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Author Topic: Heat Pump Install @ Courtiestown  (Read 10116 times)
TT
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« Reply #90 on: December 31, 2017, 03:24:09 PM »

The manual states the gshp has a 5kW immersion, so it must be a commissioning issue if this and the immersions on the heat store cant deliver decent DHW
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pdf27
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« Reply #91 on: December 31, 2017, 06:16:54 PM »

Just to get this straight, we have a thermal store:
  • 300 litres capacity
  • Maximum temperature 58C
  • Delivering water at 50C
  • Instantaneously heating cold water delivered at ~5C
  • Using a coil heat exchanger to do so

That isn't going to have a lot of capacity within it - the store is filled with water, meaning 300 litres cooling through 8C is equivalent to 53 litres being warmed through 45C. I would really question the use of a thermal store in this application - because you're using a heat pump the headroom between the minimum usable temperature and maximum deliverable temperature from the heat pump is tiny. They're presumably doing it to avoid the need for a Legionella Pasteurisation cycle as you would otherwise have with a standard cylinder, but heating to 60C once every week or two using an immersion heater would hardly be a big impact.
One caveat here - the performance of a unit using a counter-flow heat exchanger taking feedwater from the top of the store and returning it to the bottom will be significantly different. Because the water is returned to the tank at something close to the feedwater temperature, far more heat can be extracted from a given volume of water and thus the equivalent store size is much larger.

The reality is that things aren't as bad as that calculation makes out - showers will be thermostatically controlled and so are unlikely to see any impact before the water supply drops to 40C, giving an equivalent capacity of ~150 litres (2-3 decent showers). I still think a separate hot water tank with a weekly Pasteurisation cycle off the immersion heater would be a far better solution in your case however.
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brackwell
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« Reply #92 on: January 01, 2018, 09:07:38 AM »

The Mira Adept shower is preset to deliver water at a maximum of 41 degrees and experience to date shows it needs the 55 degree hot water setting water to operate properly. Mira recommend 60 - 65 degrees supply with a minimum recommended deltaT of 12 degrees C between hot water supply and shower outlet. That being the case the minimum inlet hot water temperature would need to be 53 degrees C.


I really do not get this statement at all.  For yrs i have used therm..mixing showers and i set the tank temp to give the shower temp i want when the mixer setting is almost at max hot. My tank temp is 42C in general but have had a shower with tank temp at 40C and shower on max.

I do not understand what those booster moments are all about,they seem a complete waste of time as shortly after the tank temp was back to where it was.  I would completely forget the booster idea and fit a inline water heater (https://www.toolstation.com/shop/Plumbing/d20/Water+Heating/sd3105/Stiebel+Eltron+Electronic+Instantaneous+Water+Heater/p41729)  close to the shower head. This will boost and ensure a hot shower whatever the circumstances and very min energy input and not destroy the COP.  This will improve efficiency and therefore capacity of your system.

Ken
« Last Edit: January 01, 2018, 09:25:05 AM by brackwell » Logged
linesrg
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« Reply #93 on: January 01, 2018, 03:54:10 PM »

Good Afternoon All,

The replies are appreciated.

Just to clarify things the DHW comes from the 229ltr tank within the heat pump enclosure.

I have run a test in the last three hours. I set the Immersun on boost to heat the EHS. It took about 2.5hrs to heat it from 19 to 45 degrees thus using circa 6.75kW of electricity. At this point the heat pump made the EHS 'active' as the water circulating in the radiator circuit was 40 degrees. Thus I don't see that heating the EHS serves any useful purpose as far as alleviating load on the heat pump in the production of DHW is concerned.

The manufacturer's operating instructions are what I quoted for the operation of the shower. I don't doubt the shower would work by supplying it with water at 45 degrees but this would be at the expense of using a larger quantity of 'hot' water from the tank within the heat pump. Would it manage both boys getting a shower without the second person getting 'short changed' as the hot water in the heat pump tank was diluted by incoming cold water?

I could set the heat pump to not start re-heating the DHW until there was a larger dt than the default 5 degrees?

We had another instance of insufficient hot water for a bath last night. Both boys had had a shower. The heat pump showed the DHW was still at 58/ 57 degrees. I knew from experience that this simply wasn't possible (I wold guesstimate that the boys must have used at least 100ltrs of hot water in their showers) and, as I've suggested already, I think one of the temperature sensors in the DHW tank is less than ideally located. SWMBO certainly didn't get a bathful of hot water (again).

The installers have limited the heat pump to 40A (about 9.2kW?) and the electric heater function to 2.9kW. As a matter of interest I've raised the electric heater limit to 5.5kW to see how this might impact the DHW heating process.

Fitting an inline heater kind of defeats removing the electric shower in the first place?

Clearly, it seems, a degree of compromise is involved in running the household on a heat pump? I'm sure we'll get used to it!!!

All further comments/ observations welcome.

Regards

Richard
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16off BP380 on a Lorentz tracker/ SMA SB2500, 16off Chinese 80W/ SMA SB1700, 16off BP380/ SMA SB2500. CTC GSi12 heat pump/ Gledhill ASL0085 300litre EHS/ 3off Navitron 4720AL solar ET panels and an Immersun T1060/ T1070/ T1090 (+ planned 7off 235W panels).
Countrypaul
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« Reply #94 on: January 01, 2018, 04:30:30 PM »

The inline heaters I looked at would only heat the water if it was below a set point, so for example, if it was below 45C they would heat it to 45C, if it was already above 45C they did nothing.

My understanding is that most electric showers would not work with warm water, this may no longer be true, or maybe it was just the ones we loooked at a long time ago.

The inline heater would work for the bath not just the showers, which might be more important to the peace than just working for a shower, in fact the inline heater could work for all DHW deending on how your plumbing is arranged and whether you wanted it to. Should the HP fail again it would leave you with a backup option. One you get the HW management around showers and baths resolved you could obviously then leave it switched off.
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pdf27
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« Reply #95 on: January 01, 2018, 04:36:48 PM »

Just to clarify things the DHW comes from the 229ltr tank within the heat pump enclosure.
Ah, OK - that makes rather more sense.

We had another instance of insufficient hot water for a bath last night. Both boys had had a shower. The heat pump showed the DHW was still at 58/ 57 degrees. I knew from experience that this simply wasn't possible (I wold guesstimate that the boys must have used at least 100ltrs of hot water in their showers) and, as I've suggested already, I think one of the temperature sensors in the DHW tank is less than ideally located. SWMBO certainly didn't get a bathful of hot water (again).
Is there any reason to think that the sensor is in the wrong place rather than out and out faulty or incorrectly wired? Essentially you've taken half the hot water out of the tank but the system is showing none gone and thus no attempt will have been made to reheat the tank.

Fitting an inline heater kind of defeats removing the electric shower in the first place?
If would if you put the inline heater on the cold line. They're thermostatically controlled though, so if you put it on the hot line it'll only kick in after you run out of hot water and provide just enough heat to stop the shower running out of hot water. So normally there won't be any power consumed, but when you do run out of hot water it's effectively the same as having the immersion heater on in efficiency terms. At 300 or so the cost is pretty modest compared to other ways of keeping the wife happy...
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rogeriko
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« Reply #96 on: January 01, 2018, 04:59:15 PM »

The hot tank sensor is no doubt towards the top of the tank, therefore if you need a full tank of hot water you must fit a destratification pump to circulate the water from the top down to the bottom. This will solve all your problems. We have done this on several heat pumps where they want baths. Dont forget virtually all heat pumps are made in europe where they do not have baths, just showers. They are not designed for filling baths. Just connect the pump between the DHW flow and the cold return, make sure there are not any valves on the hot flow and dont forget to fit a one way valve.
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brackwell
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« Reply #97 on: January 01, 2018, 05:00:46 PM »

Paul just beat me to it.

A normal instant shower uses the power that it is  -9kw ? and dribbles at sometimes as low as 3 L/min because it is heating cold water and it is difficult to use them with preheated hot water as they will lock out as a safety mechanism

There will be many days during the heating period when just a little bit of energy at the last minute will get it to the required temp.  You do realise that the output temp is controlled by changing the current not by varying the flow rate as in a normal leccy instant shower. For the majority of the year you will not be using any leccy at all although i would always keep the HP tank at 35C to get better COP and just add the little bit at the end as and when. The cost savings can be significant because
1) you are not murdering the COP or adding immersion heat
2) you are not holding water at a elevated temp and thus larger heat losses
3) You will never not be able to supply hot water unless you have no leccy
4) You are not creating hot water just to dilute it with cold.

The inline heater will be cheaper than what you are doing at the moment.

There is every reason to change your instant shower.

Ken
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linesrg
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« Reply #98 on: January 10, 2018, 08:08:59 AM »

Good Morning All,

Thanks for the comments/ suggestions. I do intend querying CTC as to their suggested solutions as there is simply too much 'user intervention' currently.

I accept that there will be an element of learning to live with some of the 'limitations' of having the heat pump installed, it would be somewhat ironic if the solution was the fitting of an inline heater having effectively removed an inline heater (in the form of the electric shower) in the first place!

Regards

Richard
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16off BP380 on a Lorentz tracker/ SMA SB2500, 16off Chinese 80W/ SMA SB1700, 16off BP380/ SMA SB2500. CTC GSi12 heat pump/ Gledhill ASL0085 300litre EHS/ 3off Navitron 4720AL solar ET panels and an Immersun T1060/ T1070/ T1090 (+ planned 7off 235W panels).
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« Reply #99 on: January 16, 2018, 03:36:37 PM »

Good Afternoon All,

The installers turned up this afternoon to carry out both the annual service and carry out a third flush of the Solar ET system. I know the ground loop took something like about six visits before the air was eliminated.

Our friendly neighbourhood pig farmer, what rents our field, is currently spraying pig pooh - can't wait for the weather to warm up..........

Regards

Richard
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16off BP380 on a Lorentz tracker/ SMA SB2500, 16off Chinese 80W/ SMA SB1700, 16off BP380/ SMA SB2500. CTC GSi12 heat pump/ Gledhill ASL0085 300litre EHS/ 3off Navitron 4720AL solar ET panels and an Immersun T1060/ T1070/ T1090 (+ planned 7off 235W panels).
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