HOT, very hot, too hot, hot water, stored, cylinders,

[Ted808]

Hey guys
I've had a two jobs where cust is complaining of hot water being too hot. One is an old UNVH cylinder and the other is a very, very old hot water-yellow jacket and cold storage tank set-up.
Now I'm wondering this is - why has the water over time apparently got hotter?
Bear in mind, in both cases the cylinder stat set to 60*C ( as accurate as these can be over time...that's another story ) but the water is coming out at the furtherest tap about 57* - so that's a little too hot. I would like it nearer 42*-44*. Nothing has changed on the system/s but I realise weather is warmer- so maybe shorten heating time?
I'm not going to put in blender valves in.
Someone suggested, limescale build up on the cylinder is holding on to heat so that even when timer/heat is off it continues to generate heat?
What's your thoughts on this?

 

[Chalked]

Cylinder stats go out over time.
Just turn it down to desired temp and ignore the number

 

[Stigster]

The thing is it should be hot, too hot to put hands under. A blending valve is the proper way to go about it rather than turning the cylinder temp down if it's at 60 - 65C. Obviously if it has crept up to 70 or more then turning it down to around 65 is the right thing to do. It's certainly worth getting a temperature reading right at the cylinder to know where it's really at.

 

[townfanjon]

Whatever the HW temp is leaving the cylinder , it will only be a few degrees cooler when it gets to the taps . Blender is the only way .
Depending on the cylinder capacity and therefore height it also has a bearing on the temp , cylinder stat 1/3 up from bottom , tall cylinder 210 / 250 etc stat set at 60 it will probably leave the cylinder at 65 ish .

 

[leesparkykent]

Is the vented cylinder on a Y plan?

 

[Ted808]

Chalked would you say that having 42* at the tap will still get the cy

The thing is it should be hot, too hot to put hands under. A blending valve is the proper way to go about it rather than turning the cylinder temp down if it's at 60 - 65C. Obviously if it has crept up to 70 or more then turning it down to around 65 is the right thing to do. It's certainly worth getting a temperature reading right at the cylinder to know where it's really at.[/QUOTE
This sound feasible but I've not seen many blendervalves in old domestic installs. I've seen a few on high end new installs with more than occupant- rented rooms with central boiler type system. Also, I've done some research and 42* is the desired temperature at hot water outlets to prevent scalding. In an old house, folks just want a reasonable solution. It's a bit tricky to set the temperature, as you can't measure the cylinder temp accurately. It also fluctuates and it would involve more than one visit which feels like a - taking the mick ... so I'm left scratching my chin.......

 

[Ted808]

Is the vented cylinder on a Y plan?

Does it matter?

 

[Ted808]

Whatever the HW temp is leaving the cylinder , it will only be a few degrees cooler when it gets to the taps . Blender is the only way .
Depending on the cylinder capacity and therefore height it also has a bearing on the temp , cylinder stat 1/3 up from bottom , tall cylinder 210 / 250 etc stat set at 60 it will probably leave the cylinder at 65 ish .

How do you come to this conclusion? I mean is there some printed info on this. Just trying to understand and learn as much as possible- cheers

 

[townfanjon]

Its just general unvented knowledge pal . When HW is heated it “ stratifies “ I suppose its a bit like in imaginary layers . So with the stat being a lot lower than the top it stands to reason the top is a lot hotter and also because the cylinder is under pressure it gets to the taps in seconds hence the HW doesnt loose many degrees . TMV’s are the only way forward .

 

[leesparkykent]

Does it matter?

Yes.

 

[Ted808]

Yes.

Why? Please explain a little more.

 

[Ted808]

I have two different situation's - one it's a vented cylinder on a Y plan and the other is an Unvented on S plan. In both cases the water has seemed to increase in temp over time- I am trying to understand why this is- besides seasonal changes and general design, could there be a proper reason or are both customers imagining it?

 

[Last Plumber]

I have two different situation's - one it's a vented cylinder on a Y plan and the other is an Unvented on S plan. In both cases the water has seemed to increase in temp over time- I am trying to understand why this is- besides seasonal changes and general design, could there be a proper reason or are both customers imagining it?

I might be missing what you want to know here!
If you've set the Cyl Stat to 60 C (like you're supposed to) and it is 57 C at the draw off point, what's wrong?
If it is just that the customer is burning themselves, as Townfanjon said, you need to install a TMV. The cylinder is set at that for a reason isn't it?

 

[Ted808]

The point is the customers feel that the water temperature has increased over time. DOES this seem probable?

 

[Ted808]

What's the difference if it's Y plan or not? Unvented or vented.
I know the cylinder stat has to be set 60*.
I'm just saying , blender valves are not generally routinely installed on domestic systems, not that I've seen.

 

[Stigster]

What's the difference if it's Y plan or not? Unvented or vented.
I know the cylinder stat has to be set 60*.
I'm just saying , blender valves are not generally routinely installed on domestic systems, not that I've seen.

They aren't installed by routine but there are regulations regarding water temperature at outlets and "vulnerable persons" where you would install blending valves. Also if a customer is complaining the water at the outlet is too hot, the only answer is a mixer tap for those happy to blend their own temperature and/or blending valves for those that never want water to exceed a set temperature.