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My glow worm ultracom 18hxi goes to low flame at 68 degrees…

My glow worm ultracom 18hxi...

My glow worm ultracom 18hxi goes to low flame at 68 degrees boiler is set to 76 dont understand why

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Customer reply replied 7 years ago

When it goes to low flame, the boiler doesnt go to high flame again till temp drops to about 45, then it cycles again

Customer reply replied 7 years ago

Just doesnt seem to modulate properly either high or low flamelarge temperature differential before the flame comes back up

Answered in 1 hour by:

10/23/2015

Plumber: Andrew Smith, Engineer replied 7 years ago

Andrew Smith, Engineer

Category: UK Plumbing

Satisfied Customers: 4,029

Experience: Domestic Gas, Commercial Gas, LPG, Unvented Hot Water, Part P Electrical, Commercial Catering

Verified

The boiler should modulate depending on the returning water temperature.

Is the boiler not keeping up with the required temperature - is the house chilly?

The boiler does this to use gas efficiently.

Customer reply replied 7 years ago

It is not modulating andrew, goes from low to high. The differential before going back on full flame from low is about 20 degrees. To takes ages to heat up the system.

Plumber: Andrew Smith, Engineer replied 7 years ago

Are you able to check the voltage to see if the gas valve modulates when being told to, or is defective?

Customer reply replied 7 years ago

What should the voltage be, i am a retired electrical contractor i can check it.

Plumber: Andrew Smith, Engineer replied 7 years ago

Thats great. Try this;

http://www.glow-worm.co.uk/glow-worm/ultracom-hxi-instn-157270.pdf

Page 35 onwards - just check the settings are correct for what you need - max temp, anti-cycling time, etc

Customer reply replied 7 years ago

They are at factory settings in the manual Andrew.What is the second diagnostic menu for, doesnt mention how to get into it and what you can change.

Plumber: Andrew Smith, Engineer replied 7 years ago

These will be factory adjusted settings, do not alter these as this PCB is able to be fitted across their whole range and could make it useless if you cannot get back into them.

Have you tried turning down the anti cycling time to 5 minutes so it can fire more often?

Customer reply replied 7 years ago

No i havent andrew, i will try that, thank you. Ill come back to you tomorrow if thats ok.

Plumber: Andrew Smith, Engineer replied 7 years ago

No problem

Customer reply replied 7 years ago

Hi Andrew,
I seem to have got to the bottom of my problem.
The boiler is modulating but when the cylider is up to temperature and turns the boiler off, the next time the cylinder calls for heat, high flame comes in and the boiler goes to high temp before the gas valve has time to modulate the flame down. This makes it look like it isnt modulating, have you any idea what i need to do to stop this.

Plumber: Andrew Smith, Engineer replied 7 years ago

Can you check the power to the modulation coil and see if it drops but the flames stay high.

I need to know if ther gas valve is doing what it is told.

Customer reply replied 7 years ago

Modulation valve steady 15 volt. Water temp 69. When i reset the boiler it fires up steady 15 volt on modulator, then before the modulator gets chance to do anything else the boiler gets to high temp and cut out. Boiler set at 80.Take about 4 seconds to get to high temp on full flame.

Plumber: Andrew Smith, Engineer replied 7 years ago

Ok, the boiler should be modulating down before then.

The gas valve is doing what it is told.

Have you cleaned or replaced the primary thermistor?

Customer reply replied 7 years ago

Cleaned and still same.

Plumber: Andrew Smith, Engineer replied 7 years ago

My first though would be spend the £20 and replace it.

It is that and the PCB that dictates the modulation.

Andrew Smith, Engineer

Category: UK Plumbing

Satisfied Customers: 4,029

Experience: Domestic Gas, Commercial Gas, LPG, Unvented Hot Water, Part P Electrical, Commercial Catering

Verified

Andrew Smith and 87 other UK Plumbing Specialists are ready to help you

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Customer reply replied 7 years ago

Ok thanks for your advice Andrew.

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