Ravenheat Silver/White star - Hot radiators in summer mode?

[AMK]

I have a ravenheat silver star (I know you all think they're crap, but it was all I could afford at the time and it's worked well for three years)

My problem is I noticed the radiators were hot all day and I assumed it was the timer - a friend with the same radiator has had to replace one. But I think not. Even in summer mode with no CH selected, the boiler fires for about 30 seconds, the shuts off for about 2 minutes, then fires up again for 30 seconds and so it goes on during this time the CH flow and return pipes are pretty hot. The only way to stop it is to switch the boiler off completely.

Also, I'm not sure if it's related but the DHW runs at the right temp for about 5 minutes, goes cold intermittently, then back up to normal temp again.

If it's a timer or PCB or anything electrical, I can replace it myself (I'm a sparky), also if it's anything on the wet side I can flush, and drain as needed. Gas - I've got a tame CORGI friend, but he doesn't do Ravenheats.

Any thoughts before I reach for the yellow pages ?

PS. There was a post on here a while back about ravenheats not sparking, firing but then shutting down. Check the live and neutral are not reversed on the mains supply. They're polarity sensitive

 

[Agile]

I have a ravenheat silver star (I know you all think they're rubbish, but it was all I could afford at the time and it's worked well for three years)

The cynical would say that you have got your money's worth out of a cheap boiler!

Check the sensors to see if they are correct when the boiler is cold. About 25 K

If so check the DHW demand switch as it seems that its stuck in the demand position.

Tony

 

[AMK]

Thanks,

I'll have a look at the DHW demand.

BTW What were you doing up at that hour, I thought I was the only saddo here

 

[gas4you]

Tony's our resident night watchman

 

[Slugbabydotcom]

On your timer 1 and 2 are power supply for timer the other wires should be on 3 and 5 for switching. Timers go often but usually stick in OFF position rather than the ON.
Check your summer /winter switch is working correctly too.

DHW switch works like a brake light switch on a car. With the pin out the switch connection is made and broken with the pin pushed in.
The first ever 'star' boiler I fitted had a stuck diverter valve which didn't operate the pin properly.

I like Ravenheats but these are more like their submarine than their flagship because I end up chasing faults all over the place with them.

With regards your HW cutting off problem

With any later Ravenheat I say that changing the CH thermistor gives you a level playing field to sort out other problems. Testing them isn't always conclusive as the fault could be temperature sensitive or just plain intermittent. Ravenheat state that resistance should be between 500ohm and 20k.

On some models this thermistor gives frost protection ie it will turn your boiler on when there is no other call for heat, so all the more reason for changing it.

 

[Agile]

Are you quite sure you have got that the right way round?

I thought that the diverter rested in CH with the groove allowing the pin to be out and pushing the pin in brought on the DHW? But I could be wrong!

On the ARGI visit to Ravenheat they said all their sensors are 25K cold. But that could have been limited to their current models in production.

Tony

 

[Slugbabydotcom]

With the pin out the switch connection is made and broken with the pin pushed in.

Of that I'm sure.
I believe it is the case that the pin is pushed in while at rest in CH position and a call for DHW allows the pin to come out and make the contact.

Some of the new premix combi's have a red clip on thermistor for DHW and I dont know what those resistances are but I would assume that this is the 25k to which you refer.

Re the green thermistors
I have the 20k / 500ohm reference in my course notes from when I did the course 2 weeks after you did and also from when I went 2 years ago. There is an error on the data sheet I have from them which states :-

20k ohms cold to 5k ohms @ 82ºC.

I tested one at armpit temp a while back and got 7k @ 37º and 9k @ room temp.

 

[Agile]

John Wilson said that ALL their boilers used sensors with a 25K cold resistance. He was holding a green one at the time!

He might have meant all their current models though!

Tony