I want to improve my gravity fed hot water by adding a pump

[picasso]

Hi ron the c plan is normally used to upgrade standard gravity systems by allowing hot water and central heating to be controlled seperately, if you fitted the 6 wire zone valve you will have complete control over the hw/ch, the pump just speeds up the recovery of the hot water cylinder (in your case you need the pump because your changing the cylinder),

the ch pump is switched on by the room stat and the hw pump is switched on by the cylinder stat, there are no back feed issues, the boiler is controlled by the zone valve depending on which stat is calling, I will try and find an explanation of how the zone valve works.

 

[Fastlearner]

Hi Picasso,
I'm looking @ the 'C' plan circuit diagram and i cannot see that there is a specific indicator that the brown of the 6 wire valve needs be energised to complete the CH circuit via the white/orange wires If this is so then i can't understand the backfeed issue.
Fact is ;at this point my brain is 'fried'
Ron

 

[picasso]

Hi ron
your thinking to hard try this

hw demand starts with programmer > cylinder stat> brown wire on 2 port (also starts pump) motor in 2 port opens and connects grey (permanent live) with the orange and boiler fires.

ch demand starts with programmer> room stat>white on valve (also starts pump)white connects with orange and boiler fires,

as you can see it depends on the valve being open or closed which wire energises the orange.

 

[ironman1]

the switching inside the 28mm 2 port seperates the hw from the ch, you will need a relay if you go for the 2x2 port valves and 2 pumps, for ease of plumbing and wiring the c plan is the way to go.

Fitting two 22mm motorised valves to heating/hot water along with two pumps will not require a relay if brown wires off each valve are fed to each respective pump. , will be wired exactly the same as an S plan except pump lives are fed via brown on motor valve instead of orange wire.


I take it the system in question is gravity hot water & pumped heating , the OP wants to install a pump on the primary flow to cylinderalong with a motorised valve , the problem i see is when the hot water is calling & the heating is off circulation will take place around the heating circuit due to the hot water pump running , this is the reason a valve needs to be fitted to the heating circuit eliminating this problem , a single 28 mm two port valve fitted to hot water circuit won't help regards reverse flow , so two valves have to be fitted............................no hard thinking from me , i wire these controls with my eyes shut.

 

[picasso]

your right but if you wire it off the brown the valve wont be open when the pump starts, it wont do the pump any harm but not to sure the zone valve will like opening against the pump pressure.

 

[ironman1]

your right but if you wire it off the brown the valve wont be open when the pump starts, it wont do the pump any harm but not to sure the zone valve will like opening against the pump pressure.

Sorry i edited before you posted...................motorised valve will be just fine , have the heating zone valve wired this way in my own house , no problem in 12 years of service.

 

[picasso]

somewhere in the last four pages I am sure the op said there was 4 pipes to his boiler so the 28mm 2 port would be fine without another 2 port to control the ch, the hard thinking comment was aimed at ron.

 

[ironman1]

somewhere in the last four pages I am sure the op said there was 4 pipes to his boiler so the 28mm 2 port would be fine without another 2 port to control the ch, the hard thinking comment was aimed at ron.

Sorry Picasso i should of worn my glasses ron looked like iron.

Even with seperate flow & returns off boiler to hot water/heating , circualtion will take place around heating sytem when hot water pump is running if zone valve is not fitted to heating circuit , will even be the case if the heat exchanger is 'neutral' (cold feed)

 

[ironman1]

New HW pump would be on lowest setting & balanced by pump gate valves.
.
Ron

I don't agree with reducing water flow via pump valves , this can cause cavitation & air ingress , will also shorten the life of pump..................seen it many many times.

 

[Fastlearner]

hi guys,
Interesting discussion.Unfortunately for me there dosn't appear to be concencus of opinion at this point.Clearly Ironman has some first hand experience on this & i most certainly defer to him.
Equally if i try to follow the 'C' plan circuit diagram, assuming the brown to the 2 port valve(28mm version) is the live feed for the HW system and completes the circuit with orange to the HW pump, the CH appears to be programmer> room stat> white 2 port valve( as above)> orange to CH pump.This diagram does appear to suggest circuit independence.I must stress that i am a complete novice in this regard & am desperately trying to apply my best logic.
Much earlier in this discussion it was suggested that one route should be to connect both pumps via the brown wire.At the time, because i did not intend to fit or understand the significance of a CH zone valve i presumed that both pumps should literally be connected to each other via the brown.Under this condition there clearly would be a backfeed issue.
It seems to me that the whole discussion revolves around the role of the brown wire in the valve and the dependence/or not that the HW & CH circuits have on it.
Ron
Point taken on cavitation Ironman
At some point my understanding of the reasoning for the CH zone valve was to eliminate electrical back feeding.Am i now correct in believing that it is in fact to eliminate water flow conflict?

 

[picasso]

the wiring (from my point of view) is very straight forward but as pointed out by ironman there might be a problem with reverse circulation where the returns are connected at the boiler, if this was my system at home I would fit the second pump and see what happened, if I was fitting for a customer I would upgrade the pipework and fit an s plan, it guarantees no problems as its a well tested system.

 

[ironman1]

Ron , my fingers are hurting now & i've lost the will to live (joke).......................WHY can't you just fit two seperate 22mm motorised valves to heating & hot water? , if the answer is yes then just wire as an S plan as we discussed earlier on here , the only deviation from the wireing diagram would be hot water pump would be fed from brown wire on hot water motor valve & heating pump would be fed from brown wire on heating motor valve.

You had it all sorted in you're previous post.

 

[Fastlearner]

Thanks everybody.It's been an interesting journey for me & a pleasure sharing your ideas.Clearly everyone is keen to move on.Time for me to withdraw to the 'smokeroom'.Many thanks

Ron

 

[ironman1]

Am i now correct in believing that it is in fact to eliminate water flow conflict?

Correct............was only joking Ron , no need for the smoke room , you've come this far....................

 

[IKM]

Ron,

I agree with ironman. Fit 22mm motorised valves to the hot water and heating circuits as per the S-Plan and connect the pump lives to the brown wires of the respective valves.

You will need 28mm to 22 mm couplers to connect the 22mm valve into the 28mm hot water circuit. I was surprised at how much force is required to make a good 28mm compression joint. Watch out for this if space for long wrenches is limited.