Temporarily need hot water with thermostat (can't remember)!

[jackecole]

Small problem that I need clarification on as I can't remember 100% the correct order of events...!

To get to the point, my cylinder thermostat is not switching ON when required ... The programmer lights up for HW on but nothing. Heating is OK.

So using my multimeter, set to AC Volts, I tested and the cyilnder thermostat COMMON terminal had 236 volts, but the cylinder thermostat CALL terminal had 0.

Just to make sure the cylinder thermostat wasn't calling and in fact the cylinder thermostat switch was definitely stuck in the OPEN position, and to make sure my programmer switches HW ON /OFF switches were not faulty and sending the wrong signal(s) - I removed the HW OFF wire from the programmer, from the terminal block (the terminal block also had 2 other wires - GREY wire from 3 port valve and the Satisfied terminal from the cylinder thermostat. After removing this wire, the terminal block, which now had just 2 wires in it still had the same, 236 volts reading.

So, I now need a new cylinder thermostat. But I cannot get one until tomorrow morning. I am at work now but found this website thanks to google!!

What I can not remember is ... the correct way of getting hot water with a faulty cylinder thermostat (temporarily tonight until I get a new cylinder thermostat tomorrow). Is this way correct; if it is not or I have missed something out, i'd be absolutely appreciative if anyone can remember the way to do this trick properly...

Leave the HOT WATER OFF wire from the programmer out of the terminal block (and temp. make safe)

Then turn on just the heating at the programmer with room stat high (door open possibly to keep room temperature down).

This should then stall the 3 port valve to mid position and give heated water to both the hot water and heating circuits whist the room stat is calling, thus heating my hot water cylinder?

Is this correct, or do I need to remove another or a different wire from the terminal box?

 

[jackecole]

nonbody abe to remember ?!

 

[seco services]

you can bridge the stat out for tonight.
in your wiring centre take a wire from the hw on into the orange.
leave your hw on at programmer. then you'll have constant water and the heating can come and go as it likes.
it won't take long to heat the cylinder for the night then you can turn hw off at the programmer cause you won't have a stat to regulate the temp.

ps take the two original stat wires out and remember where they go.
as the stat will be sending live up the grey

 

[jackecole]

i suppose this is one way... i don't have any spare wire though. i'd rather do it the way i know (sort of remember) though .... just need clarification.

 

[D_Hailsham]

What I can not remember is ... the correct way of getting hot water with a faulty cylinder thermostat

When the valve is in HW only or mid-position (HW and CH), the boiler is turned on/off via the cylinder stat. So, even if you stall the valve in mid-position, the boiler will not light if the cylinder stat is faulty.

The grey wire controls whether the valve is in mid position (0 volts on grey) or in CH only position (230v on grey). The voltage is supplied either from the HW OFF of the timer or the SAT terminal of the HW stat, depending on what causes the HW to go off.

So what you are proposing will not work.

 

[JohnD]

it would also be an idea to turn the boiler stat down to 60C or so, to prevent the cylinder reaching scalding temperatures.

 

[jackecole]

I did hear this would work ...

BTW when the valve is in mid position, the boiler and pump and turned on/off by the orange wire (which is operated by the motor from the 3 port moving across after power is applied to the white wire) if Honeywell

is bridging the gap the only way i can get my h/w then?

 

[jackecole]

it would also be an idea to turn the boiler stat down to 60C or so, to prevent the cylinder reaching scalding temperatures.

no chance of that as i can't get any hot water to the cylinder!!

 

[seco services]

you will do if you change the wiring

 

[Boxerman]

a long shot and perhaps too obvious but do you have an immersion heater?

 

[jackecole]

hah-yeah i wish... we had it blanked off years ago as the original one was old and we didn't think we'd ever need one ... how wrong was we

ok so do i just need a short piece of wire as suggested by seco services? what size thickness?

 

[JohnD]

who can answer me this...

you say you have a faulty cyl stat and are going to replace it with a new one.

A stat is a switch. It connects COM to Term 1 or Term 2 depending on temperature.

If you installed a 6A 2-way light switch,you could manually switch COM to Term 1 or Term 2

If you installed a choc-block or a JB you could switch it (using a screwdriver)

So why do you need to do more?

p.s.the boiler is usually supplied via an FCU (sometimes a plug) with a 3A or 5A cartridge fuse. So 0.75mm wire (as used in table-lamp flex) will be adequate but you can use bigger if you have it handy. Check your fuse rating.

 

[seco services]

nick abit off the old womens hoover

 

[jackecole]

ha cant do that!! just wanted 2 check i only needed a singe core wire!

 

[D_Hailsham]

BTW when the valve is in mid position, the boiler and pump and turned on/off by the orange wire (which is operated by the motor from the 3 port moving across after power is applied to the white wire) if Honeywell

Wrong! The orange wire does not come into operation until the valve is in the CH only position. It just appears to be be providing 240v because it is connected to the same terminal as the HW stat CALL terminal.

Read Mid-position valve working and Diagnostics