What is the point of C-plan?

[Lieutenant Scott]

>>>>> When HW is not called for via the cylinder stat or programmer then

I fail to see why someone could go to the trouble of making it so you couldn't.

[John Rumm]

>>>>>>>>>>> When HW is not called for via the cylinder stat or programmer then

Some systems were converted from older designs such as gravity feed - hence you don't always get the choice.

Some modern systems actually work better with HW priority - i.e. using a diversion valve rather than a mid position one. In cases where you have a fast recovery cylinder that is able to absorb heat at the rate the boiler can produce it, (many traditional cylinders can only heat at around 5kW) it can make sense to give it the full output until warm, and then divert back to the heating. Suits places with high hot water demands, and also those with modern condensers running split temperature operation (esp with weather compensation). The the boiler can run a hot preset flow temperature for reheating the cylinder, and a variable flow temperature appropriate for the heating load.

[Roger Mills]

I don't suppose they would do so intentionally. They might still foul it up though!

You wouldn't have the choice *until* you converted to C-Plan - then you would.

All good stuff - but not relevant to C-Plan systems which *still* have gravity HW circuits. What you have discussed is the relative merits of Y-Plan vs W-Plan - both of which are fully pumped.

[Doctor Drivel]

Then get an Intergas combi with only 4 moving parts. No 3-way valve, the DHW works when the pump packs up, A standard B&Q available Grundfos is used. You do not need water in the CH for the DHW to work. The pump does not spin when calling DHW. Unbustable. Ultra reliable.

[Doctor Drivel]

Best to have a direct cylinder - cheaper. Heat it via an external plate heat exchanger - the plate replaces the coil. Then have a bronze pump on the fresh water side pumping into the top of the cylinder from the bottom via the plate. The cylinder can be down-sized by 1/3 as the hot water is dumped at the top of the cylinder. Re-heat is super fast and DHW is available for say basin use within a minute of so from cold. The bigger the boiler the better as all the heat from the boiler is dumped into the cylinder. The bigger the boiler the smaller the cylinder. The boiler may be dumping more heat into the top of the cylinder than what is being draw-off.

Using a cheaper "direct" unvented cylinder an Integas combi can be used to heat the cylinder using a bronze pump. Same again as above in smaller cylinder, etc. Much cheaper, simpler installation taking up less space. I have done the figures.....and a far superior system.

[John Rumm]

Yes that's a fair cop... I will get my coat!

[John Rumm]

So are Integas offering the best kickback this month?

[ARWadsworth]

No, they just have the prettiest pictures in the catalogue.

[Doctor Drivel]

You obviously have never heard of them. Atmos rebadged them and sold in the UK in a small way. They are the best, but limited in flow rate to around 15 litres/min depending on model. They are pushing them big in the UK now under the original Dutch Intergas badge. Want a reliable combi that delivers with outside temp compensation as standard and OpenTherm? Then Intergas cannot be beaten. They are cost effective. They just do not go wrong. Simple robust engineering. The whole of the back panel is the heat exchanger.

They can be open vented using an F&E tank with combined feed & expansion. Then no external pressure relief valve is needed running through wall.

I put two of them in large house One doing CH up and one downstairs. One doing one bathroom and one the other. The DHW was combined using check valves and a small shock arrestor for the two baths. Compared to a large space consuming unvented cylinder and all the zone valve paraphernalia, tat can go wrong, it is very cheap - I have done the figures. Also heating backup in the house as well. Always a winner on cost to install & run and in use.

[Doctor Drivel]

It is best you stick to ferrets.

[John Rumm]

better than sticking to catalogues eh?

[Doctor Drivel]

Ferrets eat them. Stick to DIY leave the real stuff to the pros.

[Lieutenant Scott]

water doesn't, to anyone with an ounce of common sense, this means the problem lies with something which is not common to both.[/quote]

last 15 years.

That's not the end of the world is it?

Did I mention my boiler hasn't been serviced or repaired at all since 1999?

[Lieutenant Scott]

>>>>>

Mine does this very simply, one valve for the hot water, one for the heating. You can't have three choices with a valve with two positions!

What causes the difference in operation between HW only and HW + CH?

[John Rumm]

HW only just first the boiler, but not the pump until the cylinder stat is satisfied. HW+CH runs the pump as well.

> I don't think that anyone would install a C-Plan system from scratch (in

Yup, its entire raison d'être...

[Roger Mills]

>>>>>>>>>>>

All together now - OH YES YOU CAN!! You're forgetting that the pump also comes into the equation, but - in a gravity HW and pumped CH system (which is where C-Plan is used) is only used for the CH. Thus: Boiler on, Valve open, pump off - HW only Boiler on, valve closed, pump on - CH only Boiler on, valve open, pump on - both together

*I* make that *three* - what say *you*?

Presumably your system is fully pumped and is thus not relevant to a discussion about C-Plan.

The PUMP - see above. If you want to understand it, you'll need to study the C-Plan circuit diagram shown in the reference above. The valve's auxiliary change-over switch is the cunning bit to watch. When there is only a CH demand - so that the valve is closed - the programmer/room stat switch the pump and the contacts in the valve switch the boiler.

[Lieutenant Scott]

>>>>>>>>>

Relying on gravity for HW to function - I wouldn't do that. Sounds like something Renault would design - have you seen their cooling systems?

Surely it can be simpler than that. The HW control (and thermostat) turn on the valve. The CH control (and room stat) turn on the pump. The boiler is switched on by the central heating control/stat and the valve.

[ARWadsworth]

>>>>>>>>>>>

I cannot decide if you are obtuse or a wind up.

[Lieutenant Scott]

Just asking a simple question.

[Lieutenant Scott]

divides into three (it was two, but I modified it!) to go through three independent valves. One goes to the heat exchanger in the hot water tank. Another goes to the radiators in the house, the other goes to radiators in the garage (I converted it to a parrot aviary, and electric heating is expensive!).

you have to heat the water when you heat the house (or is it the other way round?). My parents boiler is set up so they have to heat the water when they heat the house. What if the house is too cold, but you aren't planning on taking a bath that day? I know the heat from the tank will eventually seep out into the house, or get used later as hot water, but it seems daft to throw heat into something you don't want right now.

I wouldn't want to waste fuel running a "dump radiator".