Dual heating control - honeywell 2 and 3 port valves

[sparkingwing]

I have a haeting system in an old farmhouse where downstairs is new underfloor heating and upstairs on standard Y plan rads and hot water.
A 2 Honeywell port valve has been added in front of the 3 port valve to shut off when no heat is required for y plan but heat is required for underfloor manifold (fed from same pipework from boiler). To wire controls I am planning on wiring the two control panels (y plan and underfloor controller) in parallel to the pump and boiler so either can call for heat. To prevent unwanted heat to the Y plan when underfloor is calling I plan on wiring the orange wire(pump L) from the 3 port valve to the Brown wire of the 2 port valve which will open 2 port when called, and then orange wire out of 2 port to pump/boiler. Does anyone think there will be a problem with this being wired in parallel with the underfloor controller and would there be any problems from live back feed when underfloor switches boiler and Y plan doesn't? Sorry for long question but didn't want to go straight for relay options if not needed. Comments welcomed, thanks.

 

[ericmark]

Not sure why you are using multi valves? However saying that, I have, but back to basic first, each radiator has a TRV and the head decides when and how much flow is required to heat the room at the time set.

The underfloor heating controller is full of relays and these work the valves on the manifold for the floor, a three position three port valve, or for that matter any non wifi connected motorised valve has a problem as often only one micro switch, so it is not down to the turning on/off of the valve, but the turning of the central heating boiler on/off or up/down which is the problem.

So again back to basic, an oil boiler in the main turns on/off, a gas boiler in the main turns up/down, so controls for oil are not the same as controls for gas. In the main we do not want valves like this for gas, as in the main we want to gradually turn the flow up or down, so the boiler can respond by also turning up or down, OK to turn the supply on/off to a hot coil for the DHW tank, but in the main, we want analogue control.

The C Plan and the Y Plan have an advantage over the S Plan with oil boilers, as oil boilers do tend to be on/off, and when they switch off, there is often no cool down sequence, so having a valve which leaves the hot coil connected with not power to a motorised valve, means the boiler can cool by heating the DHW.

I use this type of motorised valve, as the house has a garage converted into a flat, and I want to be able to turn the whole flats heating off. The main house I have 9 programmable TRV heads, so each room is independent.

However no room can heat if boiler is not running, best option is linked TRV heads, but my TRV heads don't link to the hub yet, so I have selected two areas, in my case hall and living room, and wall thermostats in either room can turn the boiler on. Reason for two, is living room also has an open fire, so if that's in use it would cause rest of house to get cold, and hall cools slower than living room, so using just that thermostat living room, unless fire lit, can get cold.

So you it seems are doing the same to make sure boiler runs when required. But no room should heat up unless the TRV calls for heat, so why fit a general motorised valve?

In hind sight I made an error fitting motorised valves, as the micro switches can stick, which means boiler and more to point, pump running, with a closed valve.

Since my pump on return, the idea of a by-pass valve does not work, if pump was on feed, then by-pass valve will open, and so pump not pushing against a closed valve, and water flowing through boiler.

 

[sparkingwing]

TO confirm, yes it is an oil boiler and yes the underfloor is controller by its own mixing set and heatmiser control panel which operates the valves for the 9 underfloor zones. However boiler supply in feeds both underfloor mixing set and y plan for hot water and upstairs rads so twin port valve just isolates the y plan when underfloor mixer calls for heat and y plan doesn't . Both y plan controller and heatmiser control plan can switch on boiler and supply pump.

 

[ericmark]

Both y plan controller and heatmiser control plan can switch on boiler and supply pump.

Hope all three can turn on boiler, tank thermostat, Y Plan and Heatmiser. Y Plan

is not the best design. White from room stat, grey from tank stat, but grey is line to stop DHW heating not to make it heat. It makes the motor drive the valve all the way, if DHW not wanted.

So

A 2 Honeywell port valve has been added in front of the 3 port valve to shut off when no heat is required for y plan but heat is required for underfloor manifold (fed from same pipework from boiler).

should that not be after the three port valve, is in front will also stop DHW? You will as it stands need relays, as you need to have three feeds to boiler, but these must not back feed, I have the same problem. I had to sit down and draw it all out.

and after all that, still got it wrong. It should have two relays, only used one. So house can run without the flat, but the flat can't run without the house, however don't need latter so not corrected. Also today doubled up on house thermostat, have Nest and Wiser working now, but only Nest Gen 3 does DHW.