Valliant Boiler ecotech 832- Heating Partial Load

[tommys1985]

Hi all - looking to optimise my boiler heating to see how to make it more efficient.

My setup is:


Combi boiler, someone configured by engineer to provide heating and also warm up my hot water tank.
The kitchen tap is connected to DHW from the boiler to ensure diverter doesn't jam up? This was the recommendation from Valliant.
4 bed house - 11 radiators in total.


Currently it is running on full 24KWH and 60c. I have noticed the following:

1. Return temp is always 4c difference between flow and return.


I have reduced D014 pump speed to 53% and it has not done anything. What else can I do to increase efficient of the boiler?

 

[Harry Bloomfield]

What else can I do to increase efficient of the boiler?

Do what I did, replace your present controls, with a Vaillant control system.

 

[tommys1985]

Do what I did, replace your present controls, with a Vaillant control system.

can I ask what you went for and what changes you have noticed?

 

[Harry Bloomfield]

can I ask what you went for and what changes you have noticed?

The full VRC470F system, including outdoor sensor. It predicts, precisely how much heat it needs to generate, to meet your setting, you just set and forget - it does the rest, tells the boiler how much to modulate. Room temperatures, just remain stable, with no more of the creaking of pipes, as the heating cuts on and off. It also saves a bit of fuel too.

 

[Johntheo5]

Hi all - looking to optimise my boiler heating to see how to make it more efficient.

My setup is:


Combi boiler, someone configured by engineer to provide heating and also warm up my hot water tank.
The kitchen tap is connected to DHW from the boiler to ensure diverter doesn't jam up? This was the recommendation from Valliant.
4 bed house - 11 radiators in total.


Currently it is running on full 24KWH and 60c. I have noticed the following:

1. Return temp is always 4c difference between flow and return.


I have reduced D014 pump speed to 53% and it has not done anything. What else can I do to increase efficient of the boiler?

Hi all - looking to optimise my boiler heating to see how to make it more efficient.

My setup is:


Combi boiler, someone configured by engineer to provide heating and also warm up my hot water tank.
The kitchen tap is connected to DHW from the boiler to ensure diverter doesn't jam up? This was the recommendation from Valliant.
4 bed house - 11 radiators in total.


Currently it is running on full 24KWH and 60c. I have noticed the following:

1. Return temp is always 4c difference between flow and return.


I have reduced D014 pump speed to 53% and it has not done anything. What else can I do to increase efficient of the boiler?
[/QUOTE]

Its very surprising that the dT is only 4C even if all the rad lockshield valves are full open, these boilers have a adjustable bypass screw, normally in mid position and even with a pump speed of 53% might still be bypassing, can you measure the boiler return before it enters the boiler?, I have seen numerous posts where someone has balanced all the rads to give say 15C dT (return measured before the boiler) only to find that the by pass was reduing this to 6 or 7C but yours is exceptionally low IMO, maybe check out this screw, if in its default position then ~ 7 turns clockwise should put in its minimum by pass position but Vaillant then recommend that you increase the pump speed to 100%.
There is also a "d" parameter where you can change to return temperature control but I rarely see anyone using it, might be worth a try?, pump would probably need to be in Auto then.

When you requested 53% pump speed did the speed actually fall to 53%.

 

[tommys1985]

Hi all - looking to optimise my boiler heating to see how to make it more efficient.

My setup is:


Combi boiler, someone configured by engineer to provide heating and also warm up my hot water tank.
The kitchen tap is connected to DHW from the boiler to ensure diverter doesn't jam up? This was the recommendation from Valliant.
4 bed house - 11 radiators in total.


Currently it is running on full 24KWH and 60c. I have noticed the following:

1. Return temp is always 4c difference between flow and return.


I have reduced D014 pump speed to 53% and it has not done anything. What else can I do to increase efficient of the boiler?

Its very surprising that the dT is only 4C even if all the rad lockshield valves are full open, these boilers have a adjustable bypass screw, normally in mid position and even with a pump speed of 53% might still be bypassing, can you measure the boiler return before it enters the boiler?, I have seen numerous posts where someone has balanced all the rads to give say 15C dT (return measured before the boiler) only to find that the by pass was reduing this to 6 or 7C but yours is exceptionally low IMO, maybe check out this screw, if in its default position then ~ 7 turns clockwise should put in its minimum by pass position but Vaillant then recommend that you increase the pump speed to 100%.
There is also a "d" parameter where you can change to return temperature control but I rarely see anyone using it, might be worth a try?, pump would probably need to be in Auto then.

When you requested 53% pump speed did the speed actually fall to 53%.
[/QUOTE]


I don't want to mess with the bypass valve as it means opening the boiler...anything else I can try? the pump does show 53% but if i leave on auto then I have seen 15% also?

 

[Johntheo5]

Can't see it circulating practically anything, at 15% speed. Pump head is proportional to speed squared, this pump will have a head of between 6M and 7M at full speed, say 6.5M, so head at 15% speed will be 0.15 squared X 6.5, 0.15M, it will circulate nothing at that speed, also flow is directly proportional to speed, so IF the speed fell to 15% then the flow/return dT, for the same boiler output should rise to 4C/0.15, 26.7C, theoretically possibly.

The 53% makes some sense, head will be, 0.53squared X 6.5, 1.83, dT shold be 4C/0.53. 7.55C.

You said" Currently it is running on full 24KWH and 60c. I have noticed the following:
1. Return temp is always 4c difference between flow and return."

Do you mean that d.00, the output setting is set to 24kw?

What you could do, which will give some useful info IMO is, With the 11 rads running and up to temperature, gradually reduce d.00 (it can be reduced in 1kw steps) until the flowtemp of 60C just begins to fall off, note the kw setting which will then be the actual boiler output and note flow/return temps, d.40/d.41, can then do a few calcs which might show up something, return d.00 to its original setting when data noted.

 

[tommys1985]

Do you mean that d.00, the output setting is set to 24kw?

Yes it is set to 24KWH.

 

[Johntheo5]

Can you do the test as above, that will tell a lot, maybe reduce it to 15kw for the first change, then if d.40 remains steady reduce it in 1kw steps until the flowtemp d.40m starts falling, then note the flow/return temps and the pump speed after say another 2 minutes.

 

[Delta925]

Your model may be different but I thought for Vaillant D00 was the maximum output in heating mode setting. Initially from cold this will be delivered but once the outlet temperature reaches that set the boiler then automatically backs off. For my boiler this D00 is set to 12kW.
Of all the Dxxx codes / settings there is not one that shows the actual output or even the theortical demanded heat output though. The only indication is from the normal display where the flame symbol with a 5 - step bargraph at the side. At 12kW this is 2 bars then it drops to one.

The best dT I can achieve once stabilised is around 10C. This with the boiler in dT mode rather than dP, a set dT of 15C and an output temperature of 60C. From the manual the lowest heat output of my boiler is stated as 3.7kW. Purely going by the kW usage from my meter monitor I do not think it is going down to this but only around 6kW. If it would drop to 3.7kW then dT would increase and hence efficiency from condensing.

I have pump speed control set automatically with the Dxx codes just readings of actual speed, flow and %. I would need to look but I don't think I can set it manually. Even if I could I don't think I would want to as against faster when cold then backing off so combined with heat input reducing ideally the set dT is achieved.

 

[Johntheo5]

Is it something like the attached one that a friend of mine installed a year ago where you set the dT between I think 10C & 20C but he couldn't even though the pump speed was well above its minimum turn down of 50% in Auto, A common problem with all Vallients and probabvly all boilers with internal bypasses (system&combi boilers only I think) is that you can spend hours nicely balancing your rads to say give a dT of 15C only to find that the actual boiler dT is ~7C due to this bypass, it is adjustable, but if you turn it to minimum then Vaillant say you must run the pump at 100%.

 

[Delta925]

It is a Vaillant Ecotech plus 832, the latest version without the door over the screen.

From the manual it should only be run in dP mode with radiators. dT should only be be used for full or partial underfloor heating.
I did set dP down to the minimum 100mbar but then slow to heat initially and once stable from the boiler readings dT under 10 degC.
On trying dT I can get a faster warm up and better dT once stable so don't see a massive issue particularly with the fanned convector - see below.
I'd need to monitor again but think the pump speed goes down to around 20%.

The installation is 50 years old of course designed for a vented system. If modern microbore then I presume a higher pressure drop and what Vaillant design for.
The boiler is in the garage. The feed pipes from the boiler to where originally the Y-plan valve and hot water cylinder were are 22mm. From there two 15mm runs to upstairs radiators, 22mm going downstairs then ( I presume as in concrete floor ) all 15mm distribution downstairs.

All the basic radiators have a new TRV and lockshield set. None of the lockshield are very far open but if closed more to give a dT more than 10C then minimal flow and hence output.
None of the potential installers suggested replacing radiators but in hindsight maybe it should have been done.
In the lounge is a Myson 14-10 fanned radiator which is effectively one bypass. The control board is faulty. It simply has a 50C thermal switch on the feed pipe which sets the fan to the medium speed. The outlet / return temperature is around 40C i.e. dT 20C. I have tried partly closing the return isolation valve to simulate a lockshield valve but end up just cutting the heat output with no significant effect on the overall boiler return temperature.

Having said all this and presuming the boiler efficiency not much lower for a low heat output so ~6kW gas input is delivering the minimum 3.7kW output if the boiler would drop to 3.7kW then dT would increase. The ideal 20C clearly is not achievable but I think 15C would be.

 

[Delta925]

....
Of all the Dxxx codes / settings there is not one that shows the actual output or even the theoretical demanded heat output though .....

No doubt known / obvious to those familiar with modern boilers but I have just read that modulation is the control of the heat input.

Looking at the manual I can not see a Dxxx code for modulation but I thought I had seen it and recall with 60C output temperature achieved it was 18%. If I am right then 18% of 32kW is 5.76kW. This fits with my estimated 6kW from gas use. For 3.7kW output modulation ( theoretically ) would be 12%.

 

[tommys1985]

Your model may be different but I thought for Vaillant D00 was the maximum output in heating mode setting. Initially from cold this will be delivered but once the outlet temperature reaches that set the boiler then automatically backs off. For my boiler this D00 is set to 12kW.
Of all the Dxxx codes / settings there is not one that shows the actual output or even the theortical demanded heat output though. The only indication is from the normal display where the flame symbol with a 5 - step bargraph at the side. At 12kW this is 2 bars then it drops to one.

The best dT I can achieve once stabilised is around 10C. This with the boiler in dT mode rather than dP, a set dT of 15C and an output temperature of 60C. From the manual the lowest heat output of my boiler is stated as 3.7kW. Purely going by the kW usage from my meter monitor I do not think it is going down to this but only around 6kW. If it would drop to 3.7kW then dT would increase and hence efficiency from condensing.

I have pump speed control set automatically with the Dxx codes just readings of actual speed, flow and %. I would need to look but I don't think I can set it manually. Even if I could I don't think I would want to as against faster when cold then backing off so combined with heat input reducing ideally the set dT is achieved.

sorry for my ignorance. how do i check if it set to DP or DT mode?

 

[Delta925]

sorry for my ignorance. how do i check if it set to DP or DT mode?

dP or dT mode then the settings are Dxxx codes.
The explanation of the modes is in the manual, for mine section 10.3.5 then 10.3.6 - 10.3.8 explain the pressure and the pump.

For mine right at the end which I presume is intentional so you access by scrolling back from D000 not going right through the list.
First check / set the mode then the relevant active codes follow.
D170 is the mode. Out of the box and as left by the installer set to 2 for dP. Change to 3 for dP.
Then D172 is dT, D173 is minimum dP and D174 is maximum dP.
When in dP D171 sets target dP - range 100 - 400 mbar.


With dT set dP is in the background with a minimum setting of 100mbar. I think for my system once stabilised achieving dP of 100mbar is what is in control.

Once both I have time and the weather turns colder I might try fine adjustment of the lockshield valves to see if I can increase the pipe / radiator loop pressure drop without a significant loss of heat output. Another experiment will be turn all the TRV's to minimum so radiators off and just the Myson convector in circuit then see what the flow rate, pump speed and return temperature is plus modulation when I find where I saw it - unless dreaming!

I don't want to mess with the bypass valve as it means opening the boiler...anything else I can try? the pump does show 53% but if i leave on auto then I have seen 15% also?

Likewise. As I interpret my manual 10.3.6 the change is where with dP at 400mbar too little flow.
Maybe wrong but I'm thinking my issue is too little pressure / flow too fast so radiators are not taking enough heat out the water hence dT too low.