Adding UFH to Y plan (radiators removed)

[picasso]

Why use an s plan ? get rid of the 3 port and just have a two port controlling the hot water, the op hasn't wired a hot water off so the valve will stay in ch, probably find his boiler has shut down of the overheat stat.

 

[doesitmatter]

Why use an s plan ? get rid of the 3 port and just have a two port controlling the hot water, the op hasn't wired a hot water off so the valve will stay in ch, probably find his boiler has shut down of the overheat stat.

Thanks, I was worried about that but read that without power, the spring will trigger and return the mid position back to HW. If this is not correct, I will look for a different solution with ensures it does.

As for the wiring, to turn on the UFH with separate thermostats connected to a Heatmiser UH8, it appears correct to me as has been working all day now the boiler is now operational. I will check my post to see if I made a mistake with the description.

However, I do not know if it has returned back to HW and for the over-run pump to transfer excess heat to the cylinder, and of course if that's what you mean by it not being wired correctly, you may be correct and I'll report back.

 

[doesitmatter]

They will stay at CH only if that is the last option selected, a position which has the motor powered continuously to waste electricity and shorten the life of the motor. That only lasts until HW is selected again.
Otherwise it will return to HW only.

Y plan is obsolete, and as mentioned above should be replaced with S plan where extra zones or an unvented cylinder is added.
No new system should be installed using Y plan.

Worth noting, that no extra zones have been added and the unvented cylinder was added previously, though of course should have had a 2 port, which would've made life much easier for me!

Your first paragraph confused me a little. You said it only lasts until HW is selected again and then said, 'otherwise it will return to HW only'. To me that reads as contradictory. Could you correct my amateur understanding of the 3 port? I thought once power was severed, which would be the case with a NO port(?), which goes from closed to open when the coil stops getting power, the spring would return the 3 port to HW only?
Should I wire the NC terminal to select HW on the programmer?

 

[doesitmatter]

@flameport
Just read this -
No power to valve - all wires no voltage - Hot Water Only (Port B is opened)
240V on orange- HW only
240V on White & Orange - Hot Water & Heating (open to Port A & B)
240V on White & Grey & Orange - Heating only (open to Port A only)
240V on Grey only - Valve is held in last port of call

This of course means that I have left power on grey only, meaning that the valve is held in last port of call. So thank you for your post.

Should I wire the NC to the HW off?

 

[Madrab]

I get the feeling it's all getting very complicated again. Of course there is no real need to convert to a complete S plan by adding a 2 port onto the UFH circuit as that circuit would ultimately be controlled by the pump/UH8 but using 2x2 ports allows both circuits to be separately controlled/isolated. If there is a 3 port valve then the UV must have a 2 port as a fail safe.

The UH8 could also be used to control the HW 2 port (Rad channel) and therefore centralise the controls. Overrun can easily be managed by a bypass.

A 3 port valve is a notoriously bad design (but very clever) and the actuators constantly burn themselves out after a time and have to be replaced. They are weak points and therefore, as suggested, the system is now considered obsolete

edited for some really bad grammar

 

[Madrab]

Just an addition - good reference and visual description here and how it all runs together and what cable is energised during each function/position

Central Heating

Personal website of John Turnbull. This site reflects my hobbies and interests from a personal point of view rather than a business point of view.

octaveblue.co.uk

 

[doesitmatter]

Thanks, @Madrab. In all honesty, I don't share your complexity concerns but then I am coming from it from the, 'I already have a 3 port valve installed, it's all working and all I need to do is ensure it defaults to HW' camp. Also, I'm not looking at it compared to an S plan, which I definitely understand is the better & simpler system and I expect to move to when needed, ie-3 port stops working, or I get the solar guy back to stick in the 2 port.
Also, I like learning and 'complicated' means research

Fwiw, I did some testing and as other said, the 3 port does hold at CH when the call for heat ends. However, it did not appear that the motor was running when all was turned off. There was neither vibration, nor noise. Next time I turn the CH off, I'll turn off the 3 port power to see if it gears back to HW.

 

[Madrab]

That's fair enough, if you see it as a learning exercise, mid position valves can be a bit of a headache given the way it uses it's extra cabling and the resistor/diode to covert to DC current to 'idle' the valve.

This is another great explanation I use and shows the valves internals and how the valve does it's job then and should answer your question as to how to get the valve back to HW (B)

How the 3-port valve works

This site features Arduino projects and modifying the Triumph TR7 and other classic cars as well as other DIY projects

mr-r.co.uk

 

[doesitmatter]

Thank you so much, you've been so helpful and as you might have expected, I will be trying to get the S plan on the go now the solar guy came back and, without admitting fault, said a 2 port is used as a safety 'feature'. so if I can't find anyone, he will try and fit me in to fit one.
How to say....'I effed up', without admitting you effed up! I would do it myself but I don't want to touch the unvented cylinder connection, plus as it's a tight space and I haven't got a blow torch, I'd prefer some soldered joints.
I'll be ensuring a bypass valve is included too!

I'll report back when all sorted, perhaps with some pictures but you've kept a new born warm, @Madrab, plus a new mum calmer, so I really am hugely grateful!

 

[Madrab]

That's what we're all here for @doesitmatter , if we can help then the 'job's a guddun'

 

[doesitmatter]

As I am moving to an S plan, I thought I'd ask about automatic bypass valves, as there's a lot of info out there but the question I had, hasn't been answered.
I've worked out a solution (image below) to include one which comes between, rather than before all zone valve piping (it's easier for me to install that way) but is it going to cause me issues and I should install it directly before any zone valve branching and as the last 'return' before the boiler?

 

[Madrab]

The bypass needs to be after the pump and before the valves, in that diagram it is still 'before' the valves by the looks of it. Basically you need to be able to have a path to the valve and then back to the return that can't be blocked by either valve.

 

[doesitmatter]

Thanks, it is 'before' the valves but not before the pipework leading to the valves. Plus, the distance to the valves from that pipework is 20cm at most. It joins up with the CH return at the bottom of a T, which meets the cylinder 20cm above.

Knowing I can do it the way I suggest is a great help and hopefully helps others, as I have seen people prioritise orders of return connections.

Thanks....again!!!

 

[Madrab]

Yes ... the normal golden rule is the last return on a mixed cylinder and radiator system should be cylinder to avoid reverse circulation but that's normally with radiators. With you not having radiators and it being UFH that's on a valved and pumped circuit, then that shouldn't be an issue.