i All,

We have a heatslave 15/19 which was fine until a couple of days ago. A guy came round from the waterboard to fit us a water meter [uck]. After shutting off the supply, and disconnecting a few joints on the cold feed, he then realised he had the incorrect meter and put it all back again to return sometime in the future. Since then, every 10 minutes or so, the boiler keeps kicking in for DHW.

The central heating is currently switched off [pressure is about 1.5bar if that makes a difference] on the front panel, and the water system is set to on perminatly. Before his visit, the boiler would come on every 2 hours or so, and also when you switched on a tap. Now, it comes on every 10 minutes or so.

Every 10 or so minutes you can hear gurgling in the pipes, and clicking noises come from the boiler as if someone has turned on a hot tap - assume this a relay triggered by a flow switch or something.

Anyway, the boiler then fires up for 30 seconds or so - during this time we get some more clicking and gurgling. It then goes off, and repeats the cycle after about another 10 mins.

The gurgeling sounds like air I guess - but I dont know where. Would air trapped in the closed rad circut cause this to happen, even with the central heating off? I have switched on all the taps in the house - there was some initial splutrering [he didn't leave the taps on when switching the main supply back on] - but thats all gone now.

I could bleed the rads, but don't have a key at the moment - don't want to waste time if it's not that.

If anyone has any ideas, that would be great.

Many thanks

Simon, July 2007

If the burner does'nt fire up then it may be just a pump over-run thermostat that has become over-active and is bringing the pump on briefly to cool the main heat exchanger. This usually only happens after a call for heat or hot water, and switches off after a minute or so.
The gurgling sound could mean air in the rads even though you're not using the system, because when it's in rest mode the outlet to the rads is open ,so if the pump comes on it will still go out to the heating side.
The only other thing i can think of is if the pilot (does it have one)has become too large it would cause the heat exchanger to over-heat etc.

Terry, July 2007

Hi Terry,

Cheers for that - well, the taps on the correct way.

Pre his visit - the boiler used to kick in every few hours or so, assume this was preheat. The boiler isn't that advanced and seems to have only on or off for hot water - I have switched it off and you can still obsever [every 10 mins or so] the relay flicking and the pipes making noises. The burner doesn't kick in though obviously.

The incomming tap is turned half way on. Assume this is to prevent siezing or such? I'm not sure how "on" it was before his vist.

Simon, July 2007

Just a couple of thoughts. Check the incoming stop tap to see if it is opened properly. Some flow switches can operate if the incoming pressure drops. Also check, if he removed the incoming tap, that he put it back the rightway up.(arrow pointing into the house)
If your boiler has a pre-heat function can you switch it off so it only responds when a tap is turned on? This would tell you if it was a fault in one way or the other. The other thing to test would be to unplug the flow switch for a while and see if it stopped. Many of the combi flow switches do have a plug on the wire so they can be removed for repair etc.

Terry, July 2007

Thanks for the reply tony.

He only worked on one pipe - the main cold feed. I have checked, no leaks here.

Before his visit - the boiler used to come on every 2 hours or so, as you say, I guess to keep stored water at temp.

Now it's ever 10 minutes or so, and is driving me mad.

There are only 4 hot "taps" in the house - one in the kitchen, two taps in bathroom, plus feed for shower. None of them are leaking [at least out of the taps!].

I have checked in the loft, none of the pipework is leaking up there.

It's the noise thats confusing me - its like clockwork, funny noise from pipes followed by boiler kicking in.

Simon, July 2007

the boiler comes on to keep stored hot water at temp,it cound be a coincidence that problem occured after water board visit but first thing to check would be
has he left a leak on the pipework he worked on or pipework near by
are any taps dripping,is there a clock room or loft shower room you do not use alot with tap not turned off fully
other posibility water turned off with boiler on and hot water thermostate made slightly out of calibration turn down slightly and see result
just a few thoughts hope helps

tony..tsp heating, July 2007