Considering s-plan conversion

[dormermike]

Hello

I currently have an open vented Y plan (honeywell) system and the three port valve is not working properly - electrics, motor etc all fine, but when the DHW demand is on, the central heating flow gets hot and some rads warm slightly, depending on how much DHW is needed (i.e. how long its on for). Since we put the heating on yesterday, conversely the DHW gets heating when it doesnt need it, and seems to be causing the hot water to get very hot - not good.

Either way, the valve needs replacement I guess.

As the house (actually converted bungalow) is fairly large, i'd like to zone off the heating at some point: office, airing cupboard, front bedroom, downstairs, downstairs bathroom etc.

For that reason I am considering replacing the 3 port with x2 2 port valves and converting the system to a S Plan. I realise i will need extra controllers etc for the remainder of the conversion.

Looking for feedback on whether this is a good idea or not - am doing it for convenience - current system does do what i want. For example i work from home, would be nice to heat office without heating whole building.

Current setup is:
Ideal mexico super 2 125 boiler (floor stander, 36kw)
699 controller for DHW (heating channel currently unused)
wireless stat for heating
Vented/F&E on 1st floor.
15 rads - some large eg living room is 2.8 metres double vector.

I "get" the plumbing side of it, and accessibility to the 3 port is reasonably ok:

Untitled

• dormermike
• 20 Aug 2011
• 4

Not sure about the wiring yet, but dont think its anything beyond my capability.

Any opinions appreciated - many thanks.

Mike

 

[D_Hailsham]

I currently have an open vented Y plan (honeywell) system and the three port valve is not working properly.

Has it always been like this, or is it a new fault?

If always there, it's a wiring error; if new either the valve is sticking or the actuator (metal box part) is faulty.

Sticking valves can usually be freed and replacement actuators obtained.

i'd like to zone off the heating at some point: office, airing cupboard, front bedroom, downstairs, downstairs bathroom etc.

That may require running new pipes to ensure independence of the two heating zones. Looking at your pic, the HW is the left branch from the valve and the CH the right one, which then splits in two (up and down) so you could treat these as the two CH zones - assuming that's what you want.

 

[dormermike]

I currently have an open vented Y plan (honeywell) system and the three port valve is not working properly.

Has it always been like this, or is it a new fault?

If always there, it's a wiring error; if new either the valve is sticking or the actuator (metal box part) is faulty.

Sticking valves can usually be freed and replacement actuators obtained.

i'd like to zone off the heating at some point: office, airing cupboard, front bedroom, downstairs, downstairs bathroom etc.

That may require running new pipes to ensure independence of the two heating zones. Looking at your pic, the HW is the left branch from the valve and the CH the right one, which then splits in two (up and down) so you could treat these as the two CH zones - assuming that's what you want.

I am not sure if its every worked properly tbh, not since we've lived here (over two years). I will check the wiring, as thats a very good point indeed!!

Also will check the actuator etc, must admit i was working on the assumption that the valve guts were probably coked up or something, and not "sealing" properly so the hot water was bypassing. It is worse when the heating is on though, so i wonder about the wiring now you mention it.

Regarding the zones, yes initially I was thinking of just x2 two port valves located pretty much where the 3 port is at the moment. Under the landing floor, outside of this room (approx 1m away) is where the manifold is, i assume, as the floor gets warm in one 30cmx30cm ish spot when the heating is on. I'll get the floor boards up at some point, and it was from here I was later going to route the 10mm pipework into the airing cupboard to add additional "zones" for the heating circuit.. may be better to run new pipe of course, but i would cross that bridge when i get to it.

I guess my question was also aimed at determining if the boiler is "ok" with zoning, and if a bypass is needed - there is already a rad acting as a bypass, so i guess that would be fine for when all zone valves closed...

 

[D_Hailsham]

I am not sure if its every worked properly tbh, not since we've lived here (over two years). I will check the wiring, as thats a very good point indeed!!

It looks like a Honeywell valve. If there is a small bump (half-pea size) on the top of the lid, you're in luck as the actuator can be separated from the brass body.

Remove cover and undo two screws to remove actuator. The valve spindle should turn easily by hand - less than a quarter turn between stops.

You can read how to test the electrical side in How a mid-position valve works

I guess my question was also aimed at determining if the boiler is "ok" with zoning, and if a bypass is needed - there is already a rad acting as a bypass, so i guess that would be fine for when all zone valves closed...

It's a 30kW boiler, so should be more than adequate. It does require a bypass, though a permanently open rad is not the most efficient way.

 

[twgas]

where is your "by-pass rad" connected, the flow for it would normally be between the pump and motorised vave.

Regarding the zones, yes initially I was thinking of just x2 two port valves located pretty much where the 3 port is at the moment. Under the landing floor, outside of this room (approx 1m away) is where the manifold is, i assume, as the floor gets warm in one 30cmx30cm ish spot when the heating is on. I'll get the floor boards up at some point, and it was from here I was later going to route the 10mm pipework into the airing cupboard to add additional "zones" for the heating circuit.. may be better to run new pipe of course, but i would cross that bridge when i get to it.

this isn't how you would usually zone your heating.

 

[D_Hailsham]

where is your "by-pass rad" connected, the flow for it would normally be between the pump and motorised valve.

Look at the pic - it's not there! I suspect it is either the bathroom rad or the one without a TRV near the room thermostat. In which case a separate ABV will be required.

 

[dormermike]

where is your "by-pass rad" connected, the flow for it would normally be between the pump and motorised valve.

Look at the pic - it's not there! I suspect it is either the bathroom rad or the one without a TRV near the room thermostat. In which case a separate ABV will be required.

Thats correct..

That pic is inside a cupboard inside an "airing room" or whatever it is called - that brown thing on the right of the pic is a door, and to the right of frame there is a rad which I think is the bypass rad - its small and always on when the heating is on (but never hot water - is that right) - i once closed that rad not knowing what it was, and the system kettled like crazy. So i figured it must be the bypass rad.

Can that rad be replaced with a bypass valve - i guess it would operate like a TRV, save heating the rad when not needed etc..

 

[D_Hailsham]

there is a rad which I think is the bypass rad - its small and always on when the heating is on (but never hot water - is that right)

Can that rad be replaced with a bypass valve - i guess it would operate like a TRV, save heating the rad when not needed etc.

That rad would not be suitable as a bypass because it only operates when the heating is on, i.e it comes after the motorized valve. An auto bypass valve connects flow to return, with the flow connection between the pump and any motorized valve.

 

[dormermike]

there is a rad which I think is the bypass rad - its small and always on when the heating is on (but never hot water - is that right)

Can that rad be replaced with a bypass valve - i guess it would operate like a TRV, save heating the rad when not needed etc.

That rad would not be suitable as a bypass because it only operates when the heating is on, i.e it comes after the motorized valve. An auto bypass valve connects flow to return, with the flow connection between the pump and any motorized valve.

Ah i see, yes that makes sense.

I took the actuator off the valve this evening - the spindle was very tight, couldn't move it by hand. I used some transco releasing fluid and a pair of pliers to gentle get it going. A bit of TLC later and it could easily be moved by hand with a nice rubbery bump stop at either end of the travel.

I used a bit of WD40 type stuff then and put it all back to together.

Surprised the motor was strong enough to turn it!

Thanks everyone - hopefully i've freed it off enough to last a while.