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GSHP heating hot water options


(Moojuiceuk) #21

If we go for the low hanging fruit first, do you think you could still live happily with your DHW tank heated to 45C rather than 53C? (Please make sure your sterilisation cycle still happens once a week to 60C). Using an online calculator it says you use 2.6kWh of energy to heat 280L from 45C to 53C. Yes, the heat pump could have a COP of 2.5 to 3.0 when servicing DHW, but this still adds up over the course of a year.

Likewise, do you have the heat curve set on the UFH as low as you can tollerate, but high enough that the rooms stay warm?


(stephen krywenko) #22

do you have 2 unused 3/4’’ outlets one at the top one at the bottom just insert your own into it here how to build it – Howto build a Heat buffer Tank it handle up to 36 tubes or about 2 kw until the heat differential is too high and you loose to much to the surrounding


(Pete W) #23

we have quite a large, modern house with good insulation. But its around the same size as your two houses together Stephen - so much bigger tan an average UK house. That’s why i got a shock when comparing ‘average’ from the elec cos as they always say im a ‘high’ user, even though i have tried to go green!! Its good to compare someone with a similar size property.


(stephen krywenko) #24

yeah average home is about 1200. then again you can not compare 2 1200 to one 2400 as the the surface area is much bigger on two 1200 then a 2400…
download and install this program it free to use for 90 days ( oops they reduced it to 14 days now the older version had 90days)
http://www.remrate.com/home/license

put in all your house particulars , then you you can modify your house configuration add more insulation, insulate area that are not insulated etc… change temps for your geo thermal , add solar or solar water heaters and it will calculate what would be your yearly usage based on your location. and it is surprisingly very accurate, when every i do someone house it always within a few dollars of their actual bills for energy usage


(Pete W) #25

@moojuiceuk i think we would be happy to try a lower DHW temp, but was told to keep at 52 for the reasons you stated earlier. I havent seen a way to do a weekly sterilisation cycle on my heat pump, that would be useful :wink:

Have played a little with the UFH curves last winter, but will do some more this winter now i have a better understanding - lets see when the family complains :wink:


(Pete W) #26

@stephen here’s a photo of the top of my DHW tank

here’s my tank - designed for a GSHP

there are a couple of spare valves on top, not sure what for yet :wink:

https://www.wolseley.co.uk/product/worcester-bosch-greenstore-cylinder-for-ground-source-heat-pump-280-ltr-p624351-44/


(Moojuiceuk) #27

If the DHW immersion is switched via the heat pump controls then a sterilisation looks possible via the Worcester. Have a look for “Hot Water Peak” in your install manual. This looks like the option to use the compressor to heat water to 65C once a week on a chosen day. See below

My rule of thumb is 60C for one hour, once a week, so 1 hour at 65C should be more than enough.


(Moojuiceuk) #28

Just one other thing - that cylinder is an “unvented” cylinder, which means it is subject to G3 regs in the UK. Put simply, whoever installed it, did not do it safely. That red valve on the top of the cylinder is the factory fitted Temperature & Pressure relief valve. It is designed to let by and “vent” out water if the tank overheats and is over pressure (typically 7 bar / 90C but can vary). There should be a copper pipe coming from that Red capped valve, going to a tundish, then off outside.

If the cylinder does overheat, you’ll currently get a very wet and steamy garage / plant room and maybe someone scalded if they were near it when it vents!


(stephen krywenko) #29

well not sure what the little ones are the 3rd on in the middle could be your anode you could use that if you wanted. they generally do not make that many different tanks. I suspect you probably have others just hidden. does it have elements if it has top and bottom element you could use the bottom element as exit and the anode as entrance or if you do not use the elements use them as your top and bottom ports . or other options sidearm - not my favourite method heat exchange is fairly poor
e1cd0e9ca56e75d2bce14a63450b0668

a flat plate is the better second option, though you need a secondary pump but it exchange is much much better then side arm… side arm are only good if you have heat to waste like when used with wood boiler…
flatplateheatexchangerdual
hook the flat plate up roughly like the side arm then incase of secondary pump failure it still will work passively like the side arm
at 280l tank you need aleast 50 - 60 tubes evacuated system then you have plenty of hot water

is that your basement wall ? it uninsulated you could save 15% just by insulating that…


(Moojuiceuk) #30


Are you 100% sure your cylinder doesn’t already have integrated solar connections already present? Look at a screen dump from the manual…


(Pete W) #31

@moojuiceuk ah…well spotted! it looks like it does via the small pipes at the back!

also…thanks for spotting to installation error…its been there since 2011 ;-(. will get someone onto it!

@stephen looks like i could connect solar from the pipes moojuiceuk spotted - so could be back in the game :wink:


(Pete W) #32

@moojuiceuk well perhaps i should read the manual ;-). found the Peak setting and have set to once/week on a Friday. Also reduced DHW from 52 to 48. Didn’t want to go too far! will monitor and go lower if nobody notices!

It was buried in a customer level2 menu option i had to do atrick to get

Has a few other tweaking options may be worth playing with. Like
changing temp settings up and down overnight when we need a bit cooler. Am sure a few degrees wiill make a difference over time.

…shall get my wife to call you if she has a cold shower tomorrow :wink: :wink:


(Pete W) #33

@stephen well spotted on the insulation, but we are ok as this house has external insulation rather than internal, so its just that wall isnt rendered on the inside. Its a bit like a warm jumper over the house!


(Pete W) #34

you were right…my DHW cylinder is already ‘solar ready’

thats great news!

it says its compatible with their ‘Greenskies’ solar panels, but i bet it can work with others too.


(Moojuiceuk) #35

Excellent - fingers crossed Bosch Worcester also have a tried & tested hydraulic too.

Some useful info is in this document from the Energy Saving Trust in the UK. CE131 - solar water heating systems.pdf (712.1 KB)

Makes excellent bedtime reading!


(Pete W) #36

;-). Thanks!


(stephen krywenko) #37

if you want very nice controller can I suggest these guys. I’ve being dealing with them for a decade. they have tons of options on their controllers
http://www.shuangri.com/en/products/p5/

multiple cells, multiple pumps, web interface, ssr motor controls, they have integration for multiple heat sources and more .

they sell to you directly no problem
http://www.shuangri.com/uploads/soft/160903/1-160Z3142246.pdf would cover most configurations – system 13 would be what i use and I think what would work in your situation too…


(Pete W) #38

yes, 13 looks good. I think it’s probably only worth the investment if i can use for my undefloor heating tank as well as my DHW. That tank is a small 120L dedicated tank. Non potable water.

https://www.manualslib.com/manual/643764/Bosch-Primary-Water-Storage-120-Litres.html

Interested if I would be able to include this in the design as per Stephen’s suggestion and still meet UK regulations?


(stephen krywenko) #39

for that i would hook it up as as system 13 describes , i assume the circulating pump runs 100% of the time when the heating is enabled, then just put the flat plate on the cold return for your buffer tank and your done … if it does not run 100% time you can add in a second pump from the drain to the hot outlet. I assume there’s a mixing value to keep the temp circulating to your floor at a specific temp if not you might have to add one as your buffer tank will get much hotter then normal . but I would first try just using your existing pumps… maybe it will work fine … in summertime for all intents and purposes it just default to the primary tank if the circulating pump is not running to the buffer

for me my plumbing path is this Screenshot_20180820_134217

since I have 4kw of evacs on this system. in the morning it defaults to my secondary tank slowly warms that one then once that on is warmed it will switch to the primary where it then heats both tanks at the same time , then in the evening heats only secondary again until it shuts down for the night . as it tries to keep the tanks at equal temperatures which it generally does with in a couple degrees. - i have another 3kw going to a simple 200 l heat sink. - curious is the tanks inside the living area of the house or outside the living area ( ie attached garage)


(Pete W) #40

hi yes, there is a circulating pump on the UFH circuit. I believe it runs all the time as the GSHP is always monitoring flow and return. Even though hardly any used in summer. In fact, now you mention it I suppose i could switch off the UFH in summer? However i was told to keep the flow running to at least one room to keep the system in good health.

I dont think i have a mixing valve, as i think the GSHP manages the flow temperature to the UFH. If there is one its inside the GSHP unit.

I like the look of system13, and looks quite easy to convert mine to that.

My GSHP and two tanks are all in a plant room at the back of the house, all insulated like the house itself.