New Vaillant Ecotec Plus 832 DHW flow rate much lower than old 24kw combi it replaced

[smallfry]

Our 17+ year old Worcester Bosch GREENSTAR 24i Junior recently broke (again) so it got replaced with a Vallant Ecotec Plus 832 (facelift version with screen). This was upsized from the previous 24kw because of extensions in our home since the WB was fitted - 6 more rads and additional shower room etc.

Since the Ecotec Plus 832 was fitted we've noticed a dramatic reduction of DHW flow rate - 30-50% lower than the old 24kw combi.

The gas engineer who installed the boiler has been back to fault find but still no closer to a solution.

CW mains supply was measured on garden tap and shows pressure is 2 bar with ~18l/min flow (using flow measure cup). CW flow from basin nearest the boiler (1st floor) is about the same.

With a single shower running fully hot we're getting ~6.5 l/min (as measured by the impeller in the boiler - installer had the boiler in service mode). With a two addtional hot taps on the flow maxed out at 7.8 l/min.

This is well below the stated spec for the boiler which is 13 l/min (35c delta).

Has anyone seen this before?

Any suggestions how to resolve?

Vaillant engineer coming on thursday, but given no error code on boiler our expectations of help are low...

 

[Johntheo5]

You're getting 6.5/7.8LPM as measured by D.036, Domestic hot water circuit flow rate?, have you measured it at a tap?.
that only requires a boiler output of 15.87/19.05kw @ 35C dT.
Are all/any isolating valves on the mains to the boiler opened & any restrictor removed?.

 

[CountryFan]

With a single shower running fully hot we're getting ~6.5 l/min (as measured by the impeller in the boiler - installer had the boiler in service mode). With a two addtional hot taps on the flow maxed out at 7.8 l/min.

What’s it like with just one hot outlet running?

Any suggestions how to resolve?

Check individual hot taps for flow rate

Vaillant engineer coming on thursday, but given no error code on boiler our expectations of help are low...

The engineer might help as in point you in the right direction but if all is well with the boiler supplying taps, then it seems a pointless visit

 

[smallfry]

Thanks for reply.
Correct - 6.5l/m w shower on and 7.8l/m with shower + 2 hot taps measured on boiler display.
(I assume D.036 is the vaillant code for that measurement?)
We haver measured at tap using measure cup and was ~4-5l/m.
Mains stopcock and valve on the boiler CW inlet are both fully open.
Only difference between original and new CW water supply to the boiler is the magnetic descaler that comes as part of the Vaillant install kit and which is apparantly necessary for the 10yr warranty. Our installer told us that does not affect the flow (magnetic?) but even if it does, its a choice of that or no warranty...

 

[smallfry]

What’s it like with just one hot outlet running?

Check individual hot taps for flow rate

The engineer might help as in point you in the right direction but if all is well with the boiler supplying taps, then it seems a pointless visit

With just one tap it was 4.79l/m (kitchen tap)
Cant measure anything else as I dont own a measure cup (was installer) not access to the installer menu on boiler.
Thanks for the reply

 

[Johntheo5]

With just one tap it was 4.79l/m (kitchen tap)
Cant measure anything else as I dont own a measure cup (was installer) not access to the installer menu on boiler.
Thanks for the reply

You don't need a measuring cup, just hold a container under the tap or whatever for exactly 15 secs, measure this with a 1 litre milk bottle or whatever and X 4 to give the flowrate in LPM, take a few more measurements.

Thanks for reply.
Correct - 6.5l/m w shower on and 7.8l/m with shower + 2 hot taps measured on boiler display.
(I assume D.036 is the vaillant code for that measurement?)
We haver measured at tap using measure cup and was ~4-5l/m.
Mains stopcock and valve on the boiler CW inlet are both fully open.
Only difference between original and new CW water supply to the boiler is the magnetic descaler that comes as part of the Vaillant install kit and which is apparantly necessary for the 10yr warranty. Our installer told us that does not affect the flow (magnetic?) but even if it does, its a choice of that or no warranty...

The magnetic filter is on the primary circuit so no effect on the DHW flowrate.,

 

[smallfry]

You don't need a measuring cup, just hold a container under the tap or whatever for exactly 15 secs, measure this with a 1 litre milk bottle or whatever and X 4 to give the flowrate in LPM, take a few more measurements.



The magnetic filter is on the primary circuit so no effect on the DHW flowrate.,

Good point on measuring the traditional way Will post back...
Re filters the CH circuit has a magnaclean (pre-existing) + the vaillant mandated magnetic filter (obs not related to the DWH)
The CW inlet to the boiler has a "Cal Mag" inline scale inhibitor between the isolation valve and boiler.

 

[smallfry]

Good point on measuring the traditional way Will post back...
Re filters the CH circuit has a magnaclean (pre-existing) + the vaillant mandated magnetic filter (obs not related to the DWH)
The CW inlet to the boiler has a "Cal Mag" inline scale inhibitor between the isolation valve and boiler.

Measured both kitchen and utility taps (one floor below boiler). Both are about 4.8l/min tested individually

 

[Johntheo5]

Measured both kitchen and utility taps (one floor below boiler). Both are about 4.8l/min tested individually

So, there is no "extra" filters etc on the mains supply to this boiler (for DHW) vs the other boiler??.

 

[RandomGrinch]

So, there is no "extra" filters etc on the mains supply to this boiler (for DHW) vs the other boiler??.

Sorry I didn't know if you missed this...

The CW inlet to the boiler has a "Cal Mag" inline scale inhibitor

Only difference between original and new CW water supply to the boiler is the magnetic descaler

Although most of the CalMag filters I can find have a maximum flow rate of 1l/s...

As it seems to be the only difference in the setup, it may not take much effort to bypass it, just to rule it out as the issue?

 

[smallfry]

So, there is no "extra" filters etc on the mains supply to this boiler (for DHW) vs the other boiler??.

Its connected:

Mains ---> Main stop cock ---> boiler isolation valve ---> Cal mag scale inhibitor ---> boiler

Sorry I didn't know if you missed this...



Although most of the CalMag filters I can find have a maximum flow rate of 1l/s...

View attachment 366346

As it seems to be the only difference in the setup, it may not take much effort to bypass it, just to rule it out as the issue?

Yes thats what I saw also - 1.08l/sec = ~65l/min so that is much higher than the supply.

 

[Johntheo5]

Yes, just remove it temporarily even though the dP through it should only be ~ 5% of the dP at 65LPM, (15/65)squared?

 

[Johntheo5]

Do these type of filters work?, I thought they were the equivalent of the medicine doctor's snake oil.

 

[smallfry]

Thanks - if no luck with Vaillant engineer then will try removing to see if it makes a difference.
Not sure if these are snake oil, but afaik its part of the compliance kit for the 10 yr warranty

 

[ScottishGasMan]

Just be aware the 832 flow rate is 10.4 l/min not the 13 l/min you initially stated. However obviously you are falling below even that.

Its possible something simple has happened like dirt/dust has got into the pipes during the boiler swap and is restricting the boiler inlet filter and a simple clean of that by the engineer will resolve.