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Running out of hot water


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So, wife had a shower, washed hair face mask etc. She says around 15 mins max. Around 10 minutes later I went to wash my hands and hot water is cold. Even now hot water is only lukewarm. We have the washing machine on but that's it.

 

With the best will in the world I don't think anyone can use 400litres in a shower. Do we need to ask Alto to come out and look at our ASHP?

 

We still don't have the solar up and running and excess diverting to the immersion as our builder tested positive for Covid today so now pretty much all of them are self isolating!

 

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An ASHP will usually heat the hot water according to a sensor supplied with the ASHP that is inserted into a thermostat pocket on the cylinder. Can you see anything that just looks like a thin wire disappearing into a small hole on the side of the cylinder?  If so post a picture, and an idea of how far up the cylinder that sensor is inserted.

 

When i set ours up first, I put the sensor into the higher of the 2 available pockets, which was half way up the tank.  that did not work well, because the ASHP would not sense the water needed heating until half of it was already used up.  It works a lot better in the lower pocket.

 

Even so, the lower pocket on my tank is about 1/3 of the way up, so again the HP won't know the water wants heating until 1/3 of it has already been used up.

 

Then remember a HP is much lower power than a normal boiler so takes longer to heat a tank of water than a boiler will.

 

Re shower usage, I measured our rainfall shower at something like 15L per minute full tilt and if used at full would use half a tank of water in not much over 10 minutes.

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14 minutes ago, ProDave said:

Can you see anything that just looks like a thin wire disappearing into a small hole on the side of the cylinder?  If so post a picture, and an idea of how far up the cylinder that sensor is inserted.

 

No small wire I can see you less you mean the black one? Water is back hot again so it may be the wife used all 400 litres which seems crazy.

 

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Edited by canalsiderenovation
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That could be it.  the temperature probe wire enclosed by a bit of flexible conduit.  The white wire at the bottom is the immersion heater.

 

That looks to be halfway up the tank and I don't see a lower down pocket to move it to.  If so the ASHP won't even know the tank is getting used up until half your water has gone.

 

Up to that point, the water in the tank stratifies, that is the hot water does not mix with the cold coming in at the bottom to replace the hot that is drawn off.  but as soon as the ASHP starts heating the hot water, convection starts within the tank, and that will cause the remaining hot water in the tank to mix with the cold at the bottom, so the first thing that will happen as the ASHP starts to heat the water, is the temperature of the hot water at the top of the tank DROPS before it then starts to heat up again.

 

EDIT hadn't seen the second photo, the sensor looks to be more like 1/3 of the way up the tank.

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That sensor is not at the bottom of the tank so I don’t believe you will have 400litres of hot water. My tank (350l )has two pockets fir thermostats at 1/3 and 2/3 from the top, I put it in the top pocket fir two of us but move it to the lower one if we have visitors.

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Wife now thinks she may have been in shower over 20 minutes so it could be she completely used up all the water! This hasn't happened when I've had a big bath and she had the large showerhead on and the Mira shower is really powerful.

 

I should have got on the app whilst she was in and adjusted the temperature to cold.....

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Depends what Mira shower you have, over 20 minutes could definitely use it up...  could be up to ~15 l/minute

 

With ASHP, presumably running close to 100% hot water usage with minimal cold water mixing. 

 

I think the break even between a bath and a shower is around 10 minutes, at most 15 minutes.

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  • 3 years later...
On 11/01/2021 at 18:55, ProDave said:

That could be it.  the temperature probe wire enclosed by a bit of flexible conduit.  The white wire at the bottom is the immersion heater.

 

That looks to be halfway up the tank and I don't see a lower down pocket to move it to.  If so the ASHP won't even know the tank is getting used up until half your water has gone.

 

Up to that point, the water in the tank stratifies, that is the hot water does not mix with the cold coming in at the bottom to replace the hot that is drawn off.  but as soon as the ASHP starts heating the hot water, convection starts within the tank, and that will cause the remaining hot water in the tank to mix with the cold at the bottom, so the first thing that will happen as the ASHP starts to heat the water, is the temperature of the hot water at the top of the tank DROPS before it then starts to heat up again.

 

EDIT hadn't seen the second photo, the sensor looks to be more like 1/3 of the way up the tank.

I have a similar problem, Would it be not possible to turn up the hot water temperature before a shower? Sureley having a little hotter water at the start could help and heat pump would already be providing hot water.

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1 hour ago, Cyberfruits said:

I have a similar problem, Would it be not possible to turn up the hot water temperature before a shower? Sureley having a little hotter water at the start could help and heat pump would already be providing hot water.

If you run out of water 4 things to do

 

Heat it hotter - needs more cold water to mix down to correct temperature - increases the effective volume of hot water

Heat it more often - let it heat when it needs, to little and often.

Reduce flow at outlet or time used, your using to much water

Get a bigger cylinder - your cylinder is too small for your lifestyle or number of people in the house 

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