Y-Plan heating and "Last Port of Call" issue with 3-port valve

[elsmandino]

Afternoon all.

I have recently come across an apparent "downside" of Y-Plan heating systems, whereby the valve can be held in position, even when no heating or hot water is required.

In my ignorance, I have never noticed this, despite having lived in my house for well over ten years.

I realise that the motors are designed to handle the heat and the electricity to hold the valve, other than in the B position, is insignificant.

However, I was just wondering when does this happen and how can I recreate it?

 

[Echo the husky]

The valve will stay in its last position when the programmer/stat is switched off however if both HW and CH are running and the valve is in the mid position and shut off together the valve will spring return to HW only. If only the CH is running the valve will stay powered and remain in the CH position, as it is kept powered from the HW off connection of the programmer.

To recreate, switch on CH only until boiler fires, then turn CH off. The valve will remain powered until HW is switched on.

 

[stem]

There's a great description of how it works here.

In the summer if the central heating isn't being used then the valve will sit permanently unpowered in the hot water only position.

 

[Johntheo5]

One might think that it will remain unpowered at least overnight by programming the HW only on for a few minutes last thing at night but this will only work if the cylinder stat is also calling for cylinder heating. Attached is a modification that ensures it will only be powered when CH only (or CH+HW) is calling, the Unmodified schematic is also attached.

 

[Echo the husky]

That modification would certainly increase the life of the synchron motor as well as save some electric.

 

[DP]

That modification would certainly increase the life of the synchron motor as well as save some electric.

On the other hand, adding more complexity to what many find difficult plan to wire
While y plan is not difficult to wire up, look at the queries, you would think it is rocket science

 

[Johntheo5]

On the other hand, adding more complexity to what many find difficult plan to wire
While y plan is not difficult to wire up, look at the queries, you would think it is rocket science

It may not require science to wire it but it does require a reasonably good knowledge of how this truly ingenious device works, especially when trouble shooting it. It requires both the programmer "HW OFF" contacts and the cylinder "Satisfied Contacts" to supply 230V otherwise the valve will never move to the CH only position, the HW OFF contacts are required if CH only is required and the cylinder Satisfied contacts are required if both CH&HW are requested but the cylinder stat is satisfied, the mid position is achieved by changing AC to DC and using this as a electric pair of brake shoes as like poles attract, then, to avoid the motor poles becoming permanently magnetized a very small de magnetizing AC current is supplied with CH only on. Maybe just a small touch of electrical (rocket?) science.

 

[Exedon]

On the other hand, adding more complexity to what many find difficult plan to wire
While y plan is not difficult to wire up, look at the queries, you would think it is rocket science

See way more wiring problems with Y plan than anything else.
Almost seems to be standard to use 3 core for cylinder stat and not mark green and yellow as a carrier.
For the fairly minimal cost of another zone valve in real terms could never see point in doing Y plan.

 

[DP]

4 core, 5 and 6 core is stock item in the van as is stranded specified cable. Non of this cable that would carry the load for a small village or solid core T&E some favour. If three port wiring is too much science for someone, my suggestion is sit down and learn about it.

Some one who struggles with wiring of a three port valve, what else do they struggle with when it comes to fault finding in a boiler or control systems

 

[elsmandino]

Thanks so much for all this - extremely helpful.

I agree that the Y Plan really is a great example of lateral thinking to (I presume) save costs.

To recreate, switch on CH only until boiler fires, then turn CH off. The valve will remain powered until HW is switched on.

I did exactly this and the valve did indeed stay in the A position. I cannot believe that I had not noticed this before - my central heating (in the winter) will always go off after my boiler, so I will have had this position every night for weeks on end.

One might think that it will remain unpowered at least overnight by programming the HW only on for a few minutes last thing at night but this will only work if the cylinder stat is also calling for cylinder heating.

I can now completely see why this approach will not work, now.

That extra relay hack is really very clever and something I might now do. Is this something that could theoretically be done or do many add this to their Y Plan in practice?

 

[DP]

to avoid the motor poles becoming permanently magnetized a very small de magnetizing AC current is supplied with CH

John, what is the source of this information.

The motor runs due to multiple poles and AC voltage. The locking voltage is DC that would be like dropping an anchor not forgetting circuit run current would burn the motor if it locked in place, so is softened by adding high resistance to hold the motor in place with acceptable heat dissipation. These motors are not for prolonged powered use. Sunvic ( I am sure you are familiar with this brand) introduced MOMO drive which now I understand has been modified to be interchangeable with spring return mechanism 2 port valve

2 port valves, you will agree have no drive cut circuit but are held in open position by virtue of stalled motor against the stop as does three port valve or diverter for that matter in CH port open only

 

[Harry Bloomfield]

Afternoon all.

I have recently come across an apparent "downside" of Y-Plan heating systems, whereby the valve can be held in position, even when no heating or hot water is required.

In my ignorance, I have never noticed this, despite having lived in my house for well over ten years.

I realise that the motors are designed to handle the heat and the electricity to hold the valve, other than in the B position, is insignificant.

However, I was just wondering when does this happen and how can I recreate it?

A MOMO actuator, avoids that, and I would suggest they are much more reliable for it, though more susceptible to water damage. Electrically, they are a direct swap for a spring return Y plan actuator, though the water valve needs to be swapped along with the actuator.

MOMO types, only run the motor, when a change in valve position is required, the rest of the time, the motor is unpowered. Rather than fighting against a spring, the actuator/valve, rotates the full 360 degrees, to the called position. They also save around 5w that is wasted by a normal actuator, when called for CH, or CH+HW.

I went through a whole series of standard 3-port actuators over the years, motor failures, microswitch failures, and the actuators simply jamming due to the grease hardening. I have not suffered a single issue so far, with the MOMO type.

 

[elsmandino]

Great - exactly what I need (i.e. a MOMO actuator).

I would prefer to not go down the DIY route, if possible - as mentioned, this might cause some confusion for subsequent purchasers of the house.

I have got through a number of valves over the years and this shall hopefully help put a stop to this.

Am I correct in thinking that this valve is my only option?

Sunvic Momo Valve 22mm 3 Port SDMV2304

The diverter valve is a part that only appears in combi boilers. It allows the hot water to be directed to the central heating system (radiators, etc.) or to the hot water system (taps, etc.). This feature is one of the mains reasons combi boilers are a p

www.cityplumbing.co.uk

I cannot seem to find any competitors.

 

[Harry Bloomfield]

Am I correct in thinking that this valve is my only option?

Sunvic Momo Valve 22mm 3 Port SDMV2304

The diverter valve is a part that only appears in combi boilers. It allows the hot water to be directed to the central heating system (radiators, etc.) or to the hot water system (taps, etc.). This feature is one of the mains reasons combi boilers are a p

www.cityplumbing.co.uk

I don't know about the only option, but it is the very same one I fitted to my system. You can get them much cheaper than that, have a look on ebay. The red wheel rotates, to indicate which valve position it is set to.

There are a few mentions of it being susceptible to water damage, if mounted in any other position than actuator head, uppermost.

Out of stock, but much cheaper - £55 https://bhl.co.uk/sunvic-sdmv2304-motorised-mid-position-valve-22mm-8912304-w302200.html

 

[DP]

Great - exactly what I need (i.e. a MOMO actuator).

I would prefer to not go down the DIY route, if possible - as mentioned, this might cause some confusion for subsequent purchasers of the house.

I have got through a number of valves over the years and this shall hopefully help put a stop to this.

Am I correct in thinking that this valve is my only option?

Sunvic Momo Valve 22mm 3 Port SDMV2304

The diverter valve is a part that only appears in combi boilers. It allows the hot water to be directed to the central heating system (radiators, etc.) or to the hot water system (taps, etc.). This feature is one of the mains reasons combi boilers are a p

www.cityplumbing.co.uk

I cannot seem to find any competitors.

Stick with what you have. Keep a spare one in stock if you are worried
The valve body is just as fickle as any other brand, no better and no worst
The syncron motors- there are cheap motors on the market, I found these did not last long.
Drayton or Honeywell packaged ones seem to be more reliable