Boiler coming on even though heating/water are off?

[marty50]

Hi all


I've just moved into a new (although not "new build" new!) home and have a question about the heating/water system that I hope someone may be able to answer.


We have a hot water tank in the upstairs airing cupboard, a tank directly above it and also a small tank in the loft (I haven't investigated that yet, but am presuming it's connected). A Grundfos Alpha2 pump is connected to the system here too, and the h/w tank has a dial/temp control connected (wrapped around the jacket). An Ideal Mexico Super 3 RS/70 floor standing boiler is installed in the kitchen (manufacture date 1997) and there are iflo controls to the heating/water system on the wall in the airing cupboard, near the tank. There is a Honeywell thermostat for the heating in the hallway. Other than an unmarked, fist-sized white box in the airing cupboard (electrics for pump?) that's about it I think.


Anyway - the question. When the controls on the iflo are both set to 'off' (and the c/heating thermostat is also set to the lowest/off), I have heard the boiler lighting up on a few occasions. I'm far from an expert, so the only thing I can think of is that this is meant to be happening and it's the water tank being topped up when the water temp dips beneath the level set on the dial? If this is the case, what's the point of the 'on' setting on the iflo controls for hot water?


The Grundfos is set to 'PP1' currently, which is supposedly for TRV systems with no minimum flow requirement. There are some TRVs on some radiators so I'm not sure if this is correct, but we seemed to be getting a fair bit of banging in the pipes (which seemed to be mainly in the wee small hours... great for waking us up!) when it was set to I, II or III (fixed speed operation, for systems without TRVs) so I changed it to see if it made a difference - which it has, although I'm not sure if its now correct.


Hopefully the above makes sense. Just want to know if this seems like a normal thing or whether I should get someone more knowledgeable to come have a look?


Thanks!

 

[bigads28]

Do you have valves on the pipe after the pump? Zone valves with plastic or metal heads?

Sounds to me like a stuck end switch in one of these valves.

 

[Ermintrude]

Or it's gravity hot water

 

[marty50]

Thanks for the replies!

A bit of a shameful shake of the head here... the 'fist-sized white box' I posted about earlier, turns out that's a Sunvic SZ 2301 zone valve. It's all the way to one side at the moment (marked 'Normal Use' as opposed to the other side, 'Flushing Only'). There's also red twist-valve below it on the same pipe which was almost closed, if that helps with anything?

 

[marty50]

Hello again,

Just thought I'd add a bit of extremely basic(?) info, but on Saturday I didn't switch the water on at all. I did hear the boiler come on at a couple of intervals so when it came around to around 6pm and I went to wash up the dishes, I did half expect to have hot water. I did not however - it was warm, but presumably that was just water from the tank.

Sunday I put the water on and as expected, it was sufficiently hot when required later in the day.

Does that offer any pointers to anyone?

Cheers

 

[stevetheplumber]

regardless of whether its gravity or fully pumped hot water there should be nothing running when the clock is offnext time you hear it you need to investigate what is actually coming on does pump run does boiler light
imnot genned up on the new pumps so someone else may tell me they have a timer in them for exercising the pump
the other thing is if the boiler is out side or in an exsposed location is there a frost stat this will over ride the clock

 

[Whyme]

Like stave said if the controls arent calling or a frost stat isnt it shouldnt fire..Sounds like a knackered clock.

 

[jtsplumbing]

Best thing is to call someone in , its difficult to say what the fault is, so better if you get it checked out when some one is on site and can see what is going on else its just guess work, could be any number of things, and you would be even more confused by some of the reply's you will get on here

 

[Bronze_tap]

Hi all
I have heard the boiler lighting up on a few occasions. I'm far from an expert, so the only thing I can think of is that this is meant to be happening and it's the water tank being topped up when the water temp dips beneath the level set on the dial? If this is the case, what's the point of the 'on' setting on the iflo controls for hot water?

Quite a few digital boiler controls have pump "anti-seizure" feature, which runs a system for a few minutes every 24h or 12 h. It runs even when the device is in the off position (but connected to the mains power). Some would only run the pump/fan (if integrated into the boiler), but others would send a short call for the heating (if external to the boiler).

I used to have a mysoon programable thermostat, which would run a boiler for 1 minuter every 24h. And this feature was described in the manual.

 

[kay-jay]

do you no harm whatsoever to change your crappy sunvic valve!

last time i came across this problem it turned out to be a stray live from the zone valve. do you have one zone valve or two?
if its two follow the wires to the wiring centre, undo the cover and with all stats and programmers with no demand, use a voltage tester on the orange wires from each valve. if you get a 230/240 reading on one of them then that is the faulty valve.

 

[GasmanxxxR1]

Ive had this problem a few times, always in conjunction with a baxi solo, but it might be the same with your boiler. It was basically the Grundfos alpha 2 sending just enough volts down the switch live to turn the boiler on. Get an engineer in to check this out.

 

[marty50]

Thanks for all the replies & suggestions folks!

Think it's probably for the best that I ask someone who's got a bit of an idea about these things. I hoped it might be something I could work out through trial and error, but seeing as I've got to have someone in anyway to remove/cap off some gas pipes for some old fires I might as well ask them to have a quick look whilst they're here.

If it gets sorted I'll post up the answer I'm given here just in case it helps anyone else at some point