Hot water to hot on gravity fed

[shyguy2005]

Hi guys wonder if someone could help.

Hot water on a gravity fed system (y plan) is far too hot. Tried swapping cylinder stat but is the same. With hot water on the boiler fires up even when cylinder stat is set at 50c. If I turn the stat down lower the pump and boiler go off.

Customer has hot water on constant all day.

Thinking maybe 3 port valve?

 

[AMGasServices]

What boiler do they have ? (I’d try turning the temperature down on the boiler).

You state once you turn the cylinder stat down the boiler and pump go off. That indicates that the 3 port valve appears to be working fine.

Would it be better to set a timer for the How water rather than constant?

 

[shyguy2005]

What boiler do they have ? (I’d try turning the temperature down on the boiler).

You state once you turn the cylinder stat down the boiler and pump go off. That indicates that the 3 port valve appears to be working fine.

Would it be better to set a timer for the How water rather than constant?

Hi,
It’s a main boiler not sure exact model but only a few years old the customer says.

I did flick the case off to check the stat on the boiler which was set about 3/4 up. I tried turning this right down but didn’t seem to effect anything.

I did think has this become faulty. But surely the cylinder stat would still cut in and out at the correct temp? Plus the boiler isn’t that old surely the stat hasn’t gone already.

Cheers

 

[Sharp Point]

Cylinder stat faulty, way out of calibration?

 

[shyguy2005]

Cylinder stat faulty, way out of calibration?

That’s what I thought so fitted a new one and still the same....?!

 

[shyguy2005]

Also to throw a couple more things in there :-

The cylinder 1/3 up front bottom doesn’t seem particularly that hot compared to how hot the water is actually coming out at....

The 3 port valve seems very hot on the heating side even tho there’s no call for heating while hot water demand is calling.

When I was there I also swapped a some valves in a towel radiator nd noticed the water was shockingly brown! Clearly heating was never powerflush when boiler was fitted a few years back. Tank also full of crap.

So I was thinking potentially the cylinder coil for hot water is blocked/sludged up so only top half of cylinder is getting hot also 3 port valve is passing through heating as well therefore letting the boiler loose some heat to keep it running instead of it over heating?

The customer also mentioned a rad in the cloakroom comes on with hot water...... which I thought could’ve related to 3 port valve stuck or that rad on hot water circuit.

 

[townfanjon]

Basics , what temp is the HW at the tap ?

 

[Ric2013]

Basics , what temp is the HW at the tap ?

Yeah, the temperature required to keep the hot water hygienic is too high to be considered a comfortable temperature. I fitted a new cylinder to an existing system for a friend once, set the DHW stat to give a measured 59°C at the cylinder outlet (should be 60, but I felt that within one degree was close enough, considering the accuracy of my thermometer).

Friend complained that the water was far too hot at taps and could this be adjusted down? Taps were not mixers.

I explained the legal requirement for 60°C, and suggested TMVs. But I also explained that it is theoretically possible to turn the DHW stat down further and that, in fact, mine is set to 55°C at home, but that I wasn't prepared to do it myself.

My point being that, when the legal requirement for 60°C storage temperature is met, the tap water probably will be too hot and people will complain if there are not TMVs at taps.

 

[shyguy2005]

Basics , what temp is the HW at the tap ?

Not sure exact temp exactly. But can bear hand under it after say 5-6 seconds. Clearly something wrong.

 

[Sharp Point]

How old is the cylinder and are you in a hard water area?

 

[shyguy2005]

How old is the cylinder and are you in a hard water area?

Not in a hard water area. Tank doesn’t look that old , is insulated with foam. Say max 10 years. But as I say the heating water was shockingly brown. Like a pint a brown ale.

 

[Lambed84]

You need to confirm the actual temperature at all outlets before you go changing parts.
If cylinder stat is set to 60 I'd expect to see that temperature +/- 2° at the outlets.
As previously mentioned if you turn the stat down the boiler goes proves the motorized part of 3 port is working as it should.
Open vented systems tend to get murky quickly due to the nature of letting in air and muck.

 

[townfanjon]

Not sure exact temp exactly. But can bear hand under it after say 5-6 seconds. Clearly something wrong.

Apologies I cant stop laughing at your reply ... buy a bloody temp probe , come on !!!! Lol

 

[shyguy2005]

Apologies I cant stop laughing at your reply . buy a bloody temp probe , come on !!!! Lol

Lol. Couldn’t bloody find the thing in the van . One of those weeks where just racing round and no time to put things back in order on the van.

 

[sammathias]

Setting the cylinder stat to 60 degrees, your furtherst draw off will probably be dishing out 60+ degrees, up on experience if your only able to hold your hand under a tap for 5-6 seconds then that seems accurate . Grab yourself a temperature probe to rule out the cylinder stat first tho.

 

[sammathias]

Picture of cylinder and stat?

 

[shyguy2005]

Setting the cylinder stat to 60 degrees, your furtherst draw off will probably be dishing out 60+ degrees, up on experience if your only able to hold your hand under a tap for 5-6 seconds then that seems accurate . Grab yourself a temperature probe to rule out the cylinder stat first tho.

Is it possible then that the top of the cylinder to be considerably hotter than the lower where the cylinder stat is?
Therefore cylinder stat is calling for heat at 60c but the top of the cylinder reaching much higher ?

 

[shyguy2005]

Picture of cylinder and stat?

Waiting to hear back from customer about time to get back over there. So can take picture then.

 

[sammathias]

Well if cylinder stat is placed 1/3 up cylinder and is actually touching bare metal and set at 60 degrees top of the cylinder will be potentially
65-70, then obviously temp loss through pipework to outlet. Temperature probe will confirm this...I mean it's probably working fine, I'd like to see anyone hold their hands under like 55 degrees for longer than you stated.