagasman]

Check the fill/expansion tank in loft has water in it.If it has then more than likely you have a blocked cold feed.Boiler stat controls temp and there is no built in diverter valve.

 

[mvanjaarsveldt]

Great will have a look. Thanks. As the pump is ony on the central heating system what controls the flow between the boiler and cylinder for hot water and what determines the temp in the cylinder if the is no stat. (out of interest). Cheers

 

[Hugh Jaleak]

Flow from boiler to cylinder uses gravity. (Hot water is lighter (less dense) than cold water, so the heated water starts to rise from the boiler, displacing the colder water back to the boiler thus circulating.)

Hot water temperature (in cylinder, supplied to taps) is governed by the boiler stat. Modern fully pumped systems utlilise motorised valves and stats to control room and hot water temperatures.

 

[mvanjaarsveldt]

Spot on thank you for explaning!! I have checked the tank in the loft and they all seem to fill nicely from the float valves. I only have water when the heating is on. Could it be that the boiler stat is knackered? Thanks

 

[StevenJames125]

what sort of programmer/timer do you have?? may be wired so you can't have h/w oin its own!

 

[mvanjaarsveldt]

Hi, the timer allows me to switch between hot water and c/heating or both. We have kept in on both even through the summer because the stat in the living room controls the c/heating. We havent changed anything regarding the timer. The cistern in the loft fills nicely and you can feel the cold water entering the cylinder. The flow pipe coming from the boiler is hot but goes cold were it enters the cold cylinder. The return to the boiler is cold. Thanks for everyones advice.

 

[StevenJames125]

ok start again

when you select hot water only at your programmer does the boiler fire up?

 

[mvanjaarsveldt]

when I select hot water only the boiler doesnt fire. When I select both heating and hot water, turn up the stat in the living room the boiler fires. So c/heating seems to work fine. We havent made any changes to any of the controls timers etc.

 

[StevenJames125]

could be a faulty programmer - on the hw side - then not sending power to the boiler when a demand is made

if there are no other controls

do you have a wiring centre anywhere near the boiler/airing cupboard/where the pump is?

 

[mvanjaarsveldt]

I have heard the boiler fire twice this morning for a few mintes. So there seems to be some sort of signal coming through.TThere is no stat on the cylinder I will dig out the wiring diagram to see if anything obvious seems wrong. cheers

 

[StevenJames125]

could be an intermittent fault - the programmer could be dirty (backplate) or relays inside worn/sticking etc - have you got a multimeter/used one before?

 

[mvanjaarsveldt]

Thanks, I have a meter and used it before. Just got the wiring diagram out, I will trace back and see were the signal goes tits up. As the cylinder is cold there should be a demand coming from boiler or timer. Will keep you posted. Thanks

 

[StevenJames125]

OK if you know how to use it:

should be voltage to the boiler L terminal when h/w is on at the programmer

 

[mvanjaarsveldt]

Spot on, thanks for your help