Boiler undersized question?

[Agile]

You n check the power input at the gas meter yourself. Look at the FAQ on this site.

It would also be good if you could learn to talk in kW as they are the units the UK has used since 1980.

The gas rate measures the input power and that will be higher than the output because your boiler is not very inefficient.

When did you last have it serviced?

Tony

 

[vessy_73]

It would also be good if you could learn to talk in kW as they are the units the UK has used since 1980

Tony

Lol, ok habit I guess!

Boiler last services a year ago, I have the manual so I will check the gas flow rate using the meter, good shout.

 

[vessy_73]

Ok, so did the gas meter test this evening, took 59 secs to fully rotate, this gives a boiler draw of 18.5 kW, the manual for the boilers says low is 18.68 input for 14.95 kW output (51000 btu) high is 21.98 input for 17.58 kW output (60000 btu). So the boiler is adjusted for minimum output!!

Would it be ok for me to adjust the gas pressure using this method? Just for testing of course to see that everything is ok, I will then get someone qualified to check and adjust if necessary. I have the manual and the procedure is pretty basic, max input of 21.98 kW means about 50 secs for a full rotation of the meter, will probably aim conservative at 51!

 

[muggles]

No, it needs to be adjusted properly with proper gas equipment and assessed to ensure that it is still burning safely post-adjustment. Get an RGI in to do it

 

[vessy_73]

Ok, gas pressure has been adjusted, it was on the low setting and has now been set to max, system now gets to 60 degrees in around 30 mins and house temp rises much quicker.

Only issue now is kettling! Boiler sounds like a kettle warming up or like the cold water header tank filling constantly, you can hear it in the next room! also what sounds like small air bubbles moving round the system once it gets to around 70 degrees, gas guy says either lime scale or corrosion in the heat exchanger, he also said that there is slime on top of the f&e water and recommended the system needs a good cleaner.

This surprised me as the system was drained and flushed through using mains water 3 months ago when I replaced the pump, Sentinel inhibitor and descaler were both added on refil.

All rads have been re-balanced and set around 10-11 degree drop, boiler has 14 degree drop during heat up, I increased the pump to 3 and the boiler difference dropped to 10-11 degrees but the rads were running around 8 degree drop.

Welcome any comments regarding cleaning, de-scaling and temp drops.

Nothing is ever simple!! Thanks

 

[oph]

The size of the distribution system also needs to be considered. If 30K btu's worth of rads are downstairs yet the bulk of it is fed in 15mm then that wont help the situation

 

[vessy_73]

The size of the distribution system also needs to be considered. If 30K btu's worth of rads are downstairs yet the bulk of it is fed in 15mm then that wont help the situation

Not sure I fully understand, flow to me is obviously enough as rads have a temp differential of up to 8 deg, 22 feeding downstairs with 15mm feeds to each rad, total of 5 rads, only one of these has its lockshield fully open. Should I just leave it at 14 deg split at the boiler to keep the 10-11 on the rads?

 

[oph]

Assuming you zone valnes are the airng cupboard on the first floor then your floe and return dropper to the downstairs circuit will be in 22. Thats fine but at what point do they start reducing down to 15mm. Could be that theres 15mm pipe being asked to do too much. I have that problem in my very own house but I cant be arsed to do anything about it to be honest. Plus a minor detail of I dont get paid for it either........

 

[vessy_73]

Assuming you zone valnes are the airng cupboard on the first floor then your floe and return dropper to the downstairs circuit will be in 22. Thats fine but at what point do they start reducing down to 15mm. Could be that theres 15mm pipe being asked to do too much. I have that problem in my very own house but I cant be arsed to do anything about it to be honest. Plus a minor detail of I dont get paid for it either........

Get your point, God knows is the answer, concrete floors, definitely 22mm from valves, down to ground floor, I think it's ok as I can get the 8 degree on the index rad (or 11 deg at pump speed 2) and it's a big rad (6500 btu)

I'm going to leave the pump in 2 for a while as I'm getting optimum drops across all rads, means the boiler cycles a bit earlier as it hits 75 deg and return is only 61 but hey ho, until I fit a new modulating boiler I'll live with it, the furthest rad is a fair distance from the boiler so a few degrees drop on F & R I guess is inevitable.

 

[muggles]

Glad you've got it mostly sorted, does sound like the boiler & system could do with a good clean though, or put some boiler noise silencer in the system. It would be possible to just powerflush the boiler if there's access to the pipes above it...

 

[Agile]

Just because the power input is correct now, it does not mean that the power output is also correct.

In fact if it is kettling then the output is likely to be significantly below the rated power.

You need to close one valve on each rad and introduce a can of Sentinel X200 into the system and use it to heat the hot water only for a few cycles until hopefully the kettling will subside. It can be left in the system.

Then and only then you can expect the heat output may be close to the maker's specs.

Best to take some steady state temperature measurement before and adding the X200.

Good luck.

Tony