# Gas Inlet Working Pressure in Vaillant 630 system boiler

#### hughs

The gas inlet working pressure in the Vaillant EcoTec plus 630 System Boiler is 16.5 mbar. The recommended pressure for this boiler is in the range 17 – 25 mbar.

The gas flow rate is 3.2 cubic metres per hr for natural gas. The recommended rate in cubic metres per hr is:
Nominal – 3.24
+5% - 3.40
-10% - 2.91

I am told that the output pressure from the gas meter is set at its maximum.

If the working pressure is very slightly less than the recommended rate, what are the implications? If I need to increase the gas pressure, what do I need to do?

Is the gas flow rate ok, noting the above readings?

Anything else that I should consider?

If you are getting 16.5 at the gas valve inlet, you will have approx 19.5 mBar at the gas pipe inlet under the boiler.

Ecotec's 'lose' about 3 mBar between gas cock and gas valve.

If you are getting 16.5 at the gas valve inlet, you will have approx 19.5 mBar at the gas pipe inlet under the boiler.

Ecotec's 'lose' about 3 mBar between gas cock and gas valve.

Thank you Dave.

The recommended readings I noted were noted in the installation booklet and related to the pressure at the boiler. Therefore I presume I would need that level of pressure at the Boiler. Is my presumption correct? Even if it is slightly less, should I worry?

If you are getting 16.5 at the gas valve inlet, you will have approx 19.5 mBar at the gas pipe inlet under the boiler.

Ecotec's 'lose' about 3 mBar between gas cock and gas valve.

Any thoughts on the flow rate of gas? Is this ok for this boiler, noting the readings I noted?

I think, from what you have posted, you are missing the most vital point. Ecotec's must be set up with an FGA to give 9.0% CO2 case off (NG)

Your mathematical 19.5 mBar is good enough as long as you only have 20.5mBar at the meter.

If you mean 'gas meter set for max' that you have 23 mBar WP at meter, then you have a 3.5mBar drop across the carcass, so the installation pipe work is undersized.

Have you installed this, or just servicing it?

I think, from what you have posted, you are missing the most vital point. Ecotec's must be set up with an FGA to give 9.0% CO2 case off (NG)

Your mathematical 19.5 mBar is good enough as long as you only have 20.5mBar at the meter.

If you mean 'gas meter set for max' that you have 23 mBar WP at meter, then you have a 3.5mBar drop across the carcass, so the installation pipe work is undersized.

Have you installed this, or just servicing it?

Thanks again Dave.

An engineer has just installed it. Unfortunately I am not that knowledgeable on the subject, so please bear with me. Noting what I wrote and your comments, does it mean that I should increase the pipe size (I presume for part of the supply from the meter to the boiler)? At the moment, the pipe size is 22mm. Would this solve the problem?

Without being there to see for myself and work out the gas pipe sizing I can only approximate and say yes some of the 22mm should have been replaced with 28mm.

All the 831's that I have ever fitted, quite a lot by now, all state in the MI's that the 'perfect gas rate' of this appliance when on full for DHW should be 3.3m3/hr

I assume your installer did have an FGA to set it up with Did he leave a print out of the readings/performance of the boiler?

Without being there to see for myself and work out the gas pipe sizing I can only approximate and say yes some of the 22mm should have been replaced with 28mm.

All the 831's that I have ever fitted, quite a lot by now, all state in the MI's that the 'perfect gas rate' of this appliance when on full for DHW should be 3.3m3/hr

I assume your installer did have an FGA to set it up with Did he leave a print out of the readings/performance of the boiler?

Thanks again Dave.

The engineer did not leave any readings except for the ones I quoted and the central heating flow (78 F) and return (61 F) temperature.

The pipe length from the meter to the boiler (all 22mm except very small length at the end which is 15mm) is approx 17m. There are eight 90 degree bends (of which 5 are rounded bends).

Do you feel I need part of the pipe replaced with 28mm? If so, would say the first 7 to 8 metres suffice? This would be convenient from the practical setup of the pipes.

Separately, what would the implications be if I do not replace the pipes?

So in effect you have aprox 21m of 22mm copper pipe.

Although text books will say approx 15m is ok for this boiler, I always work to a maximum of 12m.

As pipe comes in 3m lengths usually, I would replace the first 9m with 28mm.

This would also be dependent on whether any other gas appliances come off this same pipe run.

As you can tell there is a bit of thinking and working out to do with proper pipe sizing, not much , but enough to make the appliance struggle to work and comply with regs.

Get your installer to change this pipe for you. It must be done by an RGI and after all if he is an rGI it should have been part of the quote he gave you

Leaving it like it is won't harm the boiler. I do wonder if he used an FGA to set it up though

So in effect you have aprox 21m of 22mm copper pipe.

Although text books will say approx 15m is ok for this boiler, I always work to a maximum of 12m.

As pipe comes in 3m lengths usually, I would replace the first 9m with 28mm.

This would also be dependent on whether any other gas appliances come off this same pipe run.

As you can tell there is a bit of thinking and working out to do with proper pipe sizing, not much , but enough to make the appliance struggle to work and comply with regs.

Get your installer to change this pipe for you. It must be done by an RGI and after all if he is an rGI it should have been part of the quote he gave you

Leaving it like it is won't harm the boiler. I do wonder if he used an FGA to set it up though

Thanks very much Dave for your thoughts.

I definitely get the message that the pipe should be changed (at least the first 8 to 9 metres). If I change it, will it increase the gas inlet pressure at the boiler?

I appreciate you noted that the current set-up will not harm the boiler. However, will it make the boiler inefficient? Any other implications (if I do not change anything)? It is important that I understand this part!

What would the approx cost be for replacing say 9 metres of gas pipe to 28mm (greater London rates)? The access is fairly easy. The gas pipe rises from the wall mounted gas meter to the roof of garage and goes along the length of the garage.

So in effect you have aprox 21m of 22mm copper pipe.

Although text books will say approx 15m is ok for this boiler, I always work to a maximum of 12m.

As pipe comes in 3m lengths usually, I would replace the first 9m with 28mm.

This would also be dependent on whether any other gas appliances come off this same pipe run.

As you can tell there is a bit of thinking and working out to do with proper pipe sizing, not much , but enough to make the appliance struggle to work and comply with regs.

Get your installer to change this pipe for you. It must be done by an RGI and after all if he is an rGI it should have been part of the quote he gave you

Leaving it like it is won't harm the boiler. I do wonder if he used an FGA to set it up though

One part I forgot to answer was whether he used flue gas analysis to set up the system. If this means measuring the flue gas, then I do not think so (although I may be wrong). He measured the gas pressure at the meter and boiler and the flow of gas at both ends. Hope this helps.

So in effect you have aprox 21m of 22mm copper pipe.

Although text books will say approx 15m is ok for this boiler, I always work to a maximum of 12m.

As pipe comes in 3m lengths usually, I would replace the first 9m with 28mm.

This would also be dependent on whether any other gas appliances come off this same pipe run.

As you can tell there is a bit of thinking and working out to do with proper pipe sizing, not much , but enough to make the appliance struggle to work and comply with regs.

Get your installer to change this pipe for you. It must be done by an RGI and after all if he is an rGI it should have been part of the quote he gave you

Leaving it like it is won't harm the boiler. I do wonder if he used an FGA to set it up though

Thanks very much Dave for your thoughts.

I definitely get the message that the pipe should be changed (at least the first 8 to 9 metres). If I change it, will it increase the gas inlet pressure at the boiler?

I appreciate you noted that the current set-up will not harm the boiler. However, will it make the boiler inefficient? Any other implications (if I do not change anything)? It is important that I understand this part!

What would the approx cost be for replacing say 9 metres of gas pipe to 28mm (greater London rates)? The access is fairly easy. The gas pipe rises from the wall mounted gas meter to the roof of garage and goes along the length of the garage.

Any further thoughts on the above? Would really appreciate help in particular with whether changing the initial section (say 9 metres) of pipe to 28mm will increase the gas inlet pressure at the boiler. Also thoughts on the cost of replacing the pipe would be useful.

Post deleted

I was responding to "The gas inlet working pressure in the Vaillant EcoTec plus 630 System Boiler is 16.5 mbar. The recommended pressure for this boiler is in the range 17 – 25 mbar." without reading the rest of the post.

i thought 1/2 a millibar insignificant in this issue. Correct me if i am wrong.

One part I forgot to answer was whether he used flue gas analysis to set up the system. If this means measuring the flue gas, then I do not think so (although I may be wrong). He measured the gas pressure at the meter and boiler and the flow of gas at both ends. Hope this helps.

You can't commission an Ecotec without an FGA.

As said the boiler won't be hurt, but it just points to a sloppy job that doesn't comply with current regulations.

If the boiler has been set up for 9.0% CO2 then it is working correctly.

While you are right that anyone fitting a band A boiler should really check co2, the industry wholesale hasn't owned this philosophy. If I didn't have an analyser I would fit boilers whose manufacturers are confident to set their own boilers up and not specify the installer do it, of wich there are many producing band a boilers which the installer is not required to analyse.

Followed through with the fact that two weks later the figures will have changed as the heat resisting pad at the back of the gianoni undergoes changes.

Buderus have an amaising tolerance, as long as you check the pressure is within tolerance when ensures them of the correct gas air ratio they say c.o. less than 400ppm (which I would consider huge) and boiler is a goodun.

seems the gianoni heat exchanger is the seat of the fine tolerance demanders' problems. Just as it will be the cause of many scrap boilers when sludge fills it's small pathways.

But as long as people will learn to keep their systems clean (which would require a massive demographic change of industry clientelle) the boilers will likely last 20 years.

Anybody with a stainless steak heat exchanger tha hasn't had a powerflush with magnaclean with the install is a complete and utter fool who deserves what they get in 5 to 10 years time.

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