boiler gas rate tolerances

[cascas]

When measuring gas rate is a +5% / -10% tolerance from the manufacturers rate applicable for all boilers?

Valiant specify a gas rate, and a +5% / -10% range, Ideal and WB give a single nominal rate, and gloworm give a min and max gas rate where the minimum is that of the boiler at the lowest modulation.

 

[Billy Bob Bob]

When measuring gas rate is a +5% / -10% tolerance from the manufacturers rate applicable for all boilers?

Valiant specify a gas rate, and a +5% / -10% range, Ideal and WB give a single nominal rate, and gloworm give a min and max gas rate where the minimum is that of the boiler at the lowest modulation.

its all down to what the manufacturer specified in the mi,s if in doubt give them a ring for guidance

 

[REDSAW]

i was always told +/-5% either way and my gas inspection bloke sort of agreed.

there is previous threads on the same topic from last sept i think.

 

[cascas]

The MI gas rates tend to be based on a different cv. i.e ideal use 38.7 - which itself gives a error of around 3.5% lower

 

[GrahamM]

If I get 22 or 26KW on a 24KW boiler and FGA is good I am not going to worry about it.

 

[AWheating]

i have always been taught +5%, -10%.

 

[gasmarc]

5% either way , not that it has ever been an issue

 

[cascas]

I have a boiler. MI state gas rate 3.13m3/hr have gas rated at 2.91m3/hr with OP of 18.5Mbar (MI state that 1.8mb is lost at measuring point so therefore 20.3mbar). This is over 5% but under 10% would find this acceptable.

 

[Mike Jackson]

I was always taught +/- 5%. Anything outside this tolerance is NCS or AR depending on the appliance. On most modern modulating boilers I would class it as NCS.

 

[cascas]

Boiler is a ideal logic 30k. inlet OP when measured at boiler test point is 18.25mbar. Ideal have already confirmed that there is a pressure drop measured across the test point of 1.8mbar for the 30kw. Therefore inlet pressure just over 20mbar.

I would be tempted to ncs as I would expect within 5% for rate in MI and I am at about 7.5%. However as I recall, valliant do quote -10% /+5% in there MI. I have contacted ideal, and await there advice. In the meantime, any ideas of the cause? (if any)

 

[AWheating]

how many times did you gas rate it? Personally if i got a bad value i would repeat the gas rate once or twice and take the average value. The tollerances are designed to account for human error as much as anything else.also some times even in chimney sweep mode you may get alittle modulation.

i would except +5% and -10% if fga readings were good.

 

[GrahamM]

Boiler is a ideal logic 30k. inlet OP when measured at boiler test point is 18.25mbar. Ideal have already confirmed that there is a pressure drop measured across the test point of 1.8mbar for the 30kw. Therefore inlet pressure just over 20mbar.

I would be tempted to ncs as I would expect within 5% for rate in MI and I am at about 7.5%. However as I recall, valliant do quote -10% /+5% in there MI. I have contacted ideal, and await there advice. In the meantime, any ideas of the cause? (if any)

You are being too picky in my opinion.

Vaillant are one of the few manufactures who have caught on the unwritten rule about measuring errors and now refer to it in their MI's.

This is not an exact science here. There are many variables that can affect your gas rate figures. Your figures are close enough, and as I mentioned before, as long as the FGA and all other safety checks are sound; this job is a guid yin!

 

[deano1011]

Back when it was corgi i was told on one of my inspections that up to 10% either way was ok.