Heating System Upgrades Advice

[djruk]

Hi all

My house has a Baxi Solo WM RS conventional boiler dating back to about 1990. In terms of controls, there is an external SwitchMaster 400 mechanical controller, which probably dating back to the original boiler install. The controls are very crude and allow for water or heat/water only - no independant heating or program options. The controller is wired to an ACL room thermostat, which is also ancient looking. In the airing cupboard we have a 'Grundfos Selectric' pump and a Drayton 3 port mid position MA-1 valve. The tank has a Danfoss thermostat attached.

Everything works as it stands, but I am looking at the options to bring the system into the 21st century. The boiler is working, so this can stay put. I've checked with Baxi and the boiler just needs a switched mains fed live (240v) so the guy suggested the controller upgrade is an easy route given the mid-position valve already in place. I'd like a modern programmable timer and stat with independent heat/water control. Not really very clued up on the better systems and don't mind whether wired/wireless. So I'd appreciate any advice or recommendations on the upgrade path.

I can provide pics on any aspect of the system if it would help.

Thanks in advance.

 

[djruk]

Here are some pics:

View media item 83745
View media item 83746
View media item 83747
View media item 83749
View media item 83750
View media item 83751
View media item 83752
View media item 83753
View media item 83754

 

[D_Hailsham]

It seems a bit strange that you have a mid-position valve and cylinder stat yet you can only have CH on if the HW is also on. It suggests that there is something missing in the wiring.

The cable from the mid-pos valve probably goes into a junction box. Could you remove the lid from the box (power off first) and find the terminal to which the grey valve wire is connected. If there are two other wires, i.e. a total of 3 wires, connected to this terminal, you are OK. But if there's only one other wire (total 2 wires) which goes to the cylinder stat), you will need to alter the wiring.

If there three wires (total) then the Honeywell Sundial RF² Pack 2 Wireless Enabled Programmer and Thermostat is probably your best bet.

This is a two channel programmer, which should be able to go where the existing Switchmaster is located, and a wireless thermostat.

But if only a total of two wires, it will depend on how easy it is to run a new wire from junction box to the Switchmaster location.

Might be best to sort this out first.

 

[djruk]

Thanks for your reply D_Hailsham

I've taken some pics and inspected the junction box wiring as you requested. Here are my findings:


Junction box connector connections

Left hand connections go to Pump, MPV and Tank Stat.
Right hand connections go to 4x (not 3!) grey sheathed multi core cables behind wall.

LEFT RIGHT

1 - empty ----------------------- 1 - empty

2 - ORANGE (MPV) ------------- 2 - YELLOW (CABLE 1)
- BROWN (pump)
- BLACK (stat)

3 - empty ------------------------ 3 - BLACK (CABLE 4)

4 - YELLOW (stat) --------------- 4 - empty
- GREY (MPV)

5 - RED (stat) -------------------- 5 - YELLOW (CABLE 3)

6 - WHITE (MPV) ---------------- 6 - YELLOW (CABLE 2)

7 - empty ------------------------ 7 - 2x RED (CABLE 2 & 3)

8 - GRN/YEL (pump) ------------ 8 - 4x GRN/YEL (CABLE 1,2,3 & 4)
- GRN/YEL (MPV)

9 - BLUE (pump) ---------------- 9 - 3x BLUE (CABLE 1,2 & 3)
- BLUE (MPV)

10 - empty ---------------------- 10 - 2x RED (CABLE 1 & 4)

So cable colours are:

CABLE 1 - RED, YEL, BLUE, GRN/YEL
CABLE 2 - RED, YEL, BLUE, GRN/YEL
CABLE 3 - RED, YEL, BLUE, GRN/YEL
CABLE 4 - RED, BLACK, GRN/YEL


View media item 83750
I've taken some more pics of the wiring block if you need any more info.

The grey cable from the MPV connects to the yellow cable from the tank stat. From what you said it looks like I don't have the right wiring in place then... ?

Edit: Could anything be done with the black wire that seemingly connects to nothing on the Right side of the block?

 

[D_Hailsham]

I've just looked at the series of pics in your second post, which weren't there when I started my reply. The cause of your problem is obvious when you look at the pic of the timer! There is a switch with the options "water" and "heating & water"; there is no option for just heating. This is a throwback to the days when hot water cylinders were heated by gravity circulation and the radiators by pumped circulation. The programmer should have been changed when the mid-position valve was installed, converting the system to fully pumped.

You will need a new programmer.

The thermostat is very old and probably not very accurate, so it might be worth getting a programmable thermostat. The Honeywell Sundial RF2 Pack 2 is a two channel (heating & hot water) 7 day programmer and a wireless thermostat.

The programmer may be able to go where the exiting time-switch is, depending on the wires available. The junction box will have to be rewired, but that's not a difficult job.

Think about the programmer/thermostat replacement while I look at your wiring.

 

[D_Hailsham]

Right hand connections go to 3x grey sheathed multi core cables behind wall.

It would help if you said which of the three cables each wire belongs to.

 

[djruk]

Right hand connections go to 3x grey sheathed multi core cables behind wall.

It would help if you said which of the three cables each wire belongs to.

Sorry, in my original post I thought I'd implied the switch wasn't capable of CH only - sorry for the confusion.

I've had a look through the wiring and think I've determined what cable each wire is for. I've updated the original wiring post above with the cable numbers. Hope this will help?

In the meantime I'll think about the programmer. The Honeywell looks and sounds good, but someone said they weren't too reliable and advised me to look at the Drayton LP722, but then told the Drayton MPV would need updating first...? I think the Honeywell looks better and the wireless room stat makes sense... I'll carry on looking at the specs and reviewsfor now Would appreciate your thoughts on why the MA-1 might need replacing with newer 2 channel controls? I thought it is OK as it stands?

 

[D_Hailsham]

Thanks for adding in the cable info.

I've managed to work out most of the existing wiring. I have identified what cables 1-3 do.

Cable 1 goes to the boiler
Cable 2 goes to the room stat
Cable 3 goes to the time switch

Cable 4 is a mystery. Can you find the other end and say what it is connected to?

The time switch is a bit difficult to unravel as is more than one cable. Any chance of saying which wire/terminal belongs to which cable?

I have noticed that the pump is incorrectly wired. This could be why the black wire in T3 is for. But don't change it yet.