Replacement radiator is colder at bottom than it is at top.

[DP]

Tony wrote

You need to measure the gas at maximum AND at mimimum as I requested so that we can know that the boiler is able to modulate properly.

Can you tell fluff how he should go about taking the said pressures (him being an enduser) and how you would FORCE the boiler to stay at max burner to make sense of gas useage. Also, how do you force this boiler to stay at min rate without interfering withe the modcoil?

Any hot water measurement is meaningless unless the hot water flow rate is set at the tap to about 11 litres per minute.

What do you think I am trying to get at????

Fluff, power to the boiler is turned off so that you do not waste fuel while letting things stabilise. Purpose of collecting water over 15 seconds is to establish what the flowrate to the hot tap is. It should be 11 l per minute. Purpose of letting the cold water flow and monitor the temperature is to establish when the temperature of cold water has bottomed out. Then switch the power on and take readings off hot tap to record temperature. Purpose of looking at the A light is to see if the burner goes out.

 

[fluff29]

DP - I am a she. Hence, why you have to sometimes make things abit simpler for me.

Don't think any man would have a user name as fluff.

Also, thank you for explaining the tests. It sometimes helps to know what you are trying to do and how to go about it.

 

[Agile]

DP - I am a she. Hence, why you have to sometimes make things abit simpler for me.

Don't think any man would have a user name as fluff.

The late DJ, Alan freeman who did the Top of the Pops on the radio for about 50 years had the nickname Fluff.

I suspect you actually have a man doing bucket tests for you.

Unfortunately in these days of gender equality you should not suggest that females are in any way inferior ( at least not publically ).

 

[DP]

Sorry Fluff, will used correct gender term next time.

 

[fluff29]

Hi all

Have done some tests.

Boiler been put to maximum of 9 on DHW and CH.

- Pump set to III

- 3 litres of water from hot tap (with boiler switched off) in 15 seconds.

- Checked gas over 2 minutes (I have a metric metre). HW set to 9, turned on HW on. Boiler fired for 2 mins. Big flame stayed on all the time. B light stayed lit all the time the boiler was firing. Used 0.110 x 321 = 35.31kw.

- I am assuming this is my check of gas usage on the big flame. Am I also supposed to be checking the gas whilst heating on? Do I check for 2 mins with the heating at no.9 and 2 mins with heating at lowest number? I don't know how to get from big flame to little flame.

Cold water tests
5 sec = 15.7
10 secs = 15.7
20 secs = 16.2
30 secs = 16.7
35 secs = 16.4
40 secs = 16.4
50 secs = 16.7
55 secs = 16.6
60 secs = 16.5
65 secs = 16.8
70 secs = 16.4
75 secs = 16.4
80 secs = 16.4

Hot water test
5 secs = 17.2
10 secs = 16.9
15 secs = 29.3
20 secs = 30
35 secs = 33.3
40 secs = 37
45 secs = 39.9
50 secs = 42.6
55 secs = 44
60 secs = 45.3
65 secs = 46.2
70 secs = 46.9
75 secs = 47.5
80 secs = 47.7
85 secs = 48.3
90 secs = 48.5
100 secs = 48.9
105 secs = 49
110 secs = 49.1
115 secs = 49.3
120 secs = 49.4
125 secs = 49.4

If I have forgotten something, I am sure someone will be along to let me know.

fluff

 

[DP]

Fluff, this thread is a revelation for me too. I am surprised to learn my condensing combi Vaillant super duper Ecotec 831 is no faster than your boiler.

I know the gas rate on my boiler is spot on, flow rate is as set at the factory, and my boiler is about two years old.

I clock the cold water at 17 and a minute later the temperature on hot water pipe was same as what you recorded. Therefore, it would be safe to say the HW side of the boiler and primary loop is clear of obstructions.

Heat input for your boiler is 34kwatt according to the data badge. At that figure, it has to be full flame for two minutes else gas consumption would have been less.

12l per minute is a little too much water passing through the Hot water heat exchanger. Data badge says 11.7 (for 28kw I thought the figure would have been 10.8 but am sure someone else will be able to confirm that)

Now we are back to radiator circuit. Can you take a picture of the vent on top of the radiator. In particular, what I am looking for is a vent that can be removed to allow connectiobn of a hosepipe in place of vent.



My apologies- burner neon is B that stays on when burner alight. I said A neon.

 

[fluff29]

Hi DP

Don't like the sound of connecting a hose pipe. I can't see my hubby going for this.

I'll attach the pictures anyway.

View media item 25748 View media item 25749
My husband wants to get someone in to repipe the prob rad in 10mm and get the system cleansed, flushed out.

Do you have any ideas on what the problem could be?

What niggles me is that we have the boiler at 7, and yet the big rad doesn't heat up. Even if I turn the TRV's off on all other rads, the rad still doesn't heat up. Will we ever get to the point of being able to turn the boiler back to about 4 - 5 or is this boiler not designed for this?

thanks
fluff

 

[bluey831]

My husband wants to get someone in to repipe the prob rad in 10mm and get the system cleansed, flushed out.

fluff

Hubby might be on to something here fluff ...catch him while hes hot .. so to speak!!

From my very simplistic perspective, if there is sludge in the system then it needs shifting. It might not be the cause of your existing problem but it will probably be the cause of some future problems. If on the other hand it does solve it then hey bingo!! I got sludge in my system and while I'm not really wanting to fork out dosh to have it done, even stupo like me knows its for the best. If I get it flushed I will also get the Magnafilter.

To be honest, I'm kinda wondering if this one will get solved before the thread reaches 20 pages!

 

[fluff29]

bluey

I don't think I have sludge in the system. Water quite clear when i did bucket test, and when the 6 rads were replace, plumber said water was very clear considering age. Don't know if high amounts of fermox helped.

If I can get a solidish suggestion then I will do it, but as i said previous, local plumbers don't even listen to me or look at system.

ChrisR - looking back at one of your previous posts, you said DHW heat exchanger should not get hot. Was the temp. of 42 ish that I gave you classed as hot.

fluff

 

[DP]

Fluff, if you can email me, will explain how the boiler works. Email in my profile. Have sent couple of messages to you but these seem to have been overlooked.

If you look at the two excellent colour picture posted by Chris, you will see the flow of water during HW delivery, on the right.

Left shows what happens when water goes to the radiators. I suspect the blockage is left of '3' (painted red) in drawing on the left.

What I was going to propose was to turn all the radiators off at the wheelhead on the radiator valves and both sides new radiator that is poorly heated. Remove the bleed nipple fitting and replace with 15mm coupler and a length of pipe one end connected to coupler and other in a bucket, outside or wherever water can drain away safely.

Now open the wheelhead on the rad valve while someone mans the filling loop to maintain flow of water from pipe end. For sake of experimentation, you could collect outflow for say 10 seconds.

Close filling loop valve and close the wheelhead rad valve. Repeat above test by now opening the lockshield valve. You should get the flow through the rad valve that will be the same as above if no blockage.

What you will be achieving by doing as suggested above is (left drawing by chris again) prove pipe from filling loop, through the main heat exchanger, through the diverter valve to the rad via flow pipe to new radiator via flow pipe and between filling loop and the said radiator via the return pipe. You will also be able to check the manifold for blockage.

Bucket test earlier does not guarantee water will be passing through a restriction as alternative clear path would be allow good flow of water.

Do not start re-pipeing as blockage may not be in the pipe you are intending replacing. Reminds me of the time when I repaired a TV. While I had cured the original fault, the TV kept going to standby. The good lady told me to get rid of the TV. I cut the mains cable to later (after the TV was long gone) find poor connection in the plug was the cause of telly to go to standby

 

[fluff29]

Sorry for not picking up your messages. I don't think I have ever used it before. I only worked out how to do the quotes today.

I will have a look at your messages and get back to you.

Will let my hubby see your post re the repiping.

Do you do work in Perth?

Thanks again

Fluff

 

[bluey831]

bluey

I don't think I have sludge in the system. Water quite clear when i did bucket test, and when the 6 rads were replace, plumber said water was very clear considering age. Don't know if high amounts of fermox helped.

If I can get a solidish suggestion then I will do it, but as i said previous, local plumbers don't even listen to me or look at system.

When we moved here six years ago BG said we had sludge and it needed Poweflushing. At £600 - I said no thank you kind sir They still maintained the system and a few years ago changed loads of parts in the boiler as it was having a real wobble - or they did not diagnose it properly! Either way the system works reasonably but the rad in living room does not heat up proper etc. and we've never really had sufficient comfortable heat in the living room.

A few weeks ago I had BG in to change some valves. He changed four of five and showed me the water in the tray. It was totally black. I know that dont necessarily mean sludge for sure but to me it dont look none to good.

We dont really want to go through another winter with insufficient heat so thats why I'm biting the bullet. I understand your position not wanting to fork out on something that might not solve the problem. However, I think you are probably trying to hard to get a definitive source - great if you do find it but at what point do you call it a day.

As for the plumbers or engineers coming in to sort it - there is a balance. You need to let them know you possess somewhat considerable intelligence which you have clearly demonstrated on here. However, a step too far and you are in 'their' territory and they see it as being told how to do their job - result is they will likely scoot. The ones that don't might not be worth having.

I know you don't want to pay them to do tests you have done etc - perfectly understandable. However, an engineer doing a test that you have done will be doing it with a professional eye. They are more likely to see something that you have missed - if there is something there.

 

[ChrisR]

Ya don't give up, do you!

THe DHWHE getting up to 40 odd. Not ideal but I'd say it's not a problem unless it's HOTTER than the return pipe.

Gas rates etc
34-5 kW is too bloody high!! If you look at page 3 it's meant to be max 28.4. That needs attention. The higher output 28kW boiler has a larger heat exchanger... engineering to bridge, "I dunno how lang she can tekkit, Jim."

MOdulation - reducing the flame.
On CH the boiler is supposed to light at "ignition rate" and ramp up over a minute.
ALso the gas rate should drop from max as the sensors heat up in the boiler.

The HW operation is easier to check, to see that the gas valve is at least capable of turning it self down.
Turn a tap on low, about 3 litres a minute, (pint in 10 seconds).
See if the flame stays on, or does it go on-off all the time. Check the gas rate a the meter. It should be the lower end, something like 10kW.
You can time it for 1 minute, it'll be accurate enough. So you're looking for about 15 of the small units on the meter, in a minute.

Righty hoe.
Now with the heating on, if it starts at 35kW, it should drop quite quickly.

Working with, roughly roughly
15 counts/min =10kW
30................= 20kW
45.................= 30kw

The movement of the dials on a meter is uneven, but I mean if it moves 5 counts in half a minute, it's sure as eck modulating.


By the way a boiler fixer would be able to check modulation in a couple of minutes, by disconnecting a wire...

 

[DP]

Chris, I thought the boiler was 28kw appliance.

 

[fluff29]

Hi ChrisR

I have a CB28X. Says on page.3 max. for DHW is 34kw. So think it is right, give or take my timings/where the dial was slightly mid number.

Also flow rate is 11l at 35 c rise, I am showing 12l. Does that make too much difference?

Will try the modulating on CH tomorrow night to give you/DP some more info.

I think we will probably go with getting DP to look at it. At least he seems to understand what is going on.

thanks again

fluff