P/Ton Netaheat / Kingfisher MF

thought flame rectification was a ssytem that allowed the main gas valve to open? - Soggy said that it would fire even though there was no rectification

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Yes. Pilot will light but not rectify to full gas.

Kev explained it perfectly.

I appreciate your an apprentice and you want to learn (I still am and ive been an engineer a long time), but take it one step at a time.

Given then answers, you wont develop the knowlege experts such as kev and agile have.

David

If your not told, and you dont ask, you dont learn

yer right fella

ask and ask how i learned

and tought the bairn (corgiman)

Copious quantities of alcohol, I've heard

I thought it was because the flame rec current was compared to the earthing on the boiler.

Because the Neutral is effectively bonded to earth by the REC (regional electricity company) a reverse polarity connected boiler would not sense the flame rec current.

If you have a half wave DC rectifier, surely the polarity of the AC supply makes no difference, you will still get half wave rectification? It is either AC or not, the polarity of the connection will make no difference, other than you may see the 'other half' of the signal?

bster said:

bster is lost

if reversed polarity - the pcb receives an upside down wave (as it is a 1\2 rectified system) and hence senses a fault?

apoligies if i'm annoying you! - your only one of many today

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you don't annoy me fella pick me brain

afore i go to the states and pickle it

It depends how the flame-current recognition circuit works. Some (Old) boilers only look for a current, which is fine until there's a short or lump of dirt between the probe and jet.

Some apply an AC voltage with respect to earth and check for the current only being positive, they don't have to care about the mains. If there's ever a negative current - lockout. (Eg Ariston). Boilers which use switch-mode (smaller transformer) dc power supplies tend to work this way.

Some look for a match in current while the mains is positive with respect to neutral, which should also be earth. If the mains is reverse-polarity, the mains would be going negative while they're looking for a positive current through the flame, so wouldn't detect it.

If you use a half-wave rectifier, only the positive voltages from the mains (with resp to neutral) get through. There's no voltage at all when the mains goes negative. So no detection, which means "flame failure".

You get "flame failure" if there's either no current during the correct cycle, OR current during the wrong one.

Does that help?

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Moderator's note (not to you Chris)

I took out some bad tempered posts.

Why is P&CH forum so curmudgeonly?

M R
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