Grant Combi Boiler to Hive (No Hot Water)

27 Jul 2021
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United Kingdom

I had a new Grant Vortex Combi 26 boiler installed 1 year ago. I also bought a Hive thermostat and wired it in myself. Having never owned a combi boiler before I thought all was well. Central heating came on when I wanted and I had hot water.

Then I realised that although I could get hot water, it was only when the heating was on. Simply turning on the hot water tap does not fire up the boiler.

This is what I've done/tried so far...

I wired the hive (terminals 1 and 3) into the 2 room stat terminals (and removed that loop).
I have removed the timed CH and timed DHW loops.
The hot water switch is in the 'timer' position.

When I turn on the hot water tap all the lights come on as you would expect - Flow, Demand and DHW Pump but the boiler does not fire up. With those lights all lighting up I assume that the water pressure is good and the flow switch is working ok. Like I said this is pretty much a brand new boiler.

If I change the hot water switch to 'constant' it fires up straight away so that works - but obviously I don't want my boiler running 24/7.

If I replace the wiring loop back on to the DHW is will fire up when the hot water switch is in the 'timer' position - but again I don't want the boiler running 24/7.

Any ideas?
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Hi Ian.

The last time I tried that it just fired up straight away without any hot water taps on.
I'll try it again tonight.

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Put the loop back in and left it to run for about 15 minutes until it went off - just as you said Ian.
Thanks again!
Was on holiday for last few days so I'm only getting to test this properly now...

So when I turn the boiler on (with no heating or hot water demand active) is runs for about 15 minutes to build up a hot water store and then turns off until I turn a hot water tap on, runs for a bit and then turns off again - Perfect. However, every so often it fires up the boiler even if I don't use a hot water tap (I assume to maintain a hot water store) but I'd rather that didn't happen.

A friend of mine told me his combi boiler used to do that but he has an 'eco switch' to stop it coming on all the time - My boiler doesn't have that.

Any ideas how I can get round this?

Are you sure your mates boiler is not a Gas combi, common to have an eco button on Gas combis, but not on oil combis
Yeah his is gas.
So is this how an oil combi boiler is supposed to work? Just keep firing up to heat water on the off chance you may need it.
Yes it will fire every now and again to keep the store warm, gas and oil combis do not work the same way

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