Ground Source heat pump

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Has anyone had any experience with installing a domestic hot water circulation loop to a domestic hot water cylinder being fed by a ground source heat pump?

The new house really needs to have a continuous HW loop as some draw offs are over 20m away from the plant room. As you all know, on a conventional system this would be fine as the HW cylinder would be over 60ºC and the circulation loop (which would typically be around 50ºC) can be easily achieved. However, with a ground source heat pump system the temperature of the cylinder would be maintained at around 45ºC, being raised to over 60ºC at pre-set times, once a week. But this would mean the HW temp would be circulating at perhaps 40ºC. The flow temp of the GSHP could be raised but this reduces the efficiency of the heat pump.

Does anyone see this lower temp as a problem, this must have been done before as GSHP's are installed on many large new build houses.

Cheers.
 
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But this would mean the HW temp would be circulating at perhaps 40ºC.

Not if timing a 60°C sterilization cycle to run say once per week, or a length of time determined by risk assessment.
 
Fit a grundfos comfort bronze pump with built in timeclock,set time clock to match the hot water period of the gshp unit that way it only circulates during the 60deg cycle
 
Fit a grundfos comfort bronze pump with built in timeclock,set time clock to match the hot water period of the gshp unit that way it only circulates during the 60deg cycle

Thanks for your comments, though if the circulator pump was only running during the 60 degC cycle would this not mean that the other times would not have the circulating HW facility, so only once a week would the water be circulating. Or will the 60degC water last a while?
 
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How about a small under sink instant electric heater to supply the remote hot taps. It has to be capable of inputting hot water from the cylinder. The electric heater gives instant hot water at the taps and cuts out when the hot water is through from the cylinder. This may be a cheaper way of running and installing. The circulation pump will cost to run and also extracts heat from the cylinder.

Most people oversize basin draw-off pipes. 15mm is way too large for most. A 10mm pipe from the cylinder to the remote basins and an electric heater at the taps could be a far cheaper way to run and fit.

I saw this in back to back an en-suite and bathroom. A lagged 12mm pipe was run from the cylinder to a small under-sink instant electric heater, then out to two taps on the two basins. The basins always had instant hot water with the electric heater cutting out quite quickly as the hot water came in from the cylinder, being set to under the hot water cylinder temperature. The lag of the hot water on the draw-off lags to baths and showers didn't matter as these are not used that frequently during the day.

Make sure all hot water draw-off pipes are lagged.
 
How about a small under sink instant electric heater to supply the remote hot taps. It has to be capable of inputting hot water from the cylinder. The electric heater gives instant hot water at the taps and cuts out when the hot water is through from the cylinder. This may be a cheaper way of running and installing. The circulation pump will cost to run and also extracts heat from the cylinder.

Most people oversize basin draw-off pipes. 15mm is way too large for most. A 10mm pipe from the cylinder to the remote basins and an electric heater at the taps could be a far cheaper way to run and fitting.

I saw this in back to back an en-suite and bathroom. A lagged 12mm pipe was run from the cylinder to a small under-sink instant electric heater, then out to two taps on the two basins. The basins always had instant hot water with the electric heater cutting out quite quickly as the hot water came in from the cylinder, being set to under the hot water cylinder temperature. The lag of the hot water on the draw-off lags to baths and showers didn't matter as these are not used that frequently during the day.

Make sure all hot water draw-off pipes are lagged.

This is a good idea in practice, however the instant water heaters provide very low water flow rates (unless you get a 9 or 12kW version, but 4 or 5 of them in the house could be a heavy draw on the electricity supply) the heat pump is suppose to save money!! They are also not great for kitchen sinks, and you tend to need spray/aerator taps with them.

Ground source heat pumps are presumably installed in large houses with the same situation having draw offs well away from the HW cylinder?
 
This is a good idea in practice, however the instant water heaters provide very low water flow rates (unless you get a 9 or 12kW version, but 4 or 5 of them in the house could be a heavy draw on the electricity supply).

The water flow rate on a basin does not need to be high, they are mainly for washing hands, not much else. The example I gave worked brilliantly and was cheaper to run, and install, than running a pump most of the time extracting heat from a cylinder.

the heat pump is suppose to save money!!

They are but why dump that money into the house via a long water loop. There is no definite way all depending on the house design. But by nature bathrooms cluster around the soil stack, so a 12mm pipe from the cylinder (or combi) only for basins using one instant electric heater at the point of use, is quite simple and highly effective. It cuts out very quickly. I have seen small, a few litres, unvented storage heaters do the same thing. Then instant DHW at the taps with no problems at all.
 
I like some of your thinking perfectionist.

I also agree that in big houses 15mm and worst due to old plumbing 3/4" hot water pipes are a big cost of water and heat (since the existing are normally unlagged).

in my house it is a certainty that my family run a hot tap in the bathroom to hand and face wash for insufficient time to get freshly hot water. I have solar heated hot water but it is wasted by a slug being drawn part way to the taps, never utilised, but left there to cool off over time. Total waste of energy.

Since one can't train women and children (at least the ones I have tried to train) to appreciate these values, and just use the cold tap, we have to think of a solution.

I have considered running 10mm lagged plastic.

Another idea I have, since our bathroom window is south facing, is to pass mains water through a window sized solar panel with sufficient capacity to fill a basin, and provide a 3rd tap, which the family would try to use first.

I also see that the energy saving of gshp is pointlessly lost in the described scenario, but I am not sure your solution is optimal either due to the high cost of the reheat at point of use.

The kitchen sink is the only one which needs hotter than 40 degrees, so vanity and bathroom basins could be supplied from the gshp heated cylinder using lagged small bore pipes, kitchen sink intercepted with 15 litre 3kw multipoint or gas multipoint/combi directly beside the sink. I think other people have found that the cost of running a dhw return pump is beyond the water rates saving, so small bore pipes would be cheaper to run, even if it would appear a little wasteful of water the cost to the user is less than the cost of circulating.
 
Use a bronze with a timeclock and thermostat set to 40° set the timeclock to turn off at night and during the day if nobodies at home.
Do not use an undersink water heater as any energy savings gained from the heat pump will be wasted
 
I also see that the energy saving of gshp is pointlessly lost in the described scenario, but I am not sure your solution is optimal either due to the high cost of the reheat at point of use.

The instant electric heater only operates when the tap is on. It heats instantly then cuts out when the hot water is at the taps from the cylinder or combi down a suitably sized basin draw-off pipe. The electric heater is not running all day as a pump would. I know the pump cuts out when the loop is up to temperature, but the loop will cool pretty quickly, even if lagged, due to natural circulation loop up the tees to the taps on basins and sinks.

In existing homes the electric heater is effective and practical as there is little upset to the house in ripping up floors to get a loop in.

The kitchen sink is the only one which needs hotter than 40 degrees, so vanity and bathroom basins could be supplied from the gshp heated cylinder using lagged small bore pipes, kitchen sink intercepted with 15 litre 3kw multipoint or gas multipoint/combi directly beside the sink. I think other people have found that the cost of running a dhw return pump is beyond the water rates saving, so small bore pipes would be cheaper to run, even if it would appear a little wasteful of water the cost to the user is less than the cost of circulating.

People go by rule of thumb and do not think hard enough. You have seen that unlagged 15mm pipe for basins is overkill.

Do not get me wrong. A secondary circulation pumps is ideal in many situations. It is not the only way to stop the dead-leg cold slug and also save on water and energy bills.
 
Use a bronze with a timeclock and thermostat set to 40° set the timeclock to turn off at night and during the day if nobodies at home.
Do not use an undersink water heater as any energy savings gained from the heat pump will be wasted

I don't think you got my point, Paul Barker did.
 
Anyway I would say get a solar panel to supplement the gshp or take over from it on sunny day.
 

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