Understanding c-plan in new house.

[MarkT1978]

Hi all

Recently moved into a new place which has a c-plan heating system that doesn't appear to have been updated or touched for decades.... no TRVs on rads for example. My aim is to try and add some automation/zoning to it - wifi trvs and openhab controller etc.

Most of it seems to be bordering on normal as far as my limited knowledge of c-plan goes but there's a couple of things I wanted to query.

There is a stat next to the timer with a range of -15 to 10. I'm assuming that as the boiler is in a cupboard in a utility room with no heating that this is some kind of frost protection stat and basically forms a logical OR circuit with the hot water stat.

Secondly, i was trying to identify what kind of 2 port valve this is... can't see any markings on it anywhere.

Its got 5 wires... white yellow orange blue and green/yellow so I believe it is switching the boiler on hot water demand from the stat (it's wired into a block along with the stat). Looks older than me.

Any pointers on those two things would be greatly appreciated.

Cheers

 

[ianmcd]

yes that is a frost stat, the valve is a satchwell 2 port but your pipe looks 22mm if it is then you do not have a C plan as you say, a C plan will use minimum 28mm pipe

 

[MarkT1978]

but your pipe looks 22mm if it is then you do not have a C plan as you say, a C plan will use minimum 28mm pipe

Thanks for that. I guess then that it's some kind of bastardised plan and i'll need to map out exactly what is going on. All i do know so far is...

Oil fired boiler (worcester danesmore 15/19 with pump next to it.)
2 port zone valve at the bottom of the cylinder coil and what appears to be a 15mm tee off on the boiler return pipe after the zone valve.
Tap/shower water upstairs runs through a pump
When room stat calls for heat and timer has CH on, pump runs, boiler doesn't fire
Boiler only seems to fire when timer has HW ON and cylinder stat calls for heat.

I'm seriously considering just getting someone into replace the whole lot cos im not confident that it is going to be as simple as just draining the system, putting TRVs on some rads and then filling it up again.

 

[ianmcd]

Show us some pics of what you have, Pump set up programmer, any thermostats and HW cylinder

 

[MarkT1978]

Heres the best i could do really. Hopefully this gives some indication of what is going on

https://imgur.com/a/ZnTo0jw

 

[oilhead]

It is probably best to budget for a new system such as y plan, with TRV's and room and cylinder stats. The Programmer wiring is not as complex as you may think, as this programmer incorporates the junction box. You don't necessarily need a new boiler as the Danesmoor is pretty well bombproof and all the parts are replaceable. Replumbing the system now can be done before you decide on any redecoration.

 

[MarkT1978]

Thanks Oilhead, especially for the headsup on not really needing a new boiler. Something does need to change around the TRVs for sure. Researching more it seems like this is actually some kind of S-Plan but with only one two-port valve, unless there is one I cant find somewhere.

 

[ianmcd]

switch the HW off and the CH on with the room thermostat turned right down, the boiler and pump should not be running, turn the thermostat up and see if the pump starts immediatelty, if there is a short pause and then it starts then you do indeed have another zone valve somewhere

 

[MarkT1978]

in that instance. the pump starts with no delay at all. Boiler does not come on, pump pumps around cold water.

In order for the boiler to come on and the pump to move hot water around the rads i need the hot water on too (both on programmer and demand from cylinder stat)

Strangely though, when there is a demand for hot water only, the pump does not come on. Boiler does, pump doesnt. This, to me, sounds inherently wrong... hows the water from the boiler getting to cylinder coil to heat it... through convection? It must work cos we do have hot water.

 

[ianmcd]

sounds a complete messup you would be better starting from scratch and get proper controls set up, if you say where you are someone on here might be happy to quote or recommend someone that covers your area

 

[dilalio]

It must work cos we do have hot water.

Your immersion heater's not on is it?

 

[MarkT1978]

Your immersion heater's not on is it?

Haha no.... well the switch is off but I guess that doesn't necessarily mean a thing based on what else i've seen in this setup