does my central heating pump have to be on to heat the HW?

[00db]

I have a part gravity part pump system, does the CH pump have to be on for my HW tank to heat up?

I have seen several explainations saying the tank being heated by convection. diagrams show a coil inside the tank which is part of the CH system. Does the CH pump therefore circulate hot water through this coil which then by convection heats the water in the tank to give Hot Water?

Therefore the CH pump must be on to get Hot Water?

 

[Rob]

No HW is by convection. Pump kicks in only when Ch is needed.

 

[wiggikins]

Depends on system you have, do you have a 3-way valve , two 2-port valves or neither???

 

[00db]

i dont have any valves in the system.

Could you give me a brief explaination of how convection works?

 

[wiggikins]

LOOOK IT UP!!

 

[seco services]

heat rises you have gravity hw so pump doesn't come in

 

[Rob]

Hot water is less dense so as its heated it rises. The cold water falls towards the boiler and circulation occurs.

Not very efficient but quite reliable.

 

[00db]

great, thanks. a nice simple explaination! I did look it up but the explainations I found were either incorrect or over complex.

 

[D_Hailsham]

I have a part gravity part pump system, does the CH pump have to be on for my HW tank to heat up?

I have seen several explainations saying the tank being heated by convection. diagrams show a coil inside the tank which is part of the CH system. Does the CH pump therefore circulate hot water through this coil which then by convection heats the water in the tank to give Hot Water?

Therefore the CH pump must be on to get Hot Water?

Why are you asking?
Does your pump run, even when you are only heating the hot water?

 

[00db]

the two channel programmer I have put in lets me switch off the CH pump while still having the boiler on for HW.

I just wanted to know if the HW would still heat up with the CH pump off.

 

[D_Hailsham]

the two channel programmer I have put in lets me switch off the CH pump while still having the boiler on for HW.

I just wanted to know if the HW would still heat up with the CH pump off.

Does the programmer have a switch on the back which you can set to gravity? If so, it should be on that setting if you have a gravity HW/pumped CH system.

You say you have no valves in the system. Nothing like either of these?

 

[00db]

hi. yes there is a jumper on the back which you are supposed to remove if using on a fully pumped system.

nope, don't have either of those valves on the system.

 

[D_Hailsham]

hi. yes there is a jumper on the back which you are supposed to remove if using on a fully pumped system.

nope, don't have either of those valves on the system.

It would be worthwhile considering upgrading your gravity HW/pumped CH system to a fully pumped one as the gravity method of heating the water is not very efficient and you do not have independent control over the HW temp, it is determined by the boiler temp.

The alternative is the C-plan. This is still gravity HW but has a valve in the HW circuit controlled by a thermostat on the HW cylinder. This means that the HW temperature is independent of the boiler temp, so you can have the boiler temp set to 80C and the HW temp set to 60C

Have a look at Sundial C plan

 

[00db]

ill check it out, thanks. anything to save costs on the old gas bill!