Central Heatng not working after Summer

[kieranpage]

Hi guys,

This is my first post on here and i appologise in advance for repeating someone's elses problem thats already been answered but i have looked on the search.

In feburary i was decorating my ground-floor and decided to change my thermostate from the old 1970's dial style to a modern digital style. I installed a SUNVIC TLX7501 and just did a wire for wire swap. After this the heating did not work but I thought very little of it as it was spring and I wasnt using it for summer and thought I would rewire it when I needed it. well guess what. its november now and its freezing!!!!

Two weeks ago I turned the HONEYWELL DIGITAL TIMER ST6300A on for both hotwater and heating (i have used my imersion heater over the summer) and my hotwater works fine, the boiler kicks in when required and its perfect. But my heating does not work. So i studied the circuit diagram and wired it as it showed to the best of my knowlegde (i had 1 blue wire, 1 red(with240 on it) and 1 yellow) i wired it so that the red and yellow short when the thermostate is activeated.

This still made no differnce and the heating still wouldnt work. now strangly enough my upstairs radiators work but i presume this is some bleed off from the hotwater, please correct me if i am wrong. I have opened the valves on all the radiators before someones asks.

Tonight i have completly bi-passed the termostate and hardwired the red (240v) and the yellow (switch) together and then studied the circuit printed on the back of my DIGITAL TIMER (HONEYWELL AS ABOVE). i then connected the wires so that the Central heating will be on. i beleive now that i have ruled out both the thermostate and the timer by doing this. please tell me if i am wrong.

From my very basic experiance (im an eurofighter electricain by trade) i am not putting the fault down to either the pump or the valves. The pump (big red thing near my access hatch) is very hot even though the pipes leading to it are only warm(there is a white arrow dial on it, what does this do??). is this normal or is the pump broken???

Please can someone advise my next move in diagnosis or am i reduced to having to call a plumber!!.

Thanks very much and i wish i could buy the person who helps me a crate of beer!!!

 

[Softus]

For reasons of laziness I haven't looked up the TLX7501, but in my experience digital roomstats require only two wires - these form the circuit that needs to be made for the CH demand to be generated.

Unfortunately the colours of your wires don't define their function - you need to trace the connections of these wires at the programmer or wiring centre.

If you can post back the connections then we can tell you which two should be used at the roomstat end - the third one should be made electrically safe (at both ends).

BTW, the reason for there being three wires originally is that analogue roomstats require three wires (another topic really).

 

[meldrew's_mate]

From my very basic experiance (im an eurofighter electricain by trade) i am not putting the fault down to either the pump or the valves. The pump (big red thing near my access hatch) is very hot even though the pipes leading to it are only warm

Kieranpage, it does indeed seem that your pump is somewhat kaput. Check for voltage at the input. If it's a Grundfos pump or similar you can usually remove a large screw at the centre of the shaft axis. Proding a terminal driver down this hole will reveal if the pump shaft is actually turning. I say this because the pump body is normally just a tad cooler than the water running through it.

Hope this helps; do you really have a big hand in keeping our first line of defence in the air?

 

[Softus]

How is the water to DHW and CH controlled? Do you have any motorised zone valved in your system?

 

[kieranpage]

How is the water to DHW and CH controlled? Do you have any motorised zone valved in your system?

Hi mate, thanks for getting back to me. What do u mean by DHW??

I have no idea if i have valves in my system. how would i find out?

many thanks

kieran

 

[kieranpage]

For reasons of laziness I haven't looked up the TLX7501, but in my experience digital roomstats require only two wires - these form the circuit that needs to be made for the CH demand to be generated.

Unfortunately the colours of your wires don't define their function - you need to trace the connections of these wires at the programmer or wiring centre.

If you can post back the connections then we can tell you which two should be used at the roomstat end - the third one should be made electrically safe (at both ends).

BTW, the reason for there being three wires originally is that analogue roomstats require three wires (another topic really).

Hi,

The red wire has 240v live on it. I belvie the blue is a neutral and the yellow is the swithced wire. i copied the wiring off of a mates simlar system. At the moment i have hard wired the 240 red to the yellow switch wire.

is this any help?

thanks

kieran

 

[kieranpage]

From my very basic experiance (im an eurofighter electricain by trade) i am not putting the fault down to either the pump or the valves. The pump (big red thing near my access hatch) is very hot even though the pipes leading to it are only warm

Kieranpage, it does indeed seem that your pump is somewhat kaput. Check for voltage at the input. If it's a Grundfos pump or similar you can usually remove a large screw at the centre of the shaft axis. Proding a terminal driver down this hole will reveal if the pump shaft is actually turning. I say this because the pump body is normally just a tad cooler than the water running through it.

Hope this helps; do you really have a big hand in keeping our first line of defence in the air?

sorry for my misquoet, i meant i AM putting it down to the pump or the valves. Also, i foudn out tongiht that the boiler doesnt fire up hen the heating system is activated on the digital timer. I will have a look so see if the pump has voltage and also if it is turning.

and yes i do work for aerospace on the eurofighter. cool aircraft!!!

 

[Softus]

kierenpage

No offence intended, but you're making it difficult to help you.

There are three-port valves, of which you would have one, that control the primary water flow to both DHW (domestic hot water) and CH (central heating), and two-port valves, of which you would usually have two, that control the primary water flow to either DHW or CH.

If you have one or more MZVs, then, invariably, it is these that provide the electrical feed to the boiler and pump, by means of a microswitch in the valve motor casing - the electrical feed to the valve is provided by the programmer via a thermostat (room and/or cylinder).

In addition, some boilers will operate the pump as a way of (a) dispersing heated water after the burners have shut off, and/or (b) stopping the pump from seizing during long off periods (e.g. summer).

This is much dumbed down description of common systems - there are many variants, but the first step with yours is to identify what controls you have.

If you have MZVs, and suddenly neither the boiler nor pump is operating, then the fault is likely to be either the programmer or the MZV. If you have two two-port MZVs, and the boiler fires in one mode but one the other, then you've narrowed it down already. If you've made any wiring changes recently, then an additional possibility is a poor or wrong connection.

Could you list all of the components in your system, and have a recap of the behaviour?

FYI, motorised zone valves (not valved as I previously misspelt) are increasingly common components - they look like this.