undergas appliance

[hammers4spanner]

Is an under gassed appliance just noted on cp12 or go down as an ncs ?
1.5 kw under that is not talking 8 kw .

 

[Mike Jackson]

What appliance is it?

 

[hammers4spanner]

was a potterton suprima

 

[mountainman]

Why is it undergassed?

 

[hammers4spanner]

i normally do installs where we get a commission engineer come around after ,now been passed onto servicing and come acroos this today

potterton suprima heat only boiler
working pressurw at meter 23 mbar
working pressure at boiler 22mbar
when i gas rated it got 9.5 kw twice and tag says 11 kw

 

[AWheating]

5 to 10% under on gas rate is normally nothing to worry about if all other checks performed and are correct. Engineers judgement needed. If the pipework is slightly undersized to the appliance but all checks are ok then NCS the pipework.

 

[diamondgas]

H4S your WP seems high. I think you may have measured the p1 inlet supply WP rather than p2 burner working pressure... Chance is that it was less than mi's require at a guess .. ?

 

[hammers4spanner]

p1 inlet supply??
can you enlighten me a tad please

 

[diamondgas]

Certainly my friend ... The suprima 30 works on a BP setting of 9.3mbar, gas rate 1.05m[SUP]3[/SUP]/h, 37.1ft[SUP]3[/SUP]/h --- (taken from mi's) You need to check the gas valve outlet pressure to the burner. It's the test point above the inlet pressure test point

 

[hammers4spanner]

on a service tho shouldnt i take a working pressure from meter between 19 - 23 mbar and then one at appliance on the inlet ?

 

[darren bastin]

The inlet pressure will help identify undersized /blocked pipework. A suprima requires its burner pressure to be measured to see if it is within its range rating. Basically the burner pressure affects the gas rate.

 

[diamondgas]

on a service tho shouldnt i take a working pressure from meter between 19 - 23 mbar and then one at appliance on the inlet ?

As mentioned h4s .. The inlet pressure lets you know of potential issues but the main pressure that'll influence the gas rate will me the burner working pressure. There isn't necessarily a need to investigate the inlet pressure as long as you have sufficient bp maintained! (that'll set the cat amongst the pigeons)

It's only been with the onset of premix burners and zero governors that there's been more emphasis on the inlet WP of appliances and the need for correctly sized pipework ... B4 it wasn't necessarily a major concern TBH

 

[mfgs]

You need to be checking burner pressure, not inlet pressure on these. The earlier suprimas were range rated aswell I think, so the burner pressure may well match the gas rate but you wont know unless you have done a burner pressure.

 

[hammers4spanner]

So doing a service in the absence of MI'S is basically a pain in the back end as you wont get enough data of the tag ,

so am i doing my safety device check correct by checking any passing gas on valve with manometer?

got me thinking now that no one worked with in past services correctly

 

[tamz]

The burner pressure will be on the plate. If it is range rated chances are the arrow sticker won't be on it but you can measure it and check what it should be..

 

[kirkgas]

5 to 10% under on gas rate is normally nothing to worry about if all other checks performed and are correct. Engineers judgement needed. If the pipework is slightly undersized to the appliance but all checks are ok then NCS the pipework.

there a recent TB which states 5% over and 10% under is what we should be targeting as max levels

 

[Mike Jackson]

So doing a service in the absence of MI'S is basically a pain in the back end as you wont get enough data of the tag ,

so am i doing my safety device check correct by checking any passing gas on valve with manometer?

got me thinking now that no one worked with in past services correctly

If they weren't checking burner pressures then they weren't. If you're analysing a range rated boiler you should check with the burner pressure set to maximum and then set the pressure back to as found.

 

[Bernie2]

You know, I often wonder if it would not pay companies to put more easily accessible test points on their products and perhaps a cheap LED on each component that would light up when the component failed. Save a lot of fault finding.

 

[bennygas]

what if the led breaks bernie?:sad_smile: totally agree on the test point idea tho

 

[glenno1]

if led lights were put in for component failure it would possibly encourage more diy repairs

 

[bennygas]

how would you ever engineer a component to self test>? don't really think it's feasible. have an led to show something's energised or similar, but not to try to show if its faulty, surely.

 

[AWheating]

there a recent TB which states 5% over and 10% under is what we should be targeting as max levels

every training center i have been to has always taught 5 over 10 under as a rule of thumb, good to know somebodys finally written it down.

 

[Bernie2]

Yes I think you can get self test components. They just test the known input and output values and light a Led if they do not work. I have an ASUS motherboard that tests the RAM to make sure its compatible and lights a LED if it isn't. Many thermistors work on temperature activated resistance change and then operate heat controls.

Many fitters use a multi meter to test and prove circuities and all that usually does is pass a current through and then measure it to give a reading. You could use a LED with a set component fail level that lights if it is reached.

 

[bennygas]

i'm not having a pop bernie, really i'm not. testing electronics is one thing, but imho a very great proportion of faults that i've come across over the years have their origin not on the electrical side of things (sure, they might have implications for the electrical side of things), but more on the hydraulic or mechanical side of things - and to have some kind of mechanism to test for correct mechanical operation - just unfeasible imho. if it's leds confirming operation of stuff , we've kind of alreagy got things like that -status led codes, some parts have leds to show they're energised etc, and i dare say that some boilers do check that the resistance of some thermistors etc are in range before throwing up a fault code - i guess you could say why put an led on it, if you can just display a fault code? i like the idea though bernie, would be lovely.

 

[Bernie2]

The problem is, I suppose that as boiler makers are searching for the last few % efficiency, they are making more and more of the boiler's controls complicated and so require electronic management systems for them to work properly.

In the car industry it has virtually driven out all the small companies because of the high cost of test equipment and code readers. With a boiler you may get a position similar to that and require a different set of test instruments for each make of boiler and other adaptations for the various models they make.
A small company could probably never afford the outlay.

The boiler makers of course would probably be made up, manufacturers call out charges can be very high. Also they would only need test equipment for their own boilers a small company would need them for as many boilers as there are on the market. So manufacturers would probably like it. The likes of Tescos may be able to compete with them with the Billions they make, but will the small guy trying to scrape a living from servicing be able to do so?

Anyway it would appear we are going more and more toward electric boilers and the like and that probably means there will be even more electronics.

Making things simple for the average small company would give a lot more people a chance of making a living.

There is lots of cheap electronic test stuff on the market already that can test even hydraulic components. If a boiler can emit a code to signify a problem then the same current instead of generating a reading could light a LED. A simple thermocouple shuts a gas valve using the absence of an electrical charge.

A duff fans air pressure switch, signals exhaust gases are not getting out and shuts the boiler down. The same signal could light a LED or some other simple way to signal the failed component. At the moment fitters probably require all kinds of fault finding back up such as i-phone apps, lap tops and MI's, probably beside specialist code books or possibly code readers. If it goes on like that we could need a mainframe computer to repair a simple boiler.