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Worcester Bosch 420 CDi hot water problem upstairs
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terry.sh...@gmail.com
Oct 24, 2017, 2:19:36 PM10/24/17
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Hello All.
As per subject line, I am having trouble drawing satisfactorily hot water upstairs in my house. Downstairs, the kitchen and bathroom hot taps supply water that is plenty hot enough. Upstairs (shower, bath, basin taps), the hot tap/shower water temperature is often lower than is desirable (but sometimes works fine). A notable aspect of the problem is that running a cold tap can cause the hot taps (separate hot and cold, not mixers) or shower temperature to increase.
My mains pressure is 3-4 bar (varies). The pressure is high-ish, but within spec for the boiler. However, noting the temperature-increasing effect of running a cold tap, I can't help but think that the problem is pressure-related and more particularly, that it relates to the pressure change when hot water is drawn. Upstairs, with a head of water higher than downstairs, the percentage pressure drop, on opening a tap/valve, will presumably be lower than for a downstairs tap/valve. However, when a cold tap/valve is opened somewhere in the house, boiler inlet pressure is reduced and then, presumably, the percentage pressure drop when an upstairs tap/valve is opened is increased. Might it then be worth my while trying a pressure reducing valve on the boiler cold water inlet?
To be clear, the problem is not that the upstairs taps/valves allow a flow that exceeds the boiler's heating capacity. With a cold tap running, I can get a greater flow of hot water from an upstairs hot tap than at *any* setting of an upstairs hot tap, running alone.
Advice appreciated.
Regards.
Terry.
As per subject line, I am having trouble drawing satisfactorily hot water upstairs in my house. Downstairs, the kitchen and bathroom hot taps supply water that is plenty hot enough. Upstairs (shower, bath, basin taps), the hot tap/shower water temperature is often lower than is desirable (but sometimes works fine). A notable aspect of the problem is that running a cold tap can cause the hot taps (separate hot and cold, not mixers) or shower temperature to increase.
My mains pressure is 3-4 bar (varies). The pressure is high-ish, but within spec for the boiler. However, noting the temperature-increasing effect of running a cold tap, I can't help but think that the problem is pressure-related and more particularly, that it relates to the pressure change when hot water is drawn. Upstairs, with a head of water higher than downstairs, the percentage pressure drop, on opening a tap/valve, will presumably be lower than for a downstairs tap/valve. However, when a cold tap/valve is opened somewhere in the house, boiler inlet pressure is reduced and then, presumably, the percentage pressure drop when an upstairs tap/valve is opened is increased. Might it then be worth my while trying a pressure reducing valve on the boiler cold water inlet?
To be clear, the problem is not that the upstairs taps/valves allow a flow that exceeds the boiler's heating capacity. With a cold tap running, I can get a greater flow of hot water from an upstairs hot tap than at *any* setting of an upstairs hot tap, running alone.
Advice appreciated.
Regards.
Terry.
John Rumm
Oct 24, 2017, 3:02:39 PM10/24/17
to
On 24/10/2017 19:19, terry.sh...@gmail.com wrote:
> As per subject line, I am having trouble drawing satisfactorily hot
> water upstairs in my house. Downstairs, the kitchen and bathroom hot
> taps supply water that is plenty hot enough. Upstairs (shower, bath,
> basin taps), the hot tap/shower water temperature is often lower than
> is desirable (but sometimes works fine). A notable aspect of the
> problem is that running a cold tap can cause the hot taps (separate
> hot and cold, not mixers) or shower temperature to increase.
Do you happen to know if this is a boiler that includes a flow regulator?
> As per subject line, I am having trouble drawing satisfactorily hot
> water upstairs in my house. Downstairs, the kitchen and bathroom hot
> taps supply water that is plenty hot enough. Upstairs (shower, bath,
> basin taps), the hot tap/shower water temperature is often lower than
> is desirable (but sometimes works fine). A notable aspect of the
> problem is that running a cold tap can cause the hot taps (separate
> hot and cold, not mixers) or shower temperature to increase.
--
Cheers,
John.
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| John Rumm - john(at)internode(dot)co(dot)uk |
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terry.sh...@gmail.com
Oct 29, 2017, 2:40:10 PM10/29/17
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Apologies for delay in picking this up. I've been away.
After consulting the installation manual, it seems that the boiler does have a flow restrictor/flow regulator assembly. Do you think that these components are prime suspects for the cause of the problems that I am having?
I've just been trying to get hot bath water again, this evening. Lukewarm only, no matter what the flow rate from the tap. Downstairs, piping hot through any of the hot taps, at any flow rate.
Regards.
Terry.
anonymousr...@gmail.com
Nov 8, 2017, 1:42:04 AM11/8/17
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just to tidy up my thread with a conclusion, it turns out that the problem was crossed hot/cold, caused by a knackered thermostatic shower valve. I didn't suspect it initially because the bath hot tap began producing only lukwarm water a long time before the shower valve properly failed (problematic hot water delivery was previously only intermittent, for the shower).
Basically, the shower valve was allowing flow between cold and hot inlets, even when turned off. This meant that when a hot tap was turned on, the flow from that tap was made up of boiler-heated water *and* cold water from the shower inlet, bleeding into the hot water pipes at the shower valve.
Regards.
Ant.
Basically, the shower valve was allowing flow between cold and hot inlets, even when turned off. This meant that when a hot tap was turned on, the flow from that tap was made up of boiler-heated water *and* cold water from the shower inlet, bleeding into the hot water pipes at the shower valve.
Regards.
Ant.
John Rumm
Nov 8, 2017, 3:53:10 PM11/8/17
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