Bypass Valve still flowing when fully wound down

[ChrisNason]

D0 shows it set to 14kW

Now compare that to the total of your rads using Stelrad Elite Catalogue to see if they are similar.

d40 = 53c; d41 = 43c 10C differential

After 2 minutes: d40 =67c; d41 = 43c 24C differential

4 minutes: d40 = 67c;d41 = 45c.22C differential

The flow temperature is probably set to 67C. Is the temperature control on the front of the boiler set to max or something lower?

At 14kW output the max flow rate should be 10 litres/min (0.6m³/hr; 0.17 litres/sec. Depending on which speed you have the pump set to, the head will vary from about 3m to 5m. This is well within the range of your ABV.

D_Hailsham
I'll do the calcs later.

The flow temperature shows on the display panel as you move the control. So yes, I probably had the control set to 67c but there is still some movement left before maximum.

Still think the ABV is a problem (unless the system really is building up too much pressure

 

[D_Hailsham]

Still think the ABV is a problem (unless the system really is building up too much pressure

The ABV has to be adjusted when the pressure is at a minimum, i.e when all radiator valves are fully open. When the TRVs operate the pressure increases and the flow decreases. So the ABV will open to maintain the correct flow through the boiler.

 

[ChrisNason]

Right - Next Test.

Everything off except the faulty radiator (including Water circuit)

Within 30 seconds flow pipe is stonking hot and the return is hotter than it's ever been. Radiator still cool.

After 2 minutes the third of the eight panels is getting really hot, all others cool.

After 4 minutes flow pipe is starting to cool. Another minute and it's back to stonking hot.

After 6 minutes radiator starting to warm across most panels with number 3 fin stonking hot. Return still hotter than it's ever been and staying fairly even.

Flow is going up and down in temperature. I presume this is because the Boiler is not firing that often.

 

[D_Hailsham]

So you have a 14kW boiler trying to heat a 2kW(?) radiator.

The boiler lights and goes to max power; temperature rises quickly; boiler modulates down to minimum (5kW); temperature still rises; boiler shuts off; boiler waits until water has cooled down; cycle starts again.

What was the purpose of this test?

 

[ChrisNason]

So you have a 14kW boiler trying to heat a 2kW(?) radiator.

The boiler lights and goes to max power; temperature rises quickly; boiler modulates down to minimum (5kW); temperature still rises; boiler shuts off; boiler waits until water has cooled down; cycle starts again.

What was the purpose of this test?

It was one of the suggested tests on this forum

 

[Agile]

My purpose in suggesting this test is to see if the rad is indeed connected to the boiler circuit and can potentially work.

In virw of the result there seems to be no need to do the bucket test.

If we start from this situation, my next one will be to open each other lockshield just the MIMIMUM until a slight flow is felt through it.

Then repeat that with all the other rads and if done carefully and you might end up with ALL the rads working!

Tony

 

[ChrisNason]

OK. So I'll ditch the bucket test.

I think I'll also look to replace the ABV in case it's faulty. It still runs scalding hot in any of the tests I've done. It also was added at the same time as this radiator.

This morning I'll start with a crude re-balancing in line with Agile's suggestion.

 

[ChrisNason]

Still think the ABV is a problem (unless the system really is building up too much pressure

The ABV has to be adjusted when the pressure is at a minimum, i.e when all radiator valves are fully open. When the TRVs operate the pressure increases and the flow decreases. So the ABV will open to maintain the correct flow through the boiler.

D_Hailsham
I have all the rads open and the ABV set above 0.5 BAR and it's still scalding hot.

 

[ajrobb]

It [the ABV] also was added at the same time as this radiator.

It's not looking good for the ABV.

 

[D_Hailsham]

It [the ABV] also was added at the same time as this radiator.

It's not looking good for the ABV.

Seconded.

 

[MJN]

Just thinking out loud here; how is the ABV mounted/oriented? Mine is located such that its exit port gets heated by the return flow, even when the ABV is closed. It can make setting by some of the conventional methods a bit tricky(er) because it is not clear whether the exit port temperature increase is due to the ABV opening or the passing return flow.

Mathew

 

[ChrisNason]

ABV is going. I've run everything down this morning and checked the tank (which has a brown slime on it). All cleaned now but I know I've got to sort that.

When I fired it back up I bled the pump and after 5 minutes of very noisy running it's quieter than it's ever been.

But the ABV got hot at the same rate as the flow. Right down at the exit to the return it was flowing hot.

 

[ChrisNason]

With the quiet running of the pump I've turned the Hot Water circuit to 'Constant'. This means when the CH was required first thing this morning it wasn't competing with the Water. As a result I've got a reasonable performance from all radiators (and with a wind finding all the bad windows!)

The ABV is still running hot so it has to go.

I'm worried about the Feed Tank having a brown skin over it. The water underneath was quite clear. I suppose if the vent pipe was running the skin would have been broken. So, is it evidence of a previous problem?

 

[ChrisNason]

Should now be an image of what the feed tank looked like. It had a brown skin on it that could easily be removed.

This is the tank after I've taken out the first cup full of skin.

You can see it's not broken under the vent pipe so I'm assuming this has not been running.

Untitled

• ChrisNason
• 21 Nov 2010
• 1

 

[ChrisNason]

Just a thought (on the Feed Tank)

Could the system be flowing back up the feed pipe when the pressure gets too high.

There is an air collector in the system which the feed connects to.