Confused C plan gravity system

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Will try my best to explain.
Had a new tank fitted and a 2 port valve put on with new thermostat so i could wire c plan for Honeywell controller.
This evening hot water ran out but boiler not come on.
So i tested with martindale on boiler plug and turned thermostat low and high, power was subsequently supplied to boiler as i raised stat and removed power as i lowered stat. So that part seemed to work. I could also hear 2 port valve opening/closing. I noticed though that rads were also getting warm which should be off. So i turned heating on via honeywell and you could hear the pump operate and water circulate ( which you could not with just hot water on ( even though rads getting warm)

On the tank plumber has put 2 port valve 28mm V4043H1106 on bottom pipe (return) is this correct location or should it be on top pipe? Getting confused, double checked all wiring and that seems fine.

Wired as C plan here with exact same part numbers http://www.free-instruction-manuals.com/pdf/pa_458128.pdf which shows V4043H on top pipe?
Could it be the fact it is a Stainless Steel Vented Cylinder and not compatible with thermostat?
 
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If the valve is opening up and the boiler is firing up when the cylinder thermostat is calling for heat, this is as it should be.

With a 'C Plan' once the boiler has heated the water, it then relies on gravity circulation to transfer it from the boiler to the hot water cylinder, and it would appear that this is not happening for some reason. Perhaps there is an airlock somewhere, preventing this natural circulation taking place.

I have seen working 'C Plans' with the valve fitted on the flow or the return. [It may be on the return because of pipe layout restrictions, for example, there may not be space to fit a valve on the flow without restricting the vent pipe]

The pump will only operate when central heating is required, so your description suggests that is correct too. Because there is not a motorised valve in the heating circuit to close it off completely, it is possible to get some gravity circulation around that too, so it's not unusual for some radiators to get warm when only hot water is selected.

The cylinder must also be equipped with a coil suitable for gravity circulation. Not all are.
 
I will check on tank make/model. It looks same as old copper connection wise with exception of having secondary hot water for my shower. and slightly bigger. Could the 2 port valve being on return also be why a few rads are heating up? I guess as one is my bathroom i will have dry towels in summer too ;) Woke up this morning with hot water and warm rad, so programmer kicking in this morning ok. See what happens tonight.
My boiler is old and has a temp dial on it from off to 5 could it be the thermostat in that preventing it firing although before new tank/programmer it was fine?
Honeywell thermostat on tank set to 60 but it is blinking hot, need a thermometer to take its temp. I guess not being a pressurised system i could loosen the top pipe ( hot out) see if any air escapes?
 
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The valve is just there to stop circulation through the hot water cylinder coil, it won't effect the rads regardless of it being on the flow or return.

If the bathroom radiator is heating up, in the past it was common, especially with solid fuel installations, to have the bathroom radiator connected to the hot water circuit instead of the radiator circuit, so it may have been designed to work that way. Was it like that before the cylinder was changed?

The other radiators may be getting some circulation by gravity, but again they would have been like that before.

As it's working now, if there was an airlock it has cleared, so I would leave well alone. C Plans are notoriously slow to heat up the hot water, so maybe you weren't giving it long enough last night.

If you have a problem again, check that A. The boiler is actually heating up by seeing if the flow pipe from it is hot, and then B. Check at the cylinder to see if the flow pipe to the cylinder coil is also hot.
 
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The bathroom was a bedroom so i don't think that was on water circuit, plus having looked at it, it is definitely on the rad circuit. Last night the boiler just was not firing despite power being supplied by the programmer, i checked this with a martindale.
 
It may have been that the boiler had heated up to the temperature set on its thermostat, and shut down whilst the hot water it produced was circulated around the cylinder. With the slow gravity circulation it can take quite some time before it cools enough for the boiler to fire up again, and this period extends as the temperature of the water at boiler and cylinder get closer together.

If it happens again, check to see if the flow pipe leaving the boiler is hot, if it is, then the boiler is doing its bit, if it's not hot, it isn't.

As I said before, with a C Plan it's not unknown for some radiators to get warm when just the hot water is on. however, if the radiators are heating up now and they weren't before the cylinder was replaced, that would suggest some other changes to the pipework may have been made, and I would suggest that you have a chat with the plumber.
 
Ok I think it is possible that the boiler needs 28mm internal coil and the ss tank has 22mm internal coil. My 28mm pipes hhave been reduced to 22mm to go into tank. So might need to buy boiler sooner rather than later and change to an s plan. Hopefully get a greenstar 30/40 cdi regular boiler will do the trick. For now will leave immersion on too and turn stat on boiler up
 
28mm would certainly get better circulation, 22mm would probably still work (it did this morning) but will be slower. This is because the hot water system is not pumped and relies solely on natural convection to heat the cylinder.

Changing the boiler won't help, unless you intend to convert the system to a Y or S plan at the same time, which you probably would have to, because new boilers seem only designed to work with fully pumped systems anyway.
 
Had a new tank fitted and a 2 port valve put on with new thermostat so i could wire c plan for Honeywell controller.
Which programmer do you have? Is it set to Pumped or Gravity?

This evening hot water ran out but boiler not come on. So i tested with martindale on boiler plug and turned thermostat low and high, power was subsequently supplied to boiler as i raised stat and removed power as i lowered stat. So that part seemed to work. I could also hear 2 port valve opening/closing.
I assume you are talking about the cylinder stat. Did you do the same check with the heating on and room stat high/low?

I noticed though that rads were also getting warm which should be off. So i turned heating on via honeywell and you could hear the pump operate and water circulate ( which you could not with just hot water on ( even though rads getting warm)
Rads warming up could be "reverse circulation" (water travelling though the rads in the wrong direction). You can confirm this by checking which pipe is the hotter on the rads; if it's the opposite way round to when the heating is on, you have reverse circulation. An anti-gravity valve will cure this.

On the tank plumber has put 2 port valve 28mm V4043H1106 on bottom pipe (return) is this correct location or should it be on top pipe?
All depends on where the vent pipe (the one which hangs over the small F&E tank is connected to the pipework. Its important that there is an unobstructed path from the boiler through the vent pipe when the valve is closed.

Wired as C plan here with exact same part numbers http://www.free-instruction-manuals.com/pdf/pa_458128.pdf which shows V4043H on top pipe?
The wiring must be exactly as shown on Page 4, section 1.6 of the link you posted. This includes valve wire colours.

Who ordered the new hot water cylinder? If it was the plumber who installed the cylinder etc, then he should have known that you would need one suitable for a gravity system and is therefore responsible for correcting the error.

Of course, if you ordered the cylinder ...
 
yes convert to another plan, is say the WORCESTER GREENSTAR 30CDI CLASSIC REGULAR BOILER a two pipe system i.e flow return so it would pump it quiker to the tank as opposed to my current boiler 4 pipe only heating pumped. Therefore better recovery
 
I am using a Honeywell Sundial RF² Pack 2 with a V4043H 2 Port Motorised Valve 28mm, and a Honeywell L641A Cylinder Stat wiring is 100% as per link provided will check the "reverse circulation" later
 
Out of interest can you get steel 28mm tanks if so the plumber will be sorting this. Not sure why screwfix list indirect tanks with 22mm though? even these are http://www.telford-group.com/view/stainless-vented/1393
Cylinders with 22mm coils are used on fully pumped systems. If the cylinder is to be used on a hybrid system (gravity HW, pumped heating) the coil needs to be 28mm. You will probably find the the pipes connecting boiler to cylinder are also 28mm.
 
Thousands of systems worked without problem on 22mm gravity circs.
It's the fast recovery cylinders that don't work.
 
Cylinders with 22mm coils are used on fully pumped systems. If the cylinder is to be used on a hybrid system (gravity HW, pumped heating) the coil needs to be 28mm. You will probably find the the pipes connecting boiler to cylinder are also 28mm.
So using the WORCESTER GREENSTAR 30CDI CLASSIC REGULAR BOILER run on s plan , am i right in assuming the hot water will be pumped through tank as both heating and water are pumped helping with fast recovery?(Fully Pumped Open Vented System)
With existing setup only my heating is pumped and hot water is on gravity
 

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