Vaillant Ecotec 438 showing code S53

[properjob70]

Hi,

Came back to a cold house (digs) last night and the radiators were lukewarm. It's an old house and loses heat like it's going out of fashion so needs warm radiators. The CH temp on the front of the boiler is set to 75C and the radiators are probably reaching about 40C.

Cracked a couple of the bleed valves on the radiators upstairs and no air up there. So after a wrestle with the Vaillant manual had a look at what's going on on the boiler panel and found code S.53 showing "Appliance is within the waiting period of the operation block function due to water shortage (VL-RL spread too big)".
So that kind of diagnoses what's wrong (though with the system showing low water I'd have expected there to be some air in the upstairs rads). Can't find the fill loop anywhere round the boiler itself though! Not sure what VL-RL is as it's not explained, but I guess low water should be cured by refilling the system?

After reading the section of the manual covering test programs, I was wondering whether it needed a fill loop at all as it's quite a whizzy boiler, so tried activating the relevant ones:

P.0 Bleeding test program. The heating circuit and hot water circuit (when accessories are fitted) is bled via the automatic air vent (the cap on the automatic air vent must be loosened).

This one flashed up "HP" when activated and nowhere in the manual does it explain where the automatic air vent might be so I can loosen it. Nor does it explain what "HP" is.

P.6 Filling test program. The diverter valve moves to the centre position

I had assumed that this program would negate the need for a fill loop as I can't find one. When activated, the display flashes up "- bar" which I think means it's too low for it to read. Activating the test program did not result in any noises of water filling the system.

Think I've done all I can now, so any ideas?


Post the above and some googling on the VL-RL issue, I reset the d.0 part load to 28 (S.53 still came up). Reset it again to 20 and things seem to be better.

Also, went into the most recent Fault code storage and found two F.72 codes present - Flow and/or return NTC fault. Flow and/or return NTC is defective (tolerances too big). Also a F.24 code - Water shortage, temperature rise too quick. Pump blocked, insufficient pump output, air in appliance, water pressure too low

 

[lightning]

S53 indicates poor flow, Dirty heat exchanger?? is the pump set to max, has bypass been adjusted correctly!! Are flow & return thermistor in contact on the pipes

 

[properjob70]

Thanks, turning the part load setting down from its 38kWh max has stopped the code coming up so at least the house stays warm.

The landlady's gonna have to get a heating engineer out to sort it properly though!

 

[Agile]

38kW is a lot of heat!

A three bed semi usually needs 10-12 kW for heating so your house is about 10 bedrooms?

It seems likely that its seriously over sized. You can calculate the whole house heat loss if you want a bit of fun.

If I was your landlady then I would not want my tenants resetting the boiler!

Tony

 

[properjob70]

Yep, big old house (former coaching inn) with 9 rooms upstairs and 6 rooms downstairs, + quite a bit of circulation space. So yes it needs a big boiler.

Landlady (who lives in her own house) has a duty to provide me with a room warmer than 10degrees C in return for my £400pcm but faced with imminent hypothermia at 9pm last night, thought I'd suss it out for myself (lots of running up and down stairs fiddling with the boiler keeps one's cockles warm lol).

 

[Agile]

In that case if the insulation is poor then it might need a fair amount of heat but you have turned it down to 28 kW and its apparently heating OK now.

The question then comes what kind of pump(s) does it have? A single standard domestic 15-60 isn't really powerful enough.

Tony

 

[properjob70]

Yep, it still S.53'd at 28kWh so had to wind it down some more! So yes, I guess it is a bit over specified, but only the heating engineer who put it in would be able to tell me why he did that - maybe as you say the restriction's the pump hence the differential temps problem. But I wouldn't know whether it has one or two CH pumps or what rating they are - I'd be minded to find out if I suspected the pump wasn't working and I was cold!!

The room's now at the heady heights of 17deg C so it's getting warm enough.

 

[Agile]

Standard comfort is not 21C but perhaps students are meant to wear sweaters and so have lower temperatures.

If the pump is not by boiler then it may be by the hot water cylinder.

Tony

 

[properjob70]

It used to be a student place but the decor got upgraded so is now full of 30/40something divorcees!!

Now the settings have been changed so the heating doesn't anti-cycle so much, it is now apparent that some of the radiators are reaching the required temps and some aren't (this might be a balancing issue though). So I'm suspecting that there are two CH circuits/pumps and one's working but the other isn't. I haven't managed to find the CH pumps. The HW has a big high-pressure booster pump to give us hot water at a decent pressure - that's located by the hot water tank, but not the CH pumps.

When the heating kicks in the CH water temperature shoots up very rapidly and then the "cycling" symbol starts flashing. That makes me think there is not enough flow through the boiler so it's cutting out to avoid damaging the system. Other times it runs quite smoothly and holds the temperature at a constant 75degC while it's pumping. So the pump is likely working but intermittently.

I understand (from the Vaillant manual) the pump runs at two speeds and if you set the d.0 to under 60% of the boiler's rated output, the pump will never run at the higher of the two speeds, so adjusting the d.0 setting has made it run at the slower speed. When you set it where it will run at the higher speed the problems are immediate.

For info the main thermostat is in the downstairs hallway away from any radiators. The ones in the other end of the downstairs hallway are not getting hot anyway. So the system is never heating the house enough to reach the thermostatic cutout point before something else cuts the heating off.