central heating prob

[D_Hailsham]

How can you have a midposition valve on a gravity HW system?

The OP means that HW cylinder is fed from the cold water tank in the loft. I know it's not what the pros would call a gravity system, but you have read what most OPs say very carefully as they do not know the terminology .

Surely if the valve was stuck in CH position, the boiler would be running 24/7 (auxillary switch on MV operated)

You are assuming it is a zone valve.

 

[D_Hailsham]

i dont hear a thing , with it turned on or off, and i cant move the lever at all, its stuck fast

I think there is some confusion. The thing labelled "HW HW/CH CH" is not a lever, it is just an indicator. It is not meant to be moved.

The lever I am asking you to move at one end of the valve, above either the HW or CH pipe, in a slot. Moving this will not affect the position of the "HW HW/CH CH" indicator.

You said earlier

the bottom switch moves freely

If that is the lever which slides in the slot and it does it when the power is off, it means that the valve is stuck open. You need to change it

i take it the valve u mentioned would be a direct replacement, just unscrew the old and fit new valve. has it the same wiring, as the wiring that goes to the junction box is not labelled.

Yes it's a direct replacement.

The wiring is the same. Each wire is a different colour but both valves use the same colours. So you just swap white for white etc. Cut the cable about 6 inches from the junction box (turn the power off first!) before changing the valve. Then you know which terminal the wires connect to.

You will have to drain the system down to below the level of the valve.

 

[DP]

DH, unless I misunderstand you I would take following quote to refere to a motorised valve

so i think its the acl mid position valve, the lever on the side is stuck at the bottom and cant move.

If mid position valve is in home position, HW will work but no CH
Midposition, both CH and HW work
CH position. Only HW works but now auxillary switch operates to fire boiler with timer not calling for CH

 

[G1zm0]

the heating system is as follows

the water storage tank that supplies cold water to cylinder (gravity)and toilet ect,

then theres the boiler and the valve ect,

i was told by the gas board it was a gravity fed one, maby he waswrong

it does have a pump and a small expansion tank at boiler, so must be a fully pumped system then

 

[echoes]

If the valve was stuck in the CH-only position, the boiler would only fire when the programmer & room stat call for CH. In this position, White is connected to Orange to fire the boiler. But without 240V on White, there will not be 240V on Orange unless HW is also calling. And the boiler will NOT fire 24/7.

So valve stuck in Ch-only is consistent with the symptoms.

 

[DP]

Echoes, I stand corrected

 

[G1zm0]

the lever is at the bottom( or to the right if turned up right) , when i put the hot water on only the radiators heat up but no hot water, and same with radiators and both selected from programer.

so only fault i can think of is the valve,

 

[G1zm0]

the lever is at the bottom( or to the right if turned up right) , when i put the hot water on only the radiators heat up but no hot water, and same with radiators and both selected from programer.

so only fault i can think of is the valve,

might just get the y plan kit and change over the valve assembly and the controls, i have a frost stat as well on the wall

 

[G1zm0]

the lever is at the bottom( or to the right if turned up right) , when i put the hot water on only the radiators heat up but no hot water, and same with radiators and both selected from programer.

so only fault i can think of is the valve,

might just get the y plan kit and change over the valve assembly and the controls, i have a frost stat as well on the wall


is there a way to check the controls panel is working ok, when the radiators are warm the room thermostst is at 10 (lowest setting) and radiators remain warm

 

[D_Hailsham]

might just get the y plan kit and change over the valve assembly and the controls,

Why buy a kit with an old fashioned mechanical thermostat when all you need is the valve?

is there a way to check the controls panel is working ok, when the radiators are warm the room thermostst is at 10 (lowest setting) and radiators remain warm

You could try following the diagnostic procedure in How a mid-position valve works

 

[G1zm0]

i was going to get it as the programer is a 7 day one and not 24 like the one i got, then i could set it for various times as i work weird shifts

 

[D_Hailsham]

i was going to get it as the programmer is a 7 day one and not 24 like the one i got, then i could set it for various times as i work weird shifts

I would suggest you buy just the components you need. For example

Honeywell V4073A valve

Honeywell CM907 (wired) or CM927 (wireless) programmable 7 day thermostat (heating only).

You existing programmer could be retained for controlling the hot water times. (A 24 hour one should be sufficient as times rarely change.) It can be relocated in the airing cupboard near the HW tank etc.

 

[G1zm0]

gonna go and order that part tmoz, and drain system half down and flick the c.u off to disconnect wires (after noting them)

the programer i , i want to be able to controll different days at diff times like

mon, tue from 5am to 8am, heating and water, * every 2nd week
wed thur not set as im not in house* every 2nd week
fri same as mon* every 2nd week
sat ,sun , to come on at 5pm till 10pm (both)
and vice versa the next week

the units that were mentioned was for heating on
i saw this one 1x ST9400C 7 DAY PROGRAMMER


the thermostat i have is a british gas one, can this be changed out for a digital one


i will fit the valve 1st and get the thing working,

to drain the system do i just block up the header tank in loft
open the drain cock outside to drain system and open radiator bleed valve,

the expansion tank with the pressure gadge , will that drain when i open the valve?

and might put inhibitor into the system, how do i add this, via header tank?

 

[D_Hailsham]

gonna go and order that part tmoz, and drain system half down and flick the c.u off to disconnect wires (after noting them)

There should be a switch/plug/fused spur near the boiler of the junction box which controls the complete heating system.

If you cut through the cable of the old valve about 6" from the junction box before removing the valve, you can the swap the wires over one colour at a time.

to drain the system do i just block up the header tank in loft
open the drain cock outside to drain system and open radiator bleed valve,

the expansion tank with the pressure gauge , will that drain when i open the valve?

You can't have a header tank and a pressure gauge! How many tanks do you have in the loft - one or two? How big are they?

I don't know of any programmer which covers a two week cycle; they are either 24 hour or seven day.

Yes, you can change the BG thermostat for a digital one.

 

[G1zm0]

the only switch i see near the boiler is a fesd one, but when i switch it of it switches the controls panel of

and the wires run to the junction box then 2 wires go down under ground.

the tank im on about is a small red one at boiler, a red one abt size of a football with a pressure gadge on it, i sometimes have to top this up as the system makes a noise if its below 1 bar

and at top of boiler theres a bit that spews water sometimes i think this is the pressure release valve.


might take pics and post, how do i test the motor in the mid valve incase its just thats thats away