Grundfos Alpha 2 15-60 130 Setting?

[woodpeckerx]

Open vented system? with feed&expansion (small) tank in the attic, check that its "full". possible blockage in the cold feed where it joins the system.

Yes, vented system, tank in loft all ok, drained it recently while fitting all the new rads / valves / ABV etc. Cold feed all ok only refilled system on Monday. Don't think the system has any bleed or bottle air vent that I can find.

Any zone valve on the system?.

S Plan system with CH and HW motorised valves.

suggest final test (tonight) just open thje ABV fully with pump on full speed 3 and note power then full open on CP1, again note power.

Will report back tomorrow or mrs will shoot me

 

[Johntheo5]

Must finish off my bottle of Jamesons

For tomorrow..
Was/is the system clean including F&E?
Have you a close coupled system, vent and cold feed, from the boiler, vent then cold feed then the pump?
What mode/setting pump before mods?
Did your system work OK before mods?

Good night.
John

 

[woodpeckerx]

suggest final test (tonight) just open thje ABV fully with pump on full speed 3 and note power then full open on CP1, again note power.

CP1 difficult to tell if there is a change with ABV open shows 16W when closed either 15W or 16W though.

On fixed speed 3, 40W ABV closed, 42W ABV Open

Was/is the system clean including F&E?

Some of the ripped out lower radiators had a small amount sludge, one of the old 30+ year old TRVs was a bit sludged up, magnetite filter was quite clean. F&E tank was quite clean, the cylinder must have been replaced in 2021 or later as it has a Jan 21 manufacture date on it. The F&E tank and cold water tank in the loft both look quite new.

Have you a close coupled system, vent and cold feed, from the boiler, vent then cold feed then the pump?

Boiler is in a utility room downstairs, massive feed pipe larger than 28mm (not measured it), 2 return pipes 22mm and 28mm. Pump is upstairs next to cylinder, the large feed pipe after routing around the garage and into the kitchen goes vertical to a T reducing to 28mm with a 22mm straight up into the loft, centre of the T is 28mm, after a short distance a second T with another 22mm pipe up into the loft. It then elbows downwards and the pump is mounted vertical, below the pump is a T with the CH and HW valves.

What mode/setting pump before mods?

Not sure, when boiler was serviced (not sure guy new what he was doing) he whacked it onto fixed speed 3 and said that will get the water round quick.

Did your system work OK before mods?

System wasn't great, the radiators looked ready to fail, a few valves had slight leaks and looked a bit scaled up, it had 1970s style skirting radiators downstairs, we got some heat from the system but I didn't check if the boiler was short cycling like it is now.

As I thought the system was finished I added a bottle of Fernox F3 cleaner on the last refill which I was planning to circulate for a week before adding the inhibitor.

Any thoughts? I'm still hearing gurgling and bubling but no air coming out of rads.

 

[Johntheo5]

The best case flow at the moment on full speed is ~ 8.3LPM, with a full open ABV should be ~ 20LPM at least.
If your boiler min output is 18kw then the dT is 31C, dont know what the flowtemp setpoint is but assuming the burner trips at 80C then this will happen when the return reaches 49C and much lower if the cut out flow temp is lower. The rads, assuming flow/return of 75/44C will only output 74% of their rated outputs leading to more boiler cycling.
Can you show a rough sketch of the system showing the ABV location etc.
The bubbling/gurgling may be caused by the system cleaner??, the system refilled OK so cant be a cold feed blockage.
The piping seems very large diameter for a fully pumped system, are there only two pipes coming off the boiler (flow&return) or are there 4?
Do you know what the boiler flow temperature is?

Also open the mot. valves fully a few times by using the manual lever.

Really can't suggest anything more constructive except to run the pump at full speed for now and maybe add another bottle of that magic cleaner for a week or so.

 

[woodpeckerx]

If your boiler min output is 18kw then the dT is 31C, dont know what the flowtemp setpoint is but assuming the burner trips at 80C then this will happen

The boiler can modulate down to 6.3kW according to the manual.

The boiler only shows water temp, I see it rise rapidly to around 50-60C then it seems to decide that rate of increase was too high so cycles off for a few minutes.

With the ABV open the boiler doesn't cycle like this, the temp moves around between 50 and 70 and the boiler fan speed goes up and down but it doesn't shut down, sounds like it runs properly. HW runs like this as well.

The ABV is Teed between the pump and the CH/HW valves, the downstream side is Teed into the return after the cylinder balancing gate valve.

The boiler has 1 flow and 1 return, the flow is 35mm and reduces to 28mm in the airing cupboard. There are 2 returns, 28mm and 22mm that join by the boiler.

Boiler flow temp is set to 70C

 

[fixitflav]

Do you actually have a problem? I've always just run the pump at the lowest speed which works OK. It's been fine so far.

 

[woodpeckerx]

Do you actually have a problem?

Yes, with CH on the boiler short cycles so the rads are taking ages to get any heat, the boiler runs for a minute or so then cycles off for about 5 minutes.

 

[fixitflav]

Yes, with CH on the boiler short cycles so the rads are taking ages to get any heat, the boiler runs for a minute or so then cycles off for about 5 minutes.

OK. Is it a new complete installation, or new pump or boiler? Or has the problem only started recently, on an existing set-up?

 

[Johntheo5]

The boiler can modulate down to 6.3kW according to the manual.

The boiler only shows water temp, I see it rise rapidly to around 50-60C then it seems to decide that rate of increase was too high so cycles off for a few minutes.

With the ABV open the boiler doesn't cycle like this, the temp moves around between 50 and 70 and the boiler fan speed goes up and down but it doesn't shut down, sounds like it runs properly. HW runs like this as well.

The ABV is Teed between the pump and the CH/HW valves, the downstream side is Teed into the return after the cylinder balancing gate valve.

The boiler has 1 flow and 1 return, the flow is 35mm and reduces to 28mm in the airing cupboard. There are 2 returns, 28mm and 22mm that join by the boiler.

Boiler flow temp is set to 70C

The cylinder balancing gate valve is on the cylinder coil return?.
Its strange behaviour that the temperature fluctuates so much with the ABV presumably fully open? as the flowrate should be quite steady.

The flowrate with the ABV closed is (40W) 5.83LPM, if the boiler can modulate to 6.3kw then the dT is 15.5C, however the problem/challenge with gas boilers is that they fire up at anything up to 65% of their rated output (not 65% of what they are range rated to) so your boiler may be firing initially at say 18kw (dT of 44C), some boilers then modulate down fairly rapidly, maybe 20/30 secs, others take a minute or so.
What may help even though theoreticall doesn't affect the ignition (firing up) settings is to range rate the boiler (if you can do it from a menu) to say 10kw and see if this is any help in getting the boiler away.

 

[woodpeckerx]

OK. Is it a new complete installation, or new pump or boiler? Or has the problem only started recently, on an existing set-up?

System I've inherited when I bought the house a few months ago, some rads were probably circa 40 years old.

To summarise:
British Gas 330 boiler, circa 2006, serviced and seems fine.
Pump Grundfos Alpha 2 15-60 130, date code of PC 1806 which I assume is June 2018
All rads replaced with brand new, 13 rads plus 2 towel rails.
All valves replaced with Drayton TRV4 auto balancing, valves were run on the factory calibrate setting (wide open) then adjusted for dT20, boiler was short cycling so Drayton said try dT15 setting but its no different. Got the impression Drayton didn't have a clue anyway. All lockshields are set to full open. All TRV heads are removed (pins up).
There was no ABV so I fitted a Tower ABBV1 to bypass from between the pump output and the CH/HW valves to the return. I believe some sort of bypass should have always been fitted even if a manual one, but it didn't have one.

HW seems fine, CH causes boiler cycling and occasionally has given an F26 flow warning also a couple of full trips with red light on.

It seems to me there is not enough flow through the CH so the boiler heats too quickly and cycles, manual states min flow must 774lph.

I think there are 3 possible things left now, the pump but it seems fine for HW? The valves themselves, maybe these autobalancing valves are the issue or I still have air trapped somewhere.

 

[Johntheo5]

System I've inherited when I bought the house a few months ago, some rads were probably circa 40 years old.

To summarise:
British Gas 330 boiler, circa 2006, serviced and seems fine.
Pump Grundfos Alpha 2 15-60 130, date code of PC 1806 which I assume is June 2018
All rads replaced with brand new, 13 rads plus 2 towel rails.
All valves replaced with Drayton TRV4 auto balancing, valves were run on the factory calibrate setting (wide open) then adjusted for dT20, boiler was short cycling so Drayton said try dT15 setting but its no different. Got the impression Drayton didn't have a clue anyway. All lockshields are set to full open. All TRV heads are removed (pins up).
There was no ABV so I fitted a Tower ABBV1 to bypass from between the pump output and the CH/HW valves to the return. I believe some sort of bypass should have always been fitted even if a manual one, but it didn't have one.

HW seems fine, CH causes boiler cycling and occasionally has given an F26 flow warning also a couple of full trips with red light on.

It seems to me there is not enough flow through the CH so the boiler heats too quickly and cycles, manual states min flow must 774lph.

I think there are 3 possible things left now, the pump but it seems fine for HW? The valves themselves, maybe these autobalancing valves are the issue or I still have air trapped somewhere.

Can you just note the watts in CP1 & full speed modes while on HW only, ABV Shut.

 

[woodpeckerx]

The cylinder balancing gate valve is on the cylinder coil return?.

Yes its on the 22mm out of the bottom of the tank coil, its set wide open although I think I read cyclinder balancing is now banned by building regs as the programmer should have separate timers for HW/CH that can be offset in time so no balance required.

Its strange behaviour that the temperature fluctuates so much with the ABV presumably fully open? as the flowrate should be quite steady.

I think it ramps up and down then stabilises when ABV open or when HW is on.

What may help even though theoreticall doesn't affect the ignition (firing up) settings is to range rate the boiler (if you can do it from a menu) to say 10kw and see if this is any help in getting the boiler away.

The boiler has no menu, its only got on/off, water temp display and a water temperature knob. These boilers seem to have a max rating of 31kW but come from the factory pre-set to 18kW, AFAIK this one is still set to 18kW, it has a sticker on the adjuster pot saying 18kW.

 

[woodpeckerx]

Can you just note the watts in CP1 & full speed modes while on HW only, ABV Shut.

Readings on HW only

CP1 15/16W
CP2 26W
III 39/40W

 

[woodpeckerx]

I also checked fixed speed II on HW only and this reads 15W, doesn't this mean the flow is still very low looking at the graphs?

 

[Johntheo5]

Yes, very low flowrates.
CP1 at 15W, = 1.7LPM
CP2 at 26W, = 4.83LPM
CC3 at 40W, = 6.3LPM
Flow is prop to the sqroot of head so CP1 at 3M should flow 4.83*Sqroot(3/4.5),
3.89LPM and CC3 at 6M should flow 4.83*Sqroot(6/4.5), 5.6LPM.
Wonder if this pump is now suspect, if you are confident you could remove the complete head and check the pump ports and impeller vanes for crap, if you have the pump isol valves with a spindle that you shut with a adjustable spanner then no problem with leakage but if they are the ball type with a allen key shut off then almost guaranteed to leak.

This may be of some interest, from someone with 10 rads + HW cylinder. System in excellent condition with F&E Tank.(same, Alpha 2 Pump).
CH only, CP1, 22W = 13.3LPM.
HW only, CP1, 25W = 17.5LPM