boiling coming on when it shouldn't - or should it?

[arc]

Hi guys, wondering if you can help me out here. Moved house, and in the new house is a heating system that is pretty alien to me. I'm used to combi boilers, and this is not one.

The boiler is a Baxi Inset 2. It is behind the fire in the back lounge. The timer/programmer is Danfoss FP15, it is upstairs in the bathroom along with the hot water cylinder, a pump and a Siemens MA-V322C 3 way valve. The programmer is branded with Servowarm.

It is currently set for the HW to come on at 7am for an hour to heat the water for the morning. It then comes on again 5pm i think for another hour. That is it. The heating is set to OFF.

Every 15 minutes or so, the boiler kicks in and runs for around 30 seconds and then goes off again. The boiler does this all day, regardless of what the timer is set to. It has been doing this since i moved in (Septemeber) - so it's not a recent thing with the recent spell of cold weather. Even with the HW and CH both set to OFF, and the thermostat set to min - the boiler still comes on and off when it feels like it.

Is this normal, or is this a frost protection system gone nuts?

Also, the upstairs radiators warm up when the hot water cylinder is hot. The pump doesn't come on, but i'm guessing this has something to do with the 3 way valve? I've never really looked at a system like this, so i don't know what it should and shouldn't do. I dont want all the upstairs rads coming on and cooling my hot water cylinder down!!

what's going on with this system.. has it gone loopy, or is it doing what it should?

Many thanks
Mark

 

[chrishutt]

Sounds like the wiring is incorrect. Check out the wiring for a 3 port mid position motorised valve (generally known as Y plan) at, say, the Honeywell site. The boiler and pump should only come on when the motorised valve moves to the appropriate position in response to calls for heat from the programmer, cylinder stat and room stat.

 

[arc]

with the programmer set to OFF for HW and CH, the room stat set to min - then surely it shouldn't come on at all.

I will check the wiring, thanks.

 

[arc]

ok, i've had a look at the wiring:




So looking at this..

It's wired as Y plan system, L4 and L5 are cut but L6 is not meaning the boiler does not require pump overrun.

There is nothing connected to the HTG valve block, so the frost stat is not installed.

looking at the plumbing side of things, it does look at bit OTT.. i tried to draw what was going on, but gave up and just pointed the video camera round a bit

http://tackycheese.net/images/misc/ch_mpg.avi (6.6mb)