I recently bought and had installed an Stelflow unvented hot water cylinder, but the guy who installed it cocked-up the electrical connections to the thermostat causing a short circuit.. I don't want to use him again as I don't feel he knows what he's doing when it comes to dealing with electrical wiring I have something of an understanding of electrical wiring diagrams generally and am familiar with am 'S' plan wiring diagram, so feel reasonably confident in tackling this myself, but am confused by pamphlet instructions, (see d) below) which came with the cylinder, and seem at odds with the wiring diagram shown on the cylinder company’s website, which I discovered later. I have provided some photos, with wiring diagram to explain where my confusion lies. I will have to go into some detail so please bear with me, and it would be much appreciated if someone who genuinely understands plumbing electrics could help me out here.
a) The thermostat is of a Duastat control type, with a manual Adjustor, box (A) on the right has the water temperature regulated by the user. Also a Limiter , Box (L) automatically cuts off the boiler if the temperature ever reaches a maximum limit.
b) So instead of one standard 3 terminal box there are 2 boxes, with 2 independent circuits. Box (A) (Adjustor terminal box photo) shows 4 terminals.
c) These are marked on the website wiring diagram as (C), (E), (2), (1) respectively. Only 2 terminals are shown to be actually connected. A(1) is taken as live to H/W programmer ON J(6), which is usual. A(2) is shown as a terminal with no actual wiring connection. I’m assuming that this is the case. Finally, L(C) is taken as the output voltage to junction box J(9). So L(C) should always have the same voltage (on/off).as A(C), which is presumably switched to A(1) internally, until the required temp is reached when it switches to A(2), thus opening the circuit in A.. Before that happens A(C) bridges live to L(2), which in turn is switched to L(C) until the maximum temp is ever reached, when L(C) switches to L(2). Ideally that should never happen as that is a safety device, thus relying on A(2) as the cut-off instead.
d ) It is the instruction pamphlet that really causes the confusion. There are 2 cables shown feeding both A and L each with 2 wires per cable (Fig. 5). As you can see, a Live is shown connected to L(C). which is misleading, as it is A(1) which should be taking live voltage from J(6), according to the wiring diagram in c) above. Furthermore, A(1) is seen connected to a neutral, whereas that terminal is supposed to be fed from the programmer HW ON via J6. Nor is there supposed to be any neutral feed to the thermo boxes, so what are they talking about? And what does terminal ‘U’ in the pamphlet mean?
Many thanks.
a) The thermostat is of a Duastat control type, with a manual Adjustor, box (A) on the right has the water temperature regulated by the user. Also a Limiter , Box (L) automatically cuts off the boiler if the temperature ever reaches a maximum limit.
b) So instead of one standard 3 terminal box there are 2 boxes, with 2 independent circuits. Box (A) (Adjustor terminal box photo) shows 4 terminals.
c) These are marked on the website wiring diagram as (C), (E), (2), (1) respectively. Only 2 terminals are shown to be actually connected. A(1) is taken as live to H/W programmer ON J(6), which is usual. A(2) is shown as a terminal with no actual wiring connection. I’m assuming that this is the case. Finally, L(C) is taken as the output voltage to junction box J(9). So L(C) should always have the same voltage (on/off).as A(C), which is presumably switched to A(1) internally, until the required temp is reached when it switches to A(2), thus opening the circuit in A.. Before that happens A(C) bridges live to L(2), which in turn is switched to L(C) until the maximum temp is ever reached, when L(C) switches to L(2). Ideally that should never happen as that is a safety device, thus relying on A(2) as the cut-off instead.
d ) It is the instruction pamphlet that really causes the confusion. There are 2 cables shown feeding both A and L each with 2 wires per cable (Fig. 5). As you can see, a Live is shown connected to L(C). which is misleading, as it is A(1) which should be taking live voltage from J(6), according to the wiring diagram in c) above. Furthermore, A(1) is seen connected to a neutral, whereas that terminal is supposed to be fed from the programmer HW ON via J6. Nor is there supposed to be any neutral feed to the thermo boxes, so what are they talking about? And what does terminal ‘U’ in the pamphlet mean?
Many thanks.
