Worcester 30si

[Hobo128]

Allo, I installed a Worcester 30 si today and was doing the commisioning. I put it into service mode(press and hold service button for more than 10 secs) boiler goes into over drive for 15mins. Checked the working pressure at the meter 19mbar then checked the inlet working pressure at the boiler inlet 18mbar. This is all good? The thing that is confusing me is that in the MI it has a drawing, (Figure 70 on page 33) its a diagram of a meter then the boiler then the gas valve. The meter is 19-23 the boiler is 18-22 and the gas valve is 16.5-20.5. I understand that worcester say they will allow a 2.5mbar pressure drop from the meter to the gas valve but when im testing the burner pressure on the gas valve im getting -4mbar. what is that about????

Also when im gas rating the boiler it should be 3.24m3/h but im getting 2.94m3/h

 

[mfgs]

There is no burner pressure on these, its a zero governor. The three points of reading are the meter, the pipe just before it enters the boiler and the inlet of the gas valve being the last one.

 

[Hobo128]

Ok sounds good, but what about the gas rating??

 

[mfgs]

Its within tolerance so its fine as long as the FGA results are ok.

 

[Nostrum]

Gas rate could just be the gas valve needs tweaking. Out of the box they are rarely bang on and as this has a direct influence on the gas rate it could be why your seeing slightly less.

if you've got a 1mb drop from meter to gas valve inlet then your pipe size is spot on as you normally get more from my experience. Most of these appliances will still gas rate fine with 12-14mb at inlet (not that it makes it o.k to have this)

 

[Hobo128]

Its within tolerance so its fine as long as the FGA results are ok.

Am I right in thinking that it's + - 5 % gas rate tolerance?

 

[vern]

Yes as the return temp makes a huge difference to gas consumption, read Tech spec it alters by 2 KW

 

[Hobo128]

Ok so I see what we are saying here but if you calculate -5% of 3.24 it isn't within the tolerances!

3.24 x 0.05 = 0.162 3.24-0.162= 3.078m3/h this is the absolute minimum allowance we can have. Im getting 2.94m3/h when gas rating?????

 

[Nostrum]

Its +5 or -10% in kW if I remember.

what was co2 on max ? If it's below manufacturers (9.8 is it? They've changed them all a few times) then it will gas rate lower.

in service mode the return temp shouldn't make any odds as the boiler is stopped from modulating, the fan speed is fixed for the test.

 

[Hobo128]

I'll be honest, I havn't checked the ratios yet, Im on and off the job.
Ill give you that one, I just read that the maximum it can exceed the MI is 5% so that is +5% but I can't find where it says how much it can be under. I remember reading it somwhere but don't no where, I feel like im getting somwhere now. Any ideas???

 

[Nostrum]

Can't think off the top of my head where it's written, I've not got anything here, maybe viper book or similar?

I wouldn't get too cut up about it until you've checked co2. If you've got 19mb inlet and the gas valve is set at factory for 20 then you'll have a lower gas input but fan will still be spinning at preset speed so co2 will be down due to leaner gas air ratio. Follow the guidance in MI on how to adjust. (2mm and 4mm Allen key required)

Adjust max to mi and I put money on it all being good.

 

[AlexGas]

Tb 071

 

[Hobo128]

Tb 141 its in. It states it can exceed MI 5% or be under by 10% unless stated in manufactures instructions.
Ok so I checked the ratios today, it came in at 10.2 Co2 and 8.2 co2 min. I adjusted them both and got the to 9.8max and 8.8min which is correct. I didnt have time to gas rate it but by adjusting the ratios will this give me a different gas rate????

 

[zeebeedee]

Tb 141 its in. It states it can exceed MI 5% or be under by 10% unless stated in manufactures instructions.
Ok so I checked the ratios today, it came in at 10.2 Co2 and 8.2 co2 min. I adjusted them both and got the to 9.8max and 8.8min which is correct. I didnt have time to gas rate it but by adjusting the ratios will this give me a different gas rate????

No. Your only adjusting the gas/air ratio.

 

[bewsh]

Adjusting the co2 won't make a difference to the gas rate. But I wouldnt be too concerned about the gas rate you're getting.

 

[AWheating]

did you gas rate on a smart meter/ on of those stupid ones you have to keep pressing the buttons on? i find them a right pain in the bummywummy.

 

[Billy Bob Bob]

if i had 19mb at the meter the ESP would be coming out

 

[diamondgas]

Tb 141 its in. It states it can exceed MI 5% or be under by 10% unless stated in manufactures instructions.
Ok so I checked the ratios today, it came in at 10.2 Co2 and 8.2 co2 min. I adjusted them both and got the to 9.8max and 8.8min which is correct. I didnt have time to gas rate it but by adjusting the ratios will this give me a different gas rate????

In my opinion you will have a difference. When adjusting the low and high gas valve rate you're messing with the amount of gas being allowed to flow at the constant fan speeds set by the electronics. The important thing to get right is the ratio as this will effect efficiency and nox products .. IMHO 🙂

 

[Hobo128]

Adjusting the co2 won't make a difference to the gas rate. But I wouldnt be too concerned about the gas rate you're getting.

Why not, it's out isn't it?

 

[Hobo128]

if i had 19mb at the meter the ESP would be coming out

Will they still come out if it's right. I thought 19mb was the absolute min it could be. Dont forget, the boiler is on service mode and the gas cooker is on too.

 

[Billy Bob Bob]

Will they still come out if it's right. I thought 19mb was the absolute min it could be. Dont forget, the boiler is on service mode and the gas cooker is on too.

personally would want to see 21-22 mb leaving there ,yes they would attend

 

[dancinplumba]

Tell em its only 18 🙂

 

[Nostrum]

They don't even check, they walk up the path with the new governor and flexi tucked under their arm

 

[tamz]

Why not, it's out isn't it?

No it is within 10%