help with ecoTEC valliant 831 and heating

[MW9]

Hi I hope someone can help with my heating which drives me crazy for the past few years, I moved in 2019 so I don't have the history how the heating was working in this house in the past year

boiler installed on ground floor ecoTEC 831 installed in 2013 according to the service papers
I have 15 radiators (3 towel rails)
3 zones
1st zone ground floor controls 6 radiators,
2nd zone controls 1st floor and loft, and one radiator in hallway on the ground floor the one with heating issue
3rd zone is the hot water tank for the showers on the 1st floor
radiators have TRV install excluding the towel rails in bathrooms

the ground floor hot water in the kitchen goes directly from the boiler, hot water tank only serve bathrooms

now the radiator in the hallway is not heating up, I try to regulate the lock shields in all radiators and when I get that it start to heat up I stop changing lock shields , next day when the heating comes the radiator is cold again and I start again... when I shut the 1st zone ground floor then the radiator in the hallway heats up

I had all sorts of engineers and the boiler have all the parts replaced including pump and expansion vessel due to some other issues losing pressure, changed motherboard as it died when we move in etc,

with the original settings it was set to:
D.000 partial load: auto
D.014 pump speed target value: Auto
D.015 the actual speed was showing as 15%
D.019 function mode of 2 speed pump: CH auto and DHW stage2
with those settings the boiler was reaching flow temp quickly and then I had egg timer and it was cutting off and it was doing it a lot

I was testing different settings and with:
d.014 set to 55%, 60%, 70% 85% or 100%
d.019 set to always stage 2
the flow temp reach desired temp and is stay there without the egg timer and cutting off , but the radiator in hallway is still not heating up

when I close the ground floor it is heating up. I tried to use x400 and clean the system, the lock shields are turn down to the point that if I close them any further the radiators will stop heating up and the one in the hallway is fully open.

the strange part is that the D40 and D41 the return temp is showing only 5deg lower then the flow temp but the pipe does not feel like it so when the flow is set to 75deg, the flow pipe is very hot I won't be able to hold it and the return pipe is only lukewarm I can hold it for hours but the d41 return stat will show 70-71 deg which is not a case as I would not be able to hold the return pipe. last year I tested return pipe with thermometer and it was much lower what d41 is showing.

is there anything I'm missing or I can try?

 

[DP]

First thing I would do is to fully flush out the x400 ( as suggested by the chemical makers)
Secondly, read up on how to balance the system- you do not understand what the function of lock shield is. To screw it down to a point where next stage is no circulation is incorrect.

Setting pump speed to lower end, no wonder the boiler temperature rises rapidly
Setting it at max, is the boiler even condensing?

You should be looking at temperature differential which is a function of pump speed and lock shield setting

 

[MW9]

I did drain the the system to flush the x400 and refill with fresh water and added inhibitor

I run initially around the house with all radiators fully open to check which one heat up first make note and tried to balance with the ones heating up first turned just a quoter and the rest opening a bit more, so I thought I will try different approach and start turning down the radiators to see which one is stealing the heat (I'm not a Plummer or heat engineer just trying to sort this out as its going for few years and I had few companies over already)

and does not matter what I do the difference in d40 and d41 is 5 degree on the LCD but the pipe temp when measured is different so I wonder if the reading on the boiler / screen is wrong and things might not work properly?

 

[Johntheo5]

If the boiler isnt cycling then the heating demand must be > 9kw, boiler minimum output.
Are all the rads heating up properly apart from 1 or 2?
the d.02 reading seems strange, dT of 5C, when the return is actually only lukewarm, these boilers have a internal bypass which comes factory set to 2.5M and is adjustable between 1.7M & 3.5M, doubt if anyone has been messing about with this but I allways think that the 2.5M is quite low, its possible that this bypass is (bypassing) so the actual boiler Hex return temp will be higher than the rads/system return but I don't think the return sensor is located after the bypass. When d.014 is set to auto then the pump speed is controlled between 70% and 100% so 15% (d.015) is actually 74.5% speed or 56% of the max pump head of say 7M which = over 3.9M so difficult to see that some bypassing not taking place but still shouldnt account for the huge difference between the actual and displayed return but it might.
If the return is say only 30C, (with flowtemp of 75C) then the rad(s) output will only be 56% of their rated output so you would need over 16kw of rads rated output to prevent the boiler from cycling at < 9kw.

Did any of the engineers test the flow & return sensors?.

Edit: See correction re pump speed and head, above. (Head is proportional to speed squared)

 

[MW9]

not sure how to tell if the boiler is or its not cycling as I'm not heating engineer just the owner is there any live stats which will tell me?

Are all the rads heating up properly apart from 1 or 2? - yes I can make all the rads heat up expect this one in the hallway, I can make it to heat up by closing ground floor zone then the hot water will come down to this last radiator in the hallway.

the d.02 reading seems strange, dT of 5C, when the return is actually only lukewarm, these boilers have a internal bypass which comes factory set to 2.5M and is adjustable between 1.7M & 3.5M, doubt if anyone has been messing about with this but I allways think that the 2.5M is quite low, its possible that this bypass is (bypassing) so the actual boiler Hex return temp will be higher than the rads/system return but I don't think the return sensor is located after the bypass. When d.014 is set to auto then the pump speed is controlled between 70% and 100% so 15% (d.015) is actually 74.5% speed or 86% of the max pump head of say 6M which = over 5M (maybe) so difficult to see that some bypassing not taking place but still shouldnt account for the huge difference between the actual and displayed return but it might. - this is a bit complex to me but the boiler had a lot of parts changed including gas exchanger, fan, motherboard, expansion vessel, pump ... not sure what else so maybe one of that part was replaced as well

If the return is say only 30C, (with flowtemp of 75C) then the rad(s) output will only be 56% of their rated output so you would need over 16kw of rads rated output to prevent the boiler from cycling at < 9kw. - so should I change the boiler output from Auto to manual setting ? and if yes what should I put for 15 radiators 4 bed house with loft converted, about 220 sqm

Did any of the engineers test the flow & return sensors?. I don't think they tested it I brought the d40 / d41 difference to their attention but they just looked puzzled and wondering if there is any loop ...

 

[MW9]

I'm trying to balance the radiators again opened all the valves to check which radiators heat first and have those settings on the boiler

D.000 partial load: auto
D.014 pump speed target value: Auto
D.015 the actual speed was showing as 15%
D.019 function mode of 2 speed pump: stage 2 , I tried as well on CH auto and DHW 2

and the boiler reach quickly the temp and cut off for few min , only the closest radiators to the boiler heat up , from 15 radiators only 3 are hot and 4 warm.

the rest are still cold as the boiler keeps cutting off, its 1h and 15 min so far since I started running the system with all valves open to list the order of hitting up.

if I close the 2 radiators next to boiler the hear travel further, still waiting to see how far will it go and if all will heat

I have calculated radiator sizes and roughly I have 20Kw of heat output tricky to calculate as I have 3 towel rails and 3 silver designer radiators so I put them as single panel.

http://simplifydiy.com/plumbing-and-heating/radiators/power

 

[Johntheo5]

It might help to change the output to say 10kw for a start, this wont affect the DHW output.
You seem to have a circulation problem and the boiler just continually cycles but cant keep firng for any useful period.
When the flow temperature reaches SP+5C, in you case 80C then the burner will cut out, the circ pump keeps running, the burner is enabled again at SP-5C, 70C for you but it will not fire until the anticycle time has elapsed, the flowtemperature d.40 should then have fallen to 35C or so to enable the boiler to fire up and not exceed 75C and then run for at least a few minutes before the temperature rises again to 80C. Increasing the pump speed to 4 or 5 may help but not much use if the bypass valve just opens more. If you do increase it note the pump speed. d.15.

When the burner cuts out try and note the time taken for the flowtemperature to fall to 70C and the time (and temperature) taken to refire.

Is there a magnetic filter installed close to the boiler, on the return.

 

[MW9]

It might help to change the output to say 10kw for a start, this wont affect the DHW output.
You seem to have a circulation problem and the boiler just continually cycles but cant keep firng for any useful period.
When the flow temperature reaches SP+5C, in you case 80C then the burner will cut out, the circ pump keeps running, the burner is enabled again at SP-5C, 70C for you but it will not fire until the anticycle time has elapsed, the flowtemperature d.40 should then have fallen to 35C or so to enable the boiler to fire up and not exceed 75C and then run for at least a few minutes before the temperature rises again to 80C. Increasing the pump speed to 4 or 5 may help but not much use if the bypass valve just opens more. If you do increase it note the pump speed. d.15.

When the burner cuts out try and note the time taken for the flowtemperature to fall to 70C and the time (and temperature) taken to refire.

Is there a magnetic filter installed close to the boiler, on the return.

Is there a magnetic filter installed close to the boiler, on the return. - yes there is filter on the return pipe I have empty it few months ago before I have put x400.

 

[Johntheo5]

Maybe chek it again now, especially if it also Iincorporates a particulate filter as well, any more readings?

 

[MW9]

Maybe chek it again now, especially if it also Iincorporates a particulate filter as well, any more readings?

so I have set the
D.000 partial load: auto
D.014 pump speed target value: 100%
D.015 the actual speed is showing as 100%
D.019 function mode of 2 speed pump: stage 2 , I tried as well on CH auto and DHW 2

it seems more stable now in terms of the boiler shutting down and cycling there is still problem with one radiator and te d40 and d41 return temp still showing way too high to what the pipe is feeling to the touch, return pipe under the boiler is lukewarm but inside the boiler the return pipe coming out of the pump is much hotter

I had a call from some valliant engineer and he advised that looks like it might be going via bypass, there might be restriction in the flow pipe, apparently there is some filter in the flow pipe which sometimes can get blocked. I will have an engineer here on Monday

unless someone else got some other ideas for him to check on Monday ?

 

[Johntheo5]

Setting the partial d.00 to 10/12kw may help.

Did you note d.40&d.41 when boiler was cycling?, how long is/was the burner firing for roughly during each cycle?.

Ask the engineer where the return sensor is located, ie, before or after the bypass. get him to check its resistances.

Thats a very good point re flow pipe filter, if installed.

On this particular model showing a filter at minute 3:21.

 

[MW9]

I think the sensors are top left corner, there is a blue clip and red clip so I guess red will be flow and blue return. So the return sensor is on the hot part of the pipe, the return pipe inside the boiler is hot if that make sense, the return pipe below the boiler is lukewarm.

In terms of the d40 / 41 they difference looks like it’s always around 5 degree even when it’s dropping, when the pump stops sometimes I have seen the same temp on the d40 and d41

I have stopped testing for today as the house gets hot so will wait for another chill morning and can do some more readings,

When the pump is in auto the boiler fires for couple min then reach the flow temp limit, and the egg timer kicks in this runs for about 2-3 min flow temp drops to about 50-55 and the burner kicks in and again flow temp reach, egg timer, temp drops and burner kicks in

When I change the pump to 100% the burner fires longer

I have tried partial d.00 and went from 5kw to 24kw raising by 1 to see if it makes some diff ranch but I think it does nothing.

And the d40 and 41 the diffrance is always 5degree does not matter what settings I change to the pump, flow temp, or partial load it’s always 5degree and the return pipe below boiler feels much colder then the d41 shows, unless I open the case and touch the pipe inside the boiler then it feels roughly to what the temp is showing.

 

[DP]

I did drain the the system to flush the x400 and refill with fresh water and added inhibitor

If you check with Sentinel, makers of X400, they will tell you a single drain down will not clear the system of jungle juice. So in effect what you have done is dosed the system with X400 which has done its job, dropped the pressure to zero ( most likely) and dosed the system with inhibitor.

Dropping the pressure to zero does not empty the system, the radiators remain full of water with suspended debris lifted by x400. Woukd have been prudent to leave as is and dose the system.

 

[MW9]

If you check with Sentinel, makers of X400, they will tell you a single drain down will not clear the system of jungle juice. So in effect what you have done is dosed the system with X400 which has done its job, dropped the pressure to zero ( most likely) and dosed the system with inhibitor.

Dropping the pressure to zero does not empty the system, the radiators remain full of water with suspended debris lifted by x400. Woukd have been prudent to leave as is and dose the system

I have used the lowest part of drain, connected hose and started opening the air vents from top floor down, I have used wet / dry vacuum as well to suck remaining debris from this radiator, and I have done it at the other drain as well as I have couple in the house, I have as well opened with the spanner the air vent on that bottom radiator and the other screw from the other end and put the hose in and suck whatever was remaining there with the wet vacuum, it might not be the best drain but its probably better to what it was

this does still not explain the temp on d40 / d41 and potential bypass, I might do another flush on Monday once the guy will be here for the boiler.

 

[Johntheo5]

Now that you have established the position of the return sensor, its more than likely that its reading correctly, strange that the circ pump stops though as it shouldnt during recycle conditions, next time you are doing a few tests check the S status parameters. Also the burner shouldnt cut out at its target temperature of 75C, it should rise to 80C but if the rate of rise is very rapid, easy to miss. I have read of several Vaillant owners where the burner is cutting out at only a few degrees above the target temp but this isnt your root problem.
If you assume the average boiler heat demand is say 8hw, just below its minimum output of 9kw, then assuming the rad returns at 33C and a 75C/70C boiler flow/return will mean that the circ pump flowrate is 22.93LPM of which 20.2LPM is recirculating and only 2.73LPM is circulating through the rads, normally one would expect ~ a dT of say 15C through the rads or a circ flow of 1.0LPM/kw of rad output so the rad circ rate should normally be at least 8LPM for that 8kw output.