central heating only comes on with h water, stumped engineer

[bonkersbill]

Hi all, i have put some rad flush in to try to remove this as a problem.
As the boiler kept going for 8 minutes when i turned the valve position 180 degrees manually with CH on, i thought i would try HW only, this turned the boiler off after about 30 seconds which suggests that the CH port is blocked, i am going to change the valve when i drain the system of the radflush.
But i also ran the system with CH and HW in mid position at 180 degrees but this did not heat the rads, the boiler would keep going for minutes on end then shutting down as if satified then starting up minutes later.
I appear to have found 1 problem but not the cure but i will only be sure when ive changed the 3 port valve.

 

[bonkersbill]

Hello again, i have flushed the system, changed the 3 port valve and i have got no change, the boiler still shuts down after 30 secondswith CH on only and does not come back on unless i put the HW on. So far i have done
System flush
new actuator
new 3 port valve
new room thermostat
new programmer
i've had 3 engineers out who have all said that the wiring is working ok and all have given different possible reasons as to what the problem is from faulty boiler to blocked or wrong sized pipes or faulty actuator/valve (replaced both, no change), all require major work which they will not gaurantee will solve the problem. There have been lots of suggestions which i have gone through with out any change, i have just reveiwed them again and one came up that mentioned the thermostat earth should be connected to L3 and not the earth, i have red to 1, blue to 2, yellow to 3 and the earth to the earth in my new honeywell thermostat, should the earth be connected in with the yellow wire to number 3? Other than that does any body have any more ideas as tearing my house apart looking for possible faults does not appeal to me.

 

[doitall]

Connect the earth to any of the phase terminals and you'll get a BANG!!!!.

Whats the make and models of the programmer, room and cylinder stat, and the actuator number compete, is the anything after the HSA 3.

What's the boiler make/model as well.

 

[bonkersbill]

Honeywell room stat & programer st9400c
danfoss hsa3 with hsv valve
danfoss cyl stat type at

 

[bonkersbill]

Boiler is a baxi back of fire boiler

 

[doitall]

Model of the room stat and boiler.

 

[bonkersbill]

baxi bermuda inset 2
honeywell has t40 and t636ob1028 inside the front cover

 

[doitall]

Can you post some clear pics showing the wires, if not PM me an email address.

 

[bonkersbill]

i will see what i can do, cheers

 

[Tom1981]

This is confusing the hell out if me, going to have to read this several times. Quoting different brands of thermostats and actuators means nothing! The wiring is the same underneath, unless it's a motor open motor close system or 4 wire.

I'll read this and give my professional input, not a DIYers

 

[Tom1981]

Funny question, has the pump been changed recently? Or have the pump valves been touched?

 

[doitall]

Almost certainly a wiring fault, if Bill preferably posts the pics to me we can get it up and running in no time.

he could set the programmer in the heat only mode, then connect the white/brown (MV) to a permanent live the valve should go to htg and the boiler/pump should work

 

[matt1e]

Almost certainly a wiring fault, if Bill preferably posts the pics to me we can get it up and running in no time

I disagree, reading through I'd say it was definatly a circulation problem on the Rad circuit, the op needs to sort out his pipework

Matt

 

[DP]

Matt, do not let the name doitall confuse you. You are in the company of godlike creature when it come to plumbing. Go down on one knee and say 'please sir, do you think it could be? etc'

 

[doitall]

Almost certainly a wiring fault, if Bill preferably posts the pics to me we can get it up and running in no time

I disagree, reading through I'd say it was definatly a circulation problem on the Rad circuit, the op needs to sort out his pipework

Matt

Matt,

If it was a circulation problem, why does it work when the DHW is on.