ECOTEC 418 HW causing S53/S07/S08, sizing, VR66

[rbranco]

Ecotec 418 open vented
S-Plan
2 Port HW & CH Valves
Standard HW/CH timer and roomsat/cylstat
Pump 15/50 - Speed 3
ABV installed (setting 2) between pump/valves and return back before the Magnaclean but its on a 15mm not 22mm pipe
10 Radiators (6xType10,2xType20,1xVertical double column, 1xType11
CH Temp 75c
Magnaclean Pro
Old 1910 house with solid walls, insulated loft to 250mm (not in kitchen extension)

Ive got an old thread which was related to this annoying boiler, issues come and go.
https://www.diynot.com/diy/threads/vaillant-418-s53-s7-after-new-radiator.496679/

In recent months as its got colder ive noticed system low firing on S53 especially when HW/CH is being demanded at the same time or when the system starts up from cold, as it gets hot it can go to S07 as the out water temp goes over set point but does not scale back quick enough.
The S07 has been a long standing issue as it can also happen on HW.
Ive scaled back D00 from 16 to 10 and S07 is not such a big problem any more until the whole system comes up to a flow diff temp of about 25c then its rising too much anyway.

Magnaclean has not been too dirty other than when initial powerclean was done back in 2017/18.

Its hard to get the house temp much over 19/20 and takes a long time to get there from cold which based on rad outputs seems to indicate its on the limit of output and will need some rads to be be sized up.

After reading lots of threads im considering the following.

1. The system needs a clean, MC3 etc for a few days, heat exchanger may be sludged then redose MC1
2. Install VR66 to give HW priority control for boiler firing
3. Replace a few of the Type10 radiators for Type 11/21/22 space dependent. They are over 25 years old (when I first moved in, not sure when prior owners had them installed but ile say add another 10 years on that, first powerflush removed tonnes of crud from them). Some places the size makes no sense, ie the hall is huge as it its length of the house and open right to the top but its got a really tiny radiator (7m long, 8m+ to top and 2m wide)


Below is my calculations based on Type10/P1 figures that stelrad show, does not account for age/corrosion/paint emissivity as prior owners have painted rads etc. Silly me its the first time ive actually done the calculation in all these years, I always suspected it was low due to age of house and nearly all type10. The upgrade of one radiator in 2018 actually pushed the BTU up for that room by 2k.

Anyway my real question was, is there any way the VR66 can be used with standard timers or would it need a VRT350/VRC700 to control it.
Its not well documented but if there is no eBUS timer/roomstat etc connected what does the system default to?
If it defaults to just looking at flow temp and cyl stat and also the boiler trigger, it would be possible to loop in series the CYL stat connection in the VR66 to the manual timer and the boiler trigger would be that of the CH again to the manual timer?
Ive also seen someone the use the HW valve grey/orange wire as the CYL trigger instead of it currently being tied to the CH valve and triggering the boiler.
Only thing with this method seems to be that it can not do priority by shutting CH unless you give all that control over to the VR66 but if you do it seems that you may have to go full eBUS controls.
https://www.diynot.com/diy/threads/vr65-vr66-for-hw-flow-temp-control.494071/


If none of that is possible ile just dive in and get a eBUS timer and replace all the drayton controls.

Any more info im happy to provide.

Thanks in advance for help.

 

[picasso]

I would fit a 15/60 before anything else and put the hot water timed to come on when the heating is off.

 

[rbranco]

I would fit a 15/60 before anything else and put the hot water timed to come on when the heating is off.

Ive always been thinking if pump should have been a 15/60, its always been UPS 15/50 since ive lived here.

In the morning the HW is on at 630am about 1h before CH, but as ive set D00 to 10kw this limits its its recovery speed.
In the evening they can be on both at the same time and that is the main time it can trigger S53 and then its on low fire for quite a long time, this cold weather has increased its chance to do that.

Note house is occupied 24/7 due to elderly parent so heating is on all day from 730am till 1130pm between 19/20c then outside these hours is 16c.

 

[Gasguru]

Where exactly is the bypass fitted...it should be from the pump outlet to the return such that the water is continuously flowing in a loop.
You might want to try opening it up ie. setting it even lower in order to achieve a 15 to 20 degree drop across the boiler flow and return.
Is the pump wired directly to the boiler (ie. controlled by the boiler).
Are the rads properly balanced so they all heat up evenly?

 

[rbranco]

Where exactly is the bypass fitted...it should be from the pump outlet to the return such that the water is continuously flowing in a loop.
You might want to try opening it up ie. setting it even lower in order to achieve a 15 to 20 degree drop across the boiler flow and return.
Is the pump wired directly to the boiler (ie. controlled by the boiler).
Are the rads properly balanced so they all heat up evenly?

Yes it's installed after the pump and before the valves and returns back just before the magna flow. I had to insist the original installed put that in as per spec, but he put 15mm return pipe and I suspect this causes issue as main flow pipes are 22.
I've had the ABV set at 1, but it does not help that much when all the rads are open.
Yes pump is under boiler control for overrun.
I've adjusted many radiators down to help balance the system and it's better but the biggest problem is when HW/CH demand happen at the same time as it does not take advantage of the larger boiler size due to d00=10.

 

[Gasguru]

What temp are hou getting across the boiler flow and return

 

[rbranco]

What temp are hou getting across the boiler flow and return

Well that depends if its in CH Only or CH/HW or HW only.
In CH only ive got it to be 75/50, but any higher return it will may start to trip out when flow temp goes over to set point and it can not scale back quick enough.
But in CH/HW you can get 75/35 for quite a long time on S53, problem you have when it gets into that position is that it gets into a low fire mode for a certian time, water temp drops, then it eventually fires up but after a set time return flow does not reach correct differential then it goes into low fire again, rinse and repeat until hopefully return water temp comes up.

S-plan just seems to be a nightmare for this boiler unless you have the additional logic.

 

[Gasguru]

The boiler is happy when the flow and return difference is say 10 to 25 degrees...more than that and the boiler protects itself by throwing the S53, so your 40 degrees is indicating a serious flow issue.
I'm running the Glowworm equivalent to this model with a higher Kw and 15/50 on speed 2..it sits around 15 degree delta.
Have you checked the pump impeller torque....4mm screwdriver in the spindle under the bleed plug. You should struggle to stop it when it starts up.
Pump valves fully open.
Bypass plumbed in the right way.
How's the cold feed and safety vent connected...that's always a favorite place for debris to block the pipework.
Otherwise blockages I'd guess...

 

[rbranco]

The boiler is happy when the flow and return difference is say 10 to 25 degrees...more than that and the boiler protects itself by throwing the S53, so your 40 degrees is indicating a serious flow issue.
I'm running the Glowworm equivalent to this model with a higher Kw and 15/50 on speed 2..it sits around 15 degree delta.
Have you checked the pump impeller torque....4mm screwdriver in the spindle under the bleed plug. You should struggle to stop it when it starts up.
Pump valves fully open.
Bypass plumbed in the right way.
How's the cold feed and safety vent connected...that's always a favorite place for debris to block the pipework.
Otherwise blockages I'd guess...

I have not tested the torque, I did not know if water would just fly out if I had the cap open when it starts up.
Ile get that done and reply back, the motor is super hot when its running, but im not sure if thats not just conducted heat from the water.
Pump valves were replaced a few years ago from gate to ball due to them snapping off head, yes they are open.
ABV is going correct direction with arrow on body.

I know there is no air trapped on the HW tank coil as that has a blead at the top you just open but the boiler has an automatic one and you never know if its become blocked or not so I may just crack the nut and see if air comes out.

 

[rbranco]

I checked the pump, its easy to stop it starting spinning and also when its spinning you can easy stop it with a screwdriver. But when its off its free and easy to turn.
Its an UFS1 installed when the boiler was originally commissioned more than 10 years ago.

 

[Gasguru]

Pump ball valves are notorious for leaking on the spindles as soon as they're touched...I replace them with gate valves.
I guess you mean a Grundfos UPS?
Throw a new pump at it for starters..

 

[rbranco]

Pump ball valves are notorious for leaking on the spindles as soon as they're touched...I replace them with gate valves.
I guess you mean a Grundfos UPS?
Throw a new pump at it for starters..

Yes Grundfos UPS1 (not UFS) some 12 years ago.

 

[rbranco]

Ok I think I found source of the issue, I forgot the same happened when system was last magnaclensed several years ago.
Lots of crud particles/flakes stuck in the impeller, I cleaned it all out and now it works better without the hum, but I think its been clogged up for quite a while and its damaged the pump somehow.
Its still running super hot and when I sometimes stop the impeller it will not start up again or when it does its slow then spins up but still quite easy to stop it again.

 

[ScottishGasMan]

Few things here.

1. You need a new pump, you physically should not be able to stop the impeller while its running and if you did it should kick back to full speed the moment you release it.
2. You can not run any condensing boiler on those differential temps without damaging it in the long run. its designed for a differential of between 5 and 20 degrees, strangling the flow through the radiators to reduce return temperatures does not improve efficiency, having rads sized to loose the heat properly does. If you have a 40 degree temp difference through the boiler at 10kw then your running approx 1/4 the flow rate that this boiler needs, and also brings me to point 3
3. that the bypass cannot be set right as if it was it would allow more flow through the boiler keeping the temp difference across the boiler correct (assuming the pump was working at full power-but Id imagine it may still need opened a little after)
4. If you are flushing, use MC5+ and before adding it to the system remove the plastic sleeve off the magnaclean magnet and leave it aside, the magnet will pick up way more with that off and its much easier to clean off with a paper towel, which you should do a few times a day for the period that the cleanser is in the system.

 

[rbranco]

New UPS3 pump fitted (constant speed 2)
Drained and refilled with 1 bottle of Fernox F3
Boiler d0 increased to 16 and max flow temp of 70
ABV set to 4

Now it is less likely to trip out and it modulates down before temp over shoots when in CH. Return slowly rises up to about 52 then stays stable like that at the moment.

My VR66 will arrive this week hopefully and then it should help with the HW.

Will eventually change a couple of undersized radiators so it will increase KW of system to also help with the overall speed house heats up initially.

Ile dump the F3 out in a couple of days, clean magnaclean and refill and add F1.