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

[tamz]

How many people giving advice on this actually installed microbore systems for a living?

I've installed 1000's~~???????? don't know how many. A couple nearly every week from the 70's right through the 80's.
I don't care what anyone says or what is in the books a radiator that size will never fully heat on 8mm unless the pipe runs are minimal. I as most others who installed them learned that one within weeks of first doing it.

Repipe the rad and also consider repiping the other couple of big bedroom ones. 10mm copper will be fine but 15 will be better. Don't be tempted to use 10mm plastic.

As said before i'm pretty sure it is an FEP job (manifolds pics). They were the dross of systems to begin with. 8mm pulled halfway around the house.

 

[Agile]

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."

Chris was having a senior moment and forgot that your boiler is not 100% efficient and that to produce 28kW has to consume 34kW.

But he did not forget ( as you did! ) that you have not done the second part of the test at mimimum power to see if its modulating.

Set the boiler to 3 li/min and turn the temperature control down as low as you can whilst still keeping the flame lit.

Tony

 

[DP]

Tony, what is the purpose of carrying out the test at low burn as you describe? How will that help to locate the fault? Also, how do you ensure the burner will not go out and how does Fluff ensure flowrate is 3l constant? What apparatus does she use to verify this precise flowrate? Setting the flowrate low will not guarantee burner will peg at low burn, it can go to high flame and equally shut down when the heat produced by main heat exchanger is not used up. 2 minute burn to do gas rate on E6 will be shambles as end result will be as usefull as chocolate oven gloves.

I do not think Chris had a senior moment- he thought the boiler was 24kw model.

Tamz, we are not talking poor circulation as in not suffiucient water flow due to pipe length and bore but poor circulation (I suspect) due to partial blockage someplace. FEP instals were poor, but rads still heated. Most rads in Fluff's house do not heat as avarage temp difference is 30 degrees.

 

[ChrisR]

Chris was having a senior moment and forgot that your boiler is not 100% efficient and that to produce 28kW has to consume 34kW.

If you'd read what I'd written or looked at the manual you'd have seen I was comparing withthe 24kW boiler figure and I also referred to the "Larger" 28kW boiler.

35.3 iss still abit high - I'd turn it down to be below rather than above the MI figure on an oldish boiler.

My suggestion of making the flow 3litres/minute at the tap was to see if the gas valve is actually capable of contolling a lower gas rate. We've all seen them maladjusted so the minimum is barely any lower than the maximum.
It's possible that the CH control is misbehaving and the HW one isn't but I'm sure that's less likely.


Tamz - no not as many as you and never installed on 8mm though I've see a few! 10mm plastic seems to be slipperier, used that latterly and had no problems. Haven't had flow problems on 8mm systems that weren't blocked solid, either tbh. Balancing I've found quite critical though, an i-r thermometer makes all the difference. 8mm does sound too small (do we know how long the feed pipes are??) but if the darned boiler would stay ON a bit longer, it would have a decent chance.

To be honest this thread's got so long now it's hard to find things, it's too much effort for what would all be over in an hour on site.

 

[fluff29]

DP - what makes you think that there is a blockage at the diverter? Really hot water flows away from the boiler down the red pipe, therefore can't understand why the water would get stuck at the diverter? I would have thought the the blockage would have been further down on the flow or on the return somewhere.

ChrisR/Agile - I will be trying the low gas tonight. Did not get the time last night after you both posted.

fluff

 

[tamz]

This post has gone on so long a few points have been lost and things made worse with differing advice.

Page 1
Originally the problem was a rad not heating properly. The system is pretty clean.
The rad was new and had been changed from the original single to a double 600 x 1600 K2 The original K1 worked. Pipes undersized
The other couple of rads that were slightly cooler at the bottom 1/3rd were the 11 and 12 K2's. Pipes also borderline sized.

The original advice was it was sludge, choked needed balancing etc!
The balancing advice was followed.
Microbore (8mm) systems only ever require minimal balancing if any

At the moment the water is going nowhere fast as the balancing has probably restricted the flow and circulation so much the boiler is not being given a chance to work properly.

Unbalance the radiators and get the big one repiped then see how the boiler works.

I agree Chris. It could be diagnosed properly by anyone with half a brain and a bit experience actually seeing the job.

 

[DP]

The the lockshield and rad valves are fully open, flow and return temperatures would not be as shown in the following data

*Boiler - Flow F87.8 Return R43.7
*Kitchen - F79.3 R49.7
*Dining Rm - F81.9 R41.9
*Living Rm - F84.0 R50.3
*Bathroom - 80.3 R74.5
*Hall - F82.2 R49.1
*Daughters room - F80.7 R56.0
*My room - F79.7 R51.3


I agree, microbore is just about self balancing, but still, use of dual thermometer to check differential cannot do any harm.

Fluff. My reasoning that blockage is at the diverter is based on similar calls and also assumption that lockshiellds are fully open i.e. no additional restricition is in place at the radiators. If you look at two diagrams, follow the 'red' water through during hot water demand (right drawing) based on latest data you posted, it has to be said the main heat exchager output is used up by the hot water heat exchanger (boiler does not modulate nor does it go out)

When boiler is in CH mode, water will now flow through the pipes that are coloured blue (right drawing). It is flow to flow and return pipes that is causing the boiler to heat primary water and then go to sleep (does not happen during HW run test). It is a matter of now locating where the restriction is. If restriction is at the lockshield valves becasue they are closed, opening these will be a good idea. If new rad is oversized for the 8mm microbore pipe, then obviously replacing the pipe might be a good idea. But, looking at the flow and return data, I would be looking for restriction instead of going the plumbing route just now.

 

[fluff29]

I HATE MY HEATING

Put DHW to 9, ran tap at 3l a minute. Boiler stayed on big flame except when it got too hot and cut out, re-lit after a few seconds.

Boiler only ever stays on big flame when CH is on.

Tryed in on no. 3, 4 and 7.

no.3 - stayed on for 1 min
no. 4 - stayed on couple of mins
no.4 - stayed on 1 min
no.4 - on 55 secs = 0.026 gas used
no.4 - on 41 secs = 0.019 gas used

At this point, thought I would try Tamz idea. Opened all lockshields. All smaller rads piping hot, 2 big bedroom rads did not heat fully. Big prob rad did heat fully (as normal).

Put boiler to no. 7
Ran 10.20 mins - used 0.311 gas

The boiler did not at any point modulate during the above CH test. It stays on big flame then just cuts out for 3 mins.

Are we back to a modulation problem??

Was of the mind tonight to just get the big rad repiped but I have a niggle of why does the boiler cut out still when things not fully warm?

I have managed to get the bedroom rads to heat fully when system balanced, yet when I open up all lockshields, they do not fully heat up. Therefore I think the balancing does work.

If I got the big rad repipe, got system balance properly, I still think the boiler will still cut out. I am running this huge boiler at no. 7 and it doesn't stay on long. I should be able to turn it back to 4 or 5 and it should stay on long enough to heat the rads but it doesn't.

Does anyone understand this?

Should I turn the big rad off and run the boiler on 4 or 5 to see how long boiler stays on. This would take this rad out of the equation and surely the boiler should stay on long enough to heat all other rads as we get heat to them? Is this logical?

fluff

 

[D_Hailsham]

Could be a knackered Pump!

Another possibility.

Reading back, I've just realized that it can't be a knackered pump as Fluff had it replaced. See this post.

 

[fluff29]

Couldn't get no internet connection earlier, tryed to do the modulating on CH from memory and got it wrong.

I have now ran tap at 3l minute. Have tried the boiler at 0.5 intervals from 3 up to 9. The boiler does not modulate, it just cuts out.

fluff

 

[DP]

Fluff to check modulation, you need monometer.

See your PM box later. will send you text explainging what modulation is. If you already know, then just ignore the PM.

 

[fluff29]

Thanks DP

Just been making tablet, so I will now overdose on a sugar high whilst waiting on further info.

 

[Agile]

Tony, what is the purpose of carrying out the test at low burn as you describe? How will that help to locate the fault?

I do not think Chris had a senior moment- he thought the boiler was 24kw model.

Danny, we need to know first if the full power is correct.

Then we also need to know if the minimum is correct.

The OP has confirmed the full power is correct and has said the boiler always remains on full power and just cuts out when it gets too hot.

If Chris did not have a senior moment then he was replying without having read through all 16 pages of previous postings. It would be far easier to have a senoir moment!

Its probably a wrongly adjusted gas valve but will need a competent engineer to check and correct.

Only then can we start to consider the flow restriction aspects which seem to be the other/main problem.

The temperature differential measurements indicate the bathroom rad needs to be closed more as its short circuiting the flow.

Tony

 

[D_Hailsham]

Fluff,

What number are the TRVs on your rads set to?

 

[fluff29]

Hi DH

All TRV's are set to maximum. The house never get warm enough to have them lower.

The only exception to this is my bedroom. As the rad was doubled up, it does get warm. When I had the heating on low during all the snow in Dec/Jan (was on at no. 4 24/7) my bedroom got a little hot, but not too bad.

Which reminds me, when it was very cold last winter, I had my heating on all the time at 4. At this point the upstairs of the house was comfortable but the living room never got above 20.

Agile, would a wrongly adjusted gas valve stop the boiler from modulating and keep the boiler on full all the time. If it is advisable to get a guy out to check this, should I just get the prob rad repiped at the same time to eliminate this?

I have never seen the boiler switch to a small flame either on hot water or heating. Does this lead back to DH's original theory on the boiler not being able to modulate low enough?

Fluff