Damn Halstead Ace..

[ACOperson]

Halstead ace igniting on DHW mode getting to full gas, then not modulating down from the gas rate it is at (water 9.5mb, ch 5mb). Cutting out once it gets too hot.

Both Ntc's ok at room temp & at approx 60 degrees.

All major components ok (pump, fan, etc gas valve resistance seems ok)

Thought the single Honeywell PCB was a dead cert, new one in but no dice. Same problem.

Any ideas? Going to talk to Halstead on Monday...

 

[Rob]

Id personally change thermistors even though readings seem ok.

Could also be blocked HE. Never seem to modulate before cutting out.

 

[Paul Barker]

I had same thing once, went and bought two new ntc's combined cost nearly 50 quid, customer rang, "it's Ok it's working fine now", lost thermisters over the anals of time.

Job's a darned charity half the time. Yet sone idiot who is earning 30k thinks acs is worth wasting his money on.

 

[corgiman]

reckon rob is right

what temp diff are you gettin across the primaries on the DHW HE?

And your right paul great aint we

 

[Agile]

Paul ( ACO ) prefers to charge at the big bits rather than little things like temperature surveys and measuring NTCs.

Consequentially the next thing for him to try is the gas valve!!!

This is one of the more difficult ones with no mod coil and a regulator for the max pressure and then applies a pulse width signal to one of the valve's solenoids.

I am not madly experienced with them but I thought there was a tiny screw for the minimum ( bypass ) gas pressure?

Tony

 

[ChrisR]

Yes there is a small screw, they don't seem to drift particularly.
Sensors are the usual 10k cold. It 's useful to have a variable resistor for things like this. (Or just a few fixed ones). DHWHE is easy to get out.

 

[ACOperson]

Sorry Mr Agile, I did remove & test both NTC's at room temp & in 60 degree water. Both seemed OK giving same resistances.

Voltage being applied to gas valve doesn't alter unless control knobs on front are turned.

The small screw on the gas valve doesn't have any effect on this model According to the instructions which came with the PCB it only has effect on the HE model. I set up the PCB as instructed by this pamphlet (ch max / min, ignition pressure). Still no luck.

The only way I got it to work over the weekend was by decreasing the max gas pressure to 6.3mb using the large screw on the gas valve.

Couldn't measure diff temp as my temp probe is faulty. Going to do so when I go back.

 

[Agile]

The reason this boiler was not modulating is because the plate heat exchanger was a little blocked and the system flow was reaching the cut out temp before the DHW reached the modulation back temperature.

Incidentally there is a revised gas valve/PCB set up instruction sheet perhaps because the one in the MI may not work?

If anybody is going to change a valve or PCB then I will email a copy to any ARGI member through the web site.

Tony