boiler cutout- causes and remedies?

Hello,

I have just installed (myself) a 3 port valve fully pumped system at home, but when I switch on the CH the boiler only fires for around 15 mins before switching itself off

I have turned up the boiler thermostat but this makes no difference

the hot water circuit is working fine

is the most likely cause airlocks? I have bled all radiators

other possibilities:

I have wired valve/controls according to manufacturers instructions, which has included leaving out room stat as I have TRVs on all rads and making suitable wiring mod in wiring centre to compensate. The old system I replaced was odd (to me) and included a powered thermostsatic valve on the primary heating coil to the cylinder. the old controls could turn this valve on and off and the user set the temp. it had all sorts of balancing gate valves to provide a bypass, but when I modified the system I replaced all pipework to the cylinder for this three port arrangement. it has an air release valve in the relevant place, and all feed and vent pipes are correctly placed too.

Any ideas on what my next course of action should be?

thanks

Ben

Reply to
watereed2003
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Like what? You are supposed to a boiler interlock, to prevent the boiler needlessly cycling.

Reply to
Doctor Drivel

??? I understand the boiler shouldn't run unneccessarily, but its not working at all. maybe i have explained myself badly...

I want to test the CH but after 15 mins the boiler turns off. it has not even begun to heat the rads, so surely an interlock is irrelevant at this stage? wouldn't that only be relevant if the return temp was too high?

Reply to
watereed2003

Hi Ben,

Firstly, can you get any heat to the radiators when you have heating and hot water on at the programmer both at the same time? Does the 3 port motor run when there is a demand for heat to the rads? If not try manually opening the

3 port valve. It should show how to do this in the istructions for the valve.

Secondly, make sure there is no air in any of the high points, if any heating pipes are in the loft look out for either manual or automatic air vents. open these, if there are any, to clear any trapped air.

Its always better to fit a thermostat to the system. It will stop the boiler cycling un necessarily. Especially as they are not that expensive or difficult to fit.

Andy

Reply to
Andrew

If you have wired it as per some incorrect information published by Honeywell then you will probably have omitted the "HW off" wire from the programmer to the grey wire on the 3 port valve.

You also need to install a room stat and loose the trv in that room (just remove the head)

Reply to
Matt

I installed AAV on pipework right next to cylinder on supply to top of coil, and manually opened 3 port when filling to let air out. I assumed this would bleed both DHW and CH circuits

do you think I should install a separate AAV on CH circuit ?

I will wire in stat as several people have suggested this, though the patch I used was recommended by the Danfoss Tech Dept

thanks

Ben

Reply to
watereed2003

My info was from Danfoss Randall tech dept, who made all of the kit I'm using. It was a Danfoss contractors pack. I had already worked out the fix myself and rang to check. it just involved connecting the "call" terminal on room stat terminals to another terminal in the wiring centre

thanks

Reply to
watereed2003

It all depends on the set up of your system. if after the 3 port valve the pipes go up to the loft and then drop down to the radiators, then you will need some sort of air vents on both the flow and return to clear any air locks. This assumes that all the radiator vales including the lock shield are open. Did you manually open the 3 port? at least that way you should have hot water flowing towards the radiators.

Andy

Reply to
Andrew

thanks I will try this

Reply to
watereed2003

thank you all for your help.

Having discussed this with various people I am convinced I have the solution now, and I am going to draindown entire system and install extra AAV on CH circuit and rebleed all rads. I will also install room stat in suitable place to stop cycling in future.

I will close this topic now and hassle you all again when it doesn't work!

cheers

Reply to
watereed2003

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