I need a new Hot Water only System

[Swynol]

Wondering if anyone can comment and help me out.

I have a 1000ltr thermal store which my solar thermal and heat pump store its 'heat' 9 or 10 months of the year these 2 systems provide all the heat for heating and our hot water needs in a 4 bedroom house.

However in the coldest months there isn't enough hot water available for a shower early in the morning 6am. at around 9am there is enough hot water again. I am now fed up of cold showers and want ideas on what i can do to have hot water early in the morning.

My ideas so far.

1. a 50l electric water unvented tank in the attic which feeds from the hot water from the thermal store. So the heater will only need to heat the water from 30c to 40-45c. i obviously only want the 3kw heater to run in the morning when its needed.

• Problem 1. I would need a bypass valve so that when the thermal store water is hot enough it doesnt need to run through the electric water heater.
• Problem 2. is a 50l tank big enough to serve 2-3 showers in the morning with roughly 15mins between showers?

2. an electric insantanious inline heater. i am only on 1phase electric so biggest i can go is 13kw i think. i would need to run new cable (16mm) to the location of the heater. i know these slow the flow but at 5l/m i think this would be ok. Again i would use the hot water out from my thermal store so it would only need to heat from 30c. In the warmer months i would have this turned off.

• Problem 1. expensive to run
• Problem 2. running a new cable

3. LPG Combi. so i dont have mains gas. could i use a lpg combi boiler for DHW only. again running the hot out from my thermal store to the combi. the combi would only need to be on in the early mornings so at most 30mins a day to heat from 30 to 40-45c~. would i be better off using the 47kg bottles, not sure how many of these i would get through in 2-3months? or get a smallish tank installed outside? This would also benefit us as if we have a power cut we would still have hot water as everything else in the house is electric.

• Problem 1. Most expensive to install
• Problem 2. on sure of ongoing costs of bottles
• Problem 3. bottles or having a tank installed.

so that my problem, any help would be much appreciated.

 

[woodbine]

You don't need to go to the expense of buying and maintaining a combi, as in option 3. My brother lives out in the sticks and has just fitted an instantaneous LPG water heater. Provides instant mains pressure hot water, just as a combi.

https://www.mrcentralheating.co.uk/vokera-easi-flo-plus-28kw-lpg-water-heater-and-flue#.WF0-ppVvjcs

 

[Roger928]

ESBE, Intasol and Grant make valves for combi boiler diverting. Usually fitted with about five ports.
Not allowed to supply an unvented cylinder with hot water so that only leaves a thermal store. I assume you have a plate heat exchanger or an internal coil fitted to your current thermal store?

 

[Swynol]

i will take a look at the instant lpg heaters thanks.

I understand about the unvented cylinder. and yes i have a thermal store with 2 coils (one for solar thermal, one for heatpump). i then have a fresh water module which passes mains cold water through a heat exchanger to pick up heat for DHW, i wanted to put the heater on the outlet of the heat exchange on the DHW side.

 

[Swynol]

@woodbine does it cost much to run? i know its a difficult question to answer however i only need to heat the water from 30c to 40c and it will only be required for around 30mins a day for 2-3 months of the year.

 

[woodbine]

@woodbine does it cost much to run? i know its a difficult question to answer however i only need to heat the water from 30c to 40c and it will only be required for around 30mins a day for 2-3 months of the year.

Not sure of exact costs, as it's not the only LPG appliance using the tank. Remember him saying that it worked out cheaper than his old electric immersion cylinder. I realise that's not much help.

 

[simond]

All this talk about heat pumps, the thing the punters are never told about is the reheat time on the HW when the weather is cold.

So you end up having to augment the system with something very much along the lines of what you would buy if you hadn't chosen the heat pump option in the first place.

The things have very little value in most domestic situations, and with the new FiT proposals their combined massive load at peak times will further destabilise the electricity grid. It's on the edge as it is.

Unsurprisingly, you've got one part of the UK Government promoting reducing electricity consumption, and another part incentivising the rich (with taxpayers money from the poor) to install this crap and add additional load to the National Grid.

All this so called green rubbish is a nefarious and devious way to make the rich richer and the poor poorer. Only the wealthy can afford to stump up the high capital cost of a heatpump. But they will only do it when they can see a return on it over the next 7yrs, to be paid by the peasants in the form of an annual kickback levied on their electricity bill.

As it is, we're all getting shafted £240 per meter to put these useless 'smart meters' in; every single one of my customers who have had one have been underwhelmed by how useless they are. But we are all being made to pay for them as a surcharge on our bills. So much for the advertising saying they are 'free'. That is a lie.

I can feel a letter to The Times coming on.

 

[Roger928]

That's very true Simond.
I've always said that where ever you get the government involved with subsidies then it not viable.
Though my brother heats his home with a gshp.
A separate hp integrated with an unvented cylinder heats his hot water.

However it uses the ufh loop as the collector which will be providing 30c on many occasions to the evaporator.
So its acting as a "two stage temperature lift" system provided its timed to operate in tandem with the gshp.
Not sure how far that one lifts the temp but obviously its fitted with an immersion. His running costs are low. But of course his new build home had insulation well above BC standards. Any boiler would probably have given him low running costs.
He has no huge buffer/thermal store/accumulator (or what ever you like to call it) fitted.
And he has no heat meter fitted and is not receiving subsidy payments from tax payers.

 

[Roger928]

This is the unvented cylinder he has fitted..........
http://www.hautec-waermepumpen.eu/gb/Prospekte/03_Hautec_Warmwasser-Wärmepumpen 2015.pdf
He doesn't live in the UK so G3 doesn't apply.

The hydraulic layout is schematic 12.3..
http://www.hautec-waermepumpen.eu/d...rmepumpen/Bedienungsanleitung HWBW-K-2014.pdf

They don't provide installation manuals in English.

 

[Swynol]

thanks for the input. Just to add my input on the heatpumps situation.

So as i said above i have a large solar thermal setup, 8 panels. Yes it was expensive to fit but i would say it provides all my hot water and heating needs from March to October. In that time the heat pump may fire up a hand full of times. I have a 4 bedroom house with a large entertainment room and attached garage. underfloor heating downstairs almost always set on 22c. the family has at least 2-3 showers a day and at least 1 bath if not 2. So using alot of hot water. In the summer months the solar collectors reach around 180c which heats the water in the tank (1000ltrs) to 80-90c (top and bottom).

So the heat pump. this usually kicks in late Nov when the water in the tank is only around 40c. It usually boosts it to a max of 55c (top of tank). It usually reaches 55c around 8.30am and keeps it at this temp all day until around 10pm when the heatpump cant quite keep up the heating demand after we have just ran 2 baths. So by 6.30am my usual shower time the tank is only around 40-45c. My thermal mixer shower adds a bit of cold and my showers are now not warm enough.

All my house runs off electric. Some items in the house that consume alot of electric - large double range cooker, 4ft Marine fish tank, TVs with amps in most rooms, server rack running 24/7, wife and 2 daughters using hair dryers and straighteners.

So my monthly electric price is £120. However with my PV and RHI i get around £1000 back every year. So my yearly electric bill is around £400 which i think is quite reasonable on a 4 bedroom with alot of extra rooms.

 

[Roger928]

Fit an oil or gas boiler and heat the top section of the thermal store. Fairly easy to do.

 

[Roger928]

Nov when the water in the tank is only around 40c

The fresh water module won't deliver 40c. It might give you 35c at best.
That's where delivering the hot water directly to the taps from the cylinder has its benefits.