Vaillant Ecofit (thread now closed)

[Andrew Edmondson]

This new boiler works fine apart from fluctuating water temperature. The water temp is set to 60C, which is not high enough to sustain a thermostatically controlled shower. Using the instruction, manual I cannot increase the temperature above 60C. I have a Salus wireless thermostat for the radiators and wonder if this is affecting anything.

 

[John D v2.0]

This new boiler works fine apart from fluctuating water temperature. The water temp is set to 60C, which is not high enough to sustain a thermostatically controlled shower. Using the instruction, manual I cannot increase the temperature above 60C. I have a Salus wireless thermostat for the radiators and wonder if this is affecting anything.

60c is the standard cylinder water temperature and more than enough for combi DHW, a thermostatic shower should need 55c at the most, as the necessary output temperature would only be 35-40c. It's wasteful to heat water only to mix it back down again. We have our boiler on 38c and the thermostatic shower works fine.

However the temperature shouldn't be fluctuating. Is it a brand new install? If so get the installer back. If not it may be overheating and cutting out due to blockage or scale, which would also need a registered engineer to deal with.

 

[Madrab]

which is not high enough to sustain a thermostatically controlled shower

Who told you that?

Some thermo mixer do have a min temp at the shower but that would rarely exceed 55deg, any hotter starts to be classed as a scalding risk to the normal consumer. Even then that's just to ensure that it can perform to the manufacturers specifications rather than it won't work. As @John D v2.0 mentions above, min hot water cylinder temp is 60Deg to ensure any bacteria is reduced to a minimum and that usually ends up as outlet temp of >55deg.

An instantaneous hot water heater (combi boiler) should be able to maintain that at the outlet, albeit at a reduced rate/season dependent.

I think you need to measure the hot water temp at a hot tap and see where it's at just now. A brand new boiler would rarely have fluctuating temps like that unless it hasn't been installed correctly either that or the issue is at the shower cartridge.

What make/model is the shower and what model of Ecofit?

 

[Andrew Edmondson]

Thanks very much for the informative replies.

I've measured the tap temperature, which rises to a stable 50C but this is only when the CH is on.

When the CH is off, the tap temperature varies in a cycle from lukewarm to hot.

I had the same problem with the boiler this one replaced. Every year I had to replace the thermistors.

The pipes and radiators were cleaned over a week using Fernox F3 then treated with Fernox F1. I also fitted a magnetic filter. So I don't think this can be a sludge problem.

It is a brand new Ecofit 830 boiler, so I assume it is a control problem.

 

[Madrab]

Yeah ..... If the boiler is cycling on and off then there's an issue somewhere. I'd be getting your installer back out as something isn't right. I don't there's an adjustable parameter on the Ecofit Pure units, it's factory set.

 

[muggles]

I had the same problem with the boiler this one replaced.

I think this is the critical statement here. If both your old and new boiler are showing the same symptoms, it's highly unlikely to be a boiler problem. It's more likely to be a faulty mixer tap or shower causing cold water to be blended with the hot before it reaches the shower.

Is every outlet affected, or just some of them?

Putting check valves on the supplies to each appliance would be a good start

 

[ianmcd]

sounds like you have a faulty shower or mixer somewhere

 

[Andrew Edmondson]

I tested a hot tap (without thermostatic valve) and found that the temperature gradually reaches 50C over 15 minutes, starting at 39.5C. No cycling this time.
50C is not hot enough to fill a bowl though.

The thermostatic shower initially dipped in temperature then stabilised. I'll check it a few more times whilst having a shower.

 

[ianmcd]

isolate the cold water inlet below the boiler, open a hot tap until it stops then close, then turn your shower to hot max and open the valve , if you get water coming out the cartridge is mixing

 

[ianmcd]

50C is not hot enough to fill a bowl though.

what are you washing ? 50c is way too hot for your hands

 

[Madrab]

50C is not hot enough to fill a bowl though

50 Degc is the recommend output temp at the tap, any hotter would be classed as a scalding risk.

Your shower may also need calibrated and adjusted.

 

[Andrew Edmondson]

Thanks Ian
Cylinder minimum temp is 60C. That's what we are used to.
I'll try what you suggest.

 

[ianmcd]

Thanks Ian
Cylinder minimum temp is 60C. That's what we are used to.
I'll try what you suggest.

The cylinder is set at that due to Legionella regulations, what Vaillant eco fit do you have there are a few , I thought you had a combi but now you are saying you have a cylinder

 

[ScottishGasMan]

You will rarely get 60 out of any combi unless your running a very low flow of water through the taps.

Setting a combi at 60, doesnt make the water come out the tap at 60, it limits the maximum temperature to 60, the actual temperature depends on how warm the cold supply is and how fast you run the water, most of the vaillants are sized and restricted to give roughtly a 42 degree rise in the cold water temp to hot water, so for 60 degrees you would need about 18 degrees in your cold main coming in, which is probably about 16 more than you will actually have at this time of year.

Get the thermometer out, run the hot water, (give the boiler a couple of minutes to have hot water running steady at tap) and watch the temperature, if its fluctuating up and down significantly then yes, there may be a fault in the boiler (or just as likley in your plumbing somewhere) but if its giving a steady temp, which is in the region of 35-40 degrees above that of your cold water, then its probably working exactly as its specified to do

 

[ianmcd]

You will rarely get 60 out of any combi unless your running a very low flow of water through the taps.

Setting a combi at 60, doesnt make the water come out the tap at 60, it limits the maximum temperature to 60, the actual temperature depends on how warm the cold supply is and how fast you run the water, most of the vaillants are sized and restricted to give roughtly a 42 degree rise in the cold water temp to hot water, so for 60 degrees you would need about 18 degrees in your cold main coming in, which is probably about 16 more than you will actually have at this time of year.

Get the thermometer out, run the hot water, (give the boiler a couple of minutes to have hot water running steady at tap) and watch the temperature, if its fluctuating up and down significantly then yes, there may be a fault in the boiler (or just as likley in your plumbing somewhere) but if its giving a steady temp, which is in the region of 35-40 degrees above that of your cold water, then its probably working exactly as its specified to do

Totally correct but the OP is now saying he has a Cylinder