Flow- Vent- Feed -Pump

[desktop987456]

Does the RH knob vary the output or the temperature, do you know?

Yes it does but with that flame rate takes a fair amount of time to reach the temp.

As Rob said may its range rated at min, how do I get the flame level up. When I asked Tech support how do I get into configuration menu, they said its a mod-con on off boiler with no configuration or settings menu!

 

[Madrab]

As Rob said may its range rated at min, how do I get the flame level up. When I asked Tech support how do I get into configuration menu, they said its a mod-con on off boiler with no configuration or settings menu!

Yup, given there's no settings menu or configuration, then everything must be auto loaded and factory set, hence no installer menus to access. If there is no access to any configuration settings then it cannot be range rated directly and will just modulate down to 7.9Kw when needed.

I'd be asking Viesmann tech what could stop the boiler from ramping up to full power under normal operation, given it will when in service mode, which will be for analysing in min/max modes. Only other thing I could think of would be flow/temp through the boiler and it's sensing that full power isn't required (modulating to min power) but without knowing how the boiler sets that, it would be difficult to say for sure.

 

[fixitflav]

Yup, given there's no settings menu or configuration, then everything must be auto loaded and factory set, hence no installer menus to access. If there is no access to any configuration settings then it cannot be range rated directly and will just modulate down to 7.9Kw when needed.

I'd be asking Viesmann tech what could stop the boiler from ramping up to full power under normal operation, given it will when in service mode, which will be for analysing in min/max modes. Only other thing I could think of would be flow/temp through the boiler and it's sensing that full power isn't required (modulating to min power) but without knowing how the boiler sets that, it would be difficult to say for sure.

I was coming to similar conclusion.

The RH knob for temperature setting, (suggested by the thermometer symbol!) and the output range built-in.

Possibly there's an adjustment of gas flow output vs temperature. On the circuit diagram, page 49, the Boiler water temperature sensor 3 and the Return temperature sensor 17 both look they might be adjustable. Maybe Viessmann can comment.

I'm still curious about the LH knob. Selection of NG or LPG will only be done once so it seems odd to have it on the face of the boiler.

 

[fixitflav]

they said its a mod-con on off boiler

Not sure I understand that!

You mention LPG backup in #38. Are you on NG at present? The boiler will expect European NG, nearly all methane, but I once worked on a job in mainland USA where it was different. Might be worth confirming.

 

[Madrab]

Boiler water temperature sensor 3 and the Return temperature sensor 17

Picking up on the same theme, and coming back to when it was asked if the boiler was properly vented and coming back to flow rates through the boiler, the only other mention within the MI that may impact the burner setting is the resistance differentials between the flow and return sensor. It shouldn't have made that much of a difference but that may also be a causality of altering the pump settings.

Page 40 - ■ In the case of differentials >25 K/< 30 K, the burner is operated at lower heating output.

Try setting the pump back to its original setting as a test.

 

[fixitflav]

Page 40 - ■ In the case of differentials >25 K/< 30 K, the burner is operated at lower heating output.

Ah, I hadn't spotted that, must read the manuals more carefully.
So it seems there is scope for at least checking, maybe adjustment, or perhaps replacement. Needs a multimeter!

 

[desktop987456]

I'm still curious about the LH knob

Me too, you need to adjust the fuel setting once in a while. BTW, I am on NG with a btu value of 1050 and WC of 14" and is within the spec sheet of the boiler. I have also read the LH knob can also be used for altitude (>or< 1500m) setting depending on the region.

(mod-con = modulating condensing boiler, with no configuration or settings menu.

to when it was asked if the boiler was properly vented

Yes, it was vented

Try setting the pump back to its original setting as a test

BTW, Pump is also now connected and controlled from boiler board (port 20) instead of wiring center. I will try higher pum setting, last time I checked it started from cold and was on minimum flame whereas it should atleast for a few minutes after starting off should be at full flame.

Thanks as always for your help and support, I will report back.

 

[fixitflav]

btu value of 1050 and WC of 14" and is within the spec sheet of the boiler.

BTU fine. 14" WC ~ 35 mbar, > 25 in the MI, but if it works OK........

(mod-con = modulating condensing boiler, with no configuration or settings menu.

It was the on off bit that confused me, incompatible with modulating.

it started from cold and was on minimum flame whereas it should atleast for a few minutes after starting off should be at full flame.

Yes, that's the outstanding problem. Keep us informed!

 

[Madrab]

whereas it should at least for a few minutes after starting off should be at full flame.

Not necessarily, a lot of boilers start on min and hold there for a few mins as things stabilise and then start to ramp up. Some WB boilers when just switched on go into a purge mode and sit at min for up to 15mins. Obviously not sure about that Vaillant boiler as it may normally ramp up straight away.

 

[fixitflav]

Vaillant

Viessmann!

 

[Madrab]

Viessmann!

Oops ... getting word blind now we're into 11 pages ....

 

[desktop987456]

Oops ... getting word blind now we're into 11 pages ....

and counting....

 

[desktop987456]

Message from Tech support; Ruling out a plate heat exchanger since it is heat only. Is Gas valve serviceable item? Its not, I have been told by Tech Support.
I know for combi's min gas pipe should be 22mm, what gas pipe size should be adequate for heat only boiler.

Gas inlet port on boiler is R1/2 (see attached), after putting the adaptor on male thread of the gas port the size is reduced further down to the gas service pipe, could it be in adequate gas pipe size?
If it is inadequate gas pipe size why does it run fine on Serv mode?

 

[fixitflav]

after putting the adaptor on male thread of the gas port the size is reduced further down to the gas service pipe

Not sure what you mean by that, but Viessmann are clutching at straws IMO. For 13kW, 15mm pipe is fine unless the length is unusual. And that's with supply from a meter at ~ 20mb. You have 35mb. And as you say, If it is inadequate gas pipe size why does it run fine on Serv mode?

Still worth doing the checks on pages 39 and 40. Problem is you don't know the temperature, apart from letting it cool to ambient, when resistance should be 15-20kohm. But that would be a good starting point, to see if it's miles out. To get more readings, the sensor could be removed and put in a saucepan of heated water (with thermometer) but I don't suppose you want to go to that trouble at the moment.

 

[desktop987456]

Viessmann are clutching at straws

Couldn't agree more.

The pipe length is not unusual, its hardly 15 ft from gas service line which is 1.25" from meter.

I also asked viessmann about min pipe diameter for gas line, their response: 'MI asks fr 17mbp at the valve before fire'.

I also stand corrected on WC for gas which is 20mbar where I live and not 35.