Hi,
I am soon to change my heat only system to combi, a viessmann 200 35kw Combi and I have a few layman questions to ask, I'm interested to know as I think its quite clever to be honest but wary of some pitfall.
1. There is a lot of talk of saving space which is great but what about parts like the pump that circulates my radiators, does that stay or is it integral (or non existent) in the combi now via mains pressure?
2. My system is a gravity fed system so the hot being at mains pressure will be brilliant but does that mean there really are no pumps anywhere, just powered by mains. Currently I have the radiator circulation pump, a shower pump and its all extra areas to fail.
3. I currently have a digital controller that switches the immersion or hot water on at preset times, does this now become redundant taken over by the combi.
I guess it will have its own timer built for CH but hot water is theoretically limitless - which is a bit of a weird thing for someone used to immersions for a lifetime.
My wall thermostat (an old fashioned dial in the hallway), that still must stay.
4. Old System: It looks to me like the gravity tank is fed by mains which feeds the HW cylinder in which water is heated via boiler. The immersion feeds HW to taps via gravity. CH water which is pumped through the boiler then round the system using a pump.
New system the combi directly feeds HW to taps and combi boiler heats and feeds CH using mains pressure. Is that right?
So in effect removing gravity tanks and connecting directly to water feeds for CH/rads which the combi controls.
Like I say it seems very clever and quite simple and I'm wary of these things, although not for the first time have I been wrong that something so simple works so well.
5. Last Q - when the system is drained to fit new boiler then it must be refilled, how or where would that vent now to let trapped air escape, does each rad have to be bled or does the combi have an inbuilt air dispel valve. I imagine once on mains air is forced out much more quickly.
6. Sorry 1 more, is the CH loop a closed loop, so the CH fluid recirculates, I ask because we have a water softener and I was advised that water must not get into the system but the only system that could be is the CH, so it must be closed yes ?
Is there anything else to add to the system, magna clean, fernox etc, I have a magnetic 'thing' on the pipe but happy to add more if they help.
Thanks in advance for replies, great forum.
PG
I am soon to change my heat only system to combi, a viessmann 200 35kw Combi and I have a few layman questions to ask, I'm interested to know as I think its quite clever to be honest but wary of some pitfall.
1. There is a lot of talk of saving space which is great but what about parts like the pump that circulates my radiators, does that stay or is it integral (or non existent) in the combi now via mains pressure?
2. My system is a gravity fed system so the hot being at mains pressure will be brilliant but does that mean there really are no pumps anywhere, just powered by mains. Currently I have the radiator circulation pump, a shower pump and its all extra areas to fail.
3. I currently have a digital controller that switches the immersion or hot water on at preset times, does this now become redundant taken over by the combi.
I guess it will have its own timer built for CH but hot water is theoretically limitless - which is a bit of a weird thing for someone used to immersions for a lifetime.
My wall thermostat (an old fashioned dial in the hallway), that still must stay.
4. Old System: It looks to me like the gravity tank is fed by mains which feeds the HW cylinder in which water is heated via boiler. The immersion feeds HW to taps via gravity. CH water which is pumped through the boiler then round the system using a pump.
New system the combi directly feeds HW to taps and combi boiler heats and feeds CH using mains pressure. Is that right?
So in effect removing gravity tanks and connecting directly to water feeds for CH/rads which the combi controls.
Like I say it seems very clever and quite simple and I'm wary of these things, although not for the first time have I been wrong that something so simple works so well.
5. Last Q - when the system is drained to fit new boiler then it must be refilled, how or where would that vent now to let trapped air escape, does each rad have to be bled or does the combi have an inbuilt air dispel valve. I imagine once on mains air is forced out much more quickly.
6. Sorry 1 more, is the CH loop a closed loop, so the CH fluid recirculates, I ask because we have a water softener and I was advised that water must not get into the system but the only system that could be is the CH, so it must be closed yes ?
Is there anything else to add to the system, magna clean, fernox etc, I have a magnetic 'thing' on the pipe but happy to add more if they help.
Thanks in advance for replies, great forum.
PG
