Upgrading W to Y Plan

[wotsisname]

Hi,
Appreciate if someone out there can advise.
I plan to upgrade the heating from the W plan to Y.
Does anyone know if the brass component of the three-port valve is the same on both types of diverter.
I'm was hoping to fit the 4073 actuator without replacing the actual 4044 valve to save draining the system.
Thanks,
Francis

 

[D_Hailsham]

What make is the valve?

 

[wotsisname]

It is a Honeywell V4044 with 40003916-002 power head.

 

[kirkgas]

i cant help with the compatability but i have cracking W, Y & S plan A4 diagrams if you want them, they are actually part of a fully functioning power point which show poweg going through each component with every click, quite good in an anorak kinda way, if you want the diagrams PM me (same goes for anyone else)

 

[D_Hailsham]

It is a Honeywell V4044 with 40003916-002 power head.

In that case the body is identical, you just have to change the head, which is part no: 40003916-003

Before you rush out and buy a new head, can I ask why you want to change from W plan to Y plan?

 

[wotsisname]

Hi D_Hailsham,
Thanks for the info. That makes things simpler.

Actually I have not yet looked in detail at the Y plan and would welcome suggestions.

The problem with this W plan is CH cannot work independently of HW and HW is given priority. In this house there is a comprehensive room programmer/thermostat allowing the CW to be on all time, with temp depending on time of day and day of week. And set to frost-free temp while away recently. But the HW has to be up to temperature for the heating to come on. So HW has to be on 24x7 when it is only needed a couple of hours a day. To achieve this the owner has to fiddle with the HW thermostat with a screw driver deep into airing cupboard to set target HW temp to minimum.

I hope that makes sense.

I have assumed the Y plan will alow independence between CH and HW but have not yet looked at it in detail. When investigating the system and discovered it was W plan, a couple of sites rather dismissed it and suggested it is often converted to the Y plan - no plumbing changes compared to S plan.

Better ideas or any advice would be much appreciated.

Thanks

 

[twgas]

You should be able to have heating without HW, I would suspect your programmer is the item that needs looking at, pos just a dip switch on the back!

 

[D_Hailsham]

The problem with this W plan is CH cannot work independently of HW and HW is given priority.

That's true of all W Plan systems, it's HW priority. This is also true of combi boilers and many weather compensation systems.

Which make/model boiler do you have?

Which make/model Programmer/Thermostat do you have?

I have assumed the Y plan will allow independence between CH and HW but have not yet looked at it in detail.

It would, but you need to find out why you have W Plan. The boiler and control info will help.

 

[wotsisname]

HW thermostat is L641A1039
CH Thermostat/Programmer is Grasslin ECO ET2 Digital Thermostat
Boiler is Potterton Prima 50B
No timer or programmer overall or for HW

 

[twgas]

do you have a time control for the HW, I think the r/stat only does the CH - correct me if I'm wrong.

 

[D_Hailsham]

HW thermostat is L641A1039
CH Thermostat/Programmer is Grasslin ECO ET2 Digital Thermostat
Boiler is Potterton Prima 50B
No timer or programmer overall or for HW

There's nothing special about those components to require a W Plan.

The ET2 only controls the heating side (time and temperature) and the L641A controls the HW side (temperature only). You should be able to get heating on its own, when HW does not take priority, so there must be a wiring fault which means you can't get CH without HW.

 

[wotsisname]

I think the limitation must be the simple 3-port valve which has to be one or tother and not both.

This is what I've found out (or I think I've found out) for this installation:

When power switch is on, power goes permanently to boiler, COM of HW stat and COM of room stat.

When HW stat calls for heat, power goes to switched boiler feed, then on to pump from boiler and power is off to the 3-port valve.

When HW no longer calls for heat, then power goes to the 3-port valve so it is always powered and switched over for CH when HW does not call for heat, regardless of whether room stat calls for heat.

When room stat calls for heat, it switches power to switched boiler feed and on to the pump. The normally-on connection from room stat is not used. But at this point if HW is also calling for heat then power to diverter valve is removed so hot water goes only to HW.

This is one of the pieces of information from http://www.diyfaq.org.uk/plumbing/controls/controls.html

"W-plan systems can leave you without CH for some time since they can provide heat to only one of HW or CH at any given moment. Usually HW is given priority, so if you run a bath all heat will be diverted to the HW for as long as it takes to reheat the water. If several people have fresh baths or showers (particularly power showers) in succession you may be without CH for an hour or more. This effect can be reduced by fitting a fast recovery cylinder (which has a more efficient heat exchanger and therefore heats up much quicker). People have been known to be so dissatisfied with a W-plan installation that they have had it converted to Y-plan."

(Mick, As you suggest, there is no timer on HW and the room stat is purely CH.)

I really appreciate your efforts to help me sort this out.

Thanks,
Francis

 

[D_Hailsham]

When power switch is on, power goes permanently to boiler, COM of HW stat and COM of room stat.

OK, so far!

When HW stat calls for heat, power goes to switched boiler feed, then on to pump from boiler and power is off to the 3-port valve.

That's OK

When HW no longer calls for heat, then power goes to the 3-port valve so it is always powered and switched over for CH when HW does not call for heat, regardless of whether room stat calls for heat.

That's also correct but it means the valve can be powered unnecessarily for very long times, i,e when HW is not required.

When room stat calls for heat, it switches power to switched boiler feed and on to the pump. The normally-on connection from room stat is not used.

The first part is OK, but what do you mean by the bit in bold?

But at this point if HW is also calling for heat then power to diverter valve is removed so hot water goes only to HW.

That's right.

 

[wotsisname]

Sorry, I should have said Normally Closed i.e. the connection that would be powered by the room stat when not calling for heat.

 

[wotsisname]

I can now see wiring faults. For example HW stat Common is the power-in from mains switch as opposed to going out to the switched boiler feed. This is part of the reason diverter is always powered when HW stat is not calling for heat.

All the wiring needs to be reviewed against the W plan diagram. But already I can see that with the correct wiring HW can be totally off and CH work independently. So I can install a timer for the HW.

W plan will be adequate here.

Thanks for your help and making me think. I had too quickly concluded W plan useless given my erroneous thought that CH was totally dependent on HW being on and up to temp as it is here

A statement in the Honeywell documentation still puzzles me though. "Time Control: Should be one which does not allow heating to be selected without hot water." Can't see why that's a requirement. Suspect I've missed something. I'll look at it all again in the morning and probably draw different conclusions.

Cheers, Francis

(PS kirkgas, I'd appreciate your powerpoints but don't know how to PM you. Think we need to be friends.)