a good hot bath

[AJSmif]

Recently had my CH system updated to a vaillant ecotec 428 (open vent).
Previous system was basic and did not have cylinder thermostat not 3 prt valve etc, wheras new noe does.

Having a bit of trouble getting hot water hot enough (not using CH part at the mo)...

Now with old system we got a cylinder full of hot water ... enough to have a deep, really hot bath...(sorry I don't have any measurement of what "really hot" is? -- say the sort of bath that needs 1/3 cold water to bring it down to the temp you could just get in).

with new system (same cylinder) ... it never seems to gets as hot... bath is ok but not really hot...

I have cylider thermostat (danfoss ATC) set to 65c ... but I notice boiler max for HW is only 65c as well? So I could up the cylinder stat - but beyond 65c seems to be above normal recommendadtions? And would it do any good if boiler will only go to 65c?...

What should I be setting boiler HW therostat to and what the cylinder thermostat to get a cylinder full of really hot water once a day?

thanks for any help
Andy

 

[Armo74]

Cylinder stat needs to be set at 60-65 degrees and also should be set at the correct height which is a 1/3 of the way up from the bottom of your cylinder obviously boiler should be set at a higher temperature than you have it.

 

[ALEC1]

unless you have ebus controls one of the two knobs on the vaillant won't do anything..

 

[AJSmif]

unless you have ebus controls one of the two knobs on the vaillant won't do anything..

Ah - how can I tell if I have "ebus controls"?

(as far as I know... system is vaillant 428 boiler + 3 port valve, cylinder stat, room stat & grundfoss pump, plus Danfoss FP715 programmer)

thanks
Andy

 

[AJSmif]

Cylinder stat needs to be set at 60-65 degrees and also should be set at the correct height which is a 1/3 of the way up from the bottom of your cylinder obviously boiler should be set at a higher temperature than you have it.

thanks
Cylinder is set about 65c ...
boiler has 2 thermostat dials ... one of HW, one for CH... the max that the boiler HW dial can be set is 65c (seems a bit low to me?).

thanks

 

[Phill Peck]

unless you have ebus controls one of the two knobs on the vaillant won't do anything..

Ah - how can I tell if I have "ebus controls"?

(as far as I know... system is vaillant 428 boiler + 3 port valve, cylinder stat, room stat & grundfoss pump, plus Danfoss FP715 programmer)

thanks
Andy

You don't have ebus controls

The hw knob on boiler won't effect anything

What is the ch knob set to?
How long do you have hw on for on programmer?
What is programmer set to? (on off allday auto?)

Your installer should have explained this stuff to you

 

[AJSmif]

unless you have ebus controls one of the two knobs on the vaillant won't do anything..

Ah - how can I tell if I have "ebus controls"?

(as far as I know... system is vaillant 428 boiler + 3 port valve, cylinder stat, room stat & grundfoss pump, plus Danfoss FP715 programmer)

thanks
Andy

You don't have ebus controls

The hw knob on boiler won't effect anything

What is the ch knob set to?
How long do you have hw on for on programmer?
What is programmer set to? (on off allday auto?)

Your installer should have explained this stuff to you

Aahhh ...
so even though when I turn the HW knob the boiler panel shows temperatures up to 65c it is doing nothing ?!?

The CH (the one with the radiator symbol) is set about halfway (53c)... as it is summer(ish) the CH is off on the programmer with the HW set to auto (couple of hours in morning, about 5 hours evening)?

If the Boiler HW control does nothing what is controlling the water temp?
(other than the cylinder thermostat?)...


The installer was pretty good - but I wasn't around when he completed ... & my wife didn't catch all he said ... maybe I should be calling him back?

I thought I understood how it works but didn't realise the HW dial on the boiler does nothing (poor design if the panel show temp changes when I twist the hw dial ... would make more sense if the dial was blanked out).

This is an eye opener - Really grateful for your advice.
Andy

 

[Phill Peck]

Right the ch knob controls the temperature of the water in the radiators an hw cylinder coil
So if you have it set to 53 you will be getting somewhere in the high 40's water temp in cylinder

Turn that up to about 65 and problem solved

If you have zone valves and a room thermostat there is no need to turn this knob down in the summer

Also my advise would be to run your hot water on allday this way it will maintain the temperature allday and should be more efficient than trying to re heat the water in the evening

 

[Phill Peck]

You used to be able to buy blanks to cover them not sure if u still can

 

[AJSmif]

Right the ch knob controls the temperature of the water in the radiators an hw cylinder coil
So if you have it set to 53 you will be getting somewhere in the high 40's water temp in cylinder

Turn that up to about 65 and problem solved

If you have zone valves and a room thermostat there is no need to turn this knob down in the summer

Also my advise would be to run your hot water on allday this way it will maintain the temperature allday and should be more efficient than trying to re heat the water in the evening

Suddenly it all makes sense... now I know that the dial I was adjusting does nothing

So just to clarify ... there is only one working boiler stat with my setup... and that should be about 65c... and the cylinder stat should be a few degrees lower (say 60c)... and so long as it is on long enough we should be back to a hot bath at night.

Thanks again for you help.
Andy

 

[Phill Peck]

Right the ch knob controls the temperature of the water in the radiators an hw cylinder coil
So if you have it set to 53 you will be getting somewhere in the high 40's water temp in cylinder

Turn that up to about 65 and problem solved

If you have zone valves and a room thermostat there is no need to turn this knob down in the summer

Also my advise would be to run your hot water on allday this way it will maintain the temperature allday and should be more efficient than trying to re heat the water in the evening

Suddenly it all makes sense... now I know that the dial I was adjusting does nothing

So just to clarify ... there is only one working boiler stat with my setup... and that should be about 65c... and the cylinder stat should be a few degrees lower (say 60c)... and so long as it is on long enough we should be back to a hot bath at night.

Thanks again for you help.
Andy

Pretty much yes

I normally set cylinder stats at 55 but it sounds like u want very hot water.

65 is just my suggestion and what I leave my installs on.

You will loose some heat from the boiler to cylinder so yes it needs to be few degrees high than cylinder stat

 

[AJSmif]

Right the ch knob controls the temperature of the water in the radiators an hw cylinder coil ...
Turn that up to about 65 and problem solved ...

...
Suddenly it all makes sense... now I know that the dial I was adjusting does nothing

So just to clarify ... there is only one working boiler stat with my setup... and that should be about 65c... and the cylinder stat should be a few degrees lower (say 60c)... and so long as it is on long enough we should be back to a hot bath at night.

Thanks again for you help.
Andy

....

Just to reopen this thread... as I’m still having a bit of trouble with the actual “out of the tap” HW temperature.

Installation is still the same (new vaillant 428 boiler + 3 port valve, cylinder stat, room stat & grundfoss pump, plus Danfoss FP715 programmer - Read more: //www.diynot.com/forums/plumbing/a-good-hot-bath.336315).

I bought a cheap digital thermometer to help measure cylinder & tap temp …

Seems no matter what I set the boiler stat, or the cylinder stat – I cannot get the water really hot… (digital thermometer reports 53-54c)

With the stat on the boiler is set to 65... I’ve set the cylinder one day to 60c,next to 65c, next to 70c… each time I get the same tank/water temp… the digital thermometer reads about 54c on the tank (cylinder stat height) about 0.5c hotter at the top of the tank, and about 0.5-1.0c colder out of the tap.

Tried with the stat on the boiler set to 70c … and the cylinder stat at 65c again using… get the same (approx 54c) temps at the tank / tap.

I appreciate the digital thermometer may not be fully accurate – but it is consistent…

Some extra background info
• The programmer has Hw on auto (5:30 - 10:30pm)... the CH off (not for much longer according to s.w.m.b.o.).
• While heating up … I see the boiler burner seems to go on full for about a minute – until the flow reaches the boiler stat setting … then cuts out until the flow drops below 50c then repeats again.
• There seem to be significant periods when the boiler is in status S.7 (pump overrun) and s.8(anti cycling) – not sure what this is. And the pump also goes on and off during this time
• It takes the cylinder about and hour or so to reach its stable temp. Then if noone uses water the system shuts down (s.30 no burner, no pump). At this stage if you turn the cylinder stat up, the system fire up again – but the water doesn’t seem to get any hotter (still about 54c).

Very Strange? Any ideas? Faulty cylinder stat? something not wired right?
Thanks Andy

 

[JohnD]

what colour is the insulation on the cylinder?

When you have CH off and HW on, does any heat go to the rads?

 

[AJSmif]

what colour is the insulation on the cylinder?

When you have CH off and HW on, does any heat go to the rads?

Actually the cylinder is the old fashion copper one... with a new red insulation jacket on it. (when HW is off ... it seems to cool down by very approximately 1c per hour)

Radiators stay cold when only HW on.

thanks