Halstead free standing boiler ignition working but no hot water or heat?

Combi-boiler-turn hot water tap on/off and the heating stops for ...

singletrackworld.com/.../combi-boiler-turn-hot-water-tap-onoff-and-the-...

Combi-boiler-turn hot water tap on/off and the heating stops for 20secs ... hot watertakes priority over central heating so when you run the hot tap, heating is ... Yeah onmy worcester combi there is a diverter valve - it feeds either the heating or ...

My central heating works but I have no hot water - 24'7 ...

https://www.247homerescue.co.uk/my-central-heating-works-but-i-have-...

Diverter valves switch heat between the hot water and the central heating. When youturn your hot tap on, the diverter valve temporarily shuts off the water supply ...

Does your boiler keep switching itself off? Here's why ...

www.dhs-uk.com/does-your-boiler-keep-switching-itself-off-heres-why/

Jul 7, 2015 - ... Bathroom Suites, - Showers, - Wet Rooms, - Taps and Accessories, Information and ... Low water pressure can cause your boiler to turn itself off. ... boiler is not turning off, you aren't getting the amount of hot water you require. ... If there is air in your central heating system, then your boiler may shut down.

If this is in a RV the propane monitoring valve may require more gas flow to turn on than the water heater requires. A central heating system requires substantial gas flow so when the monitoring valve opens to fire the central heating, there is enough gas flow to also fire the water heater.

Hot water is gravity fed through your pipes. When you turn the faucet on the water will flow through the pipes. If your hot water heater is natural gas driven relight the pilot. Same if oil fueled. If electrical, check fuse to see if it has blown or the circuit breaker has tripped. If either has tripped, replace it and if it blows again the heater has a serious failure, you might need to buy a new one. If pilot won't light on gas unit, try relighting after 5 minutes, could be a bad thermocouple.

Difficult to get too specific without knowing if you have gas or oil. Also, I am going under the assumption you mean the burner shuts down, not the whole heating system. That being said, all heating appliances have whats called a safety curcuit. Each control has the ability to shut down if certain critera are not met. There is a sensor that senses light down the blast tube. If no light is sensed in a predetermined time period, then the sensor cuts power to the burner. This stops delivery of fuel so if it does ignite you wont blow up.
(I suspect that the ignitor and burner shut down simultainously.)
It may be the sensor (cad cell eye) is doing its job, however why is the question. Could be a number of things including the fuel delivery, ignition, improper air adjustment, etc.
No qualified professional should diagnose a problem unless they are in front of the appliance. I recommend you find a licensed qualified heating techician. Hope this helps.

The boiler and the hot water heater are (2) seprate units.

sounds basic, but make sure the electrode is in the pilot flame
check the overheat thermostat is not jammed on
disconnect and join wires together for temporary override check and run boiler.

overheat stat

Check to see if diverter valve is in domestic mode or heating mode.

I know of no limitations on the temperature of the inlet water for any boiler. The warmer the water, the less energy it will take to heat it to desired temp and the colder the water, the more energy it will take. Extreme temps over an extended amout of time in either direction can stress a unit and could possibly, only possibly reduce service time.

the boiler should modulate to controll the radiator temperature but the central heating will go off whilst you are drawing hot water