no worries my heating operates at the same temp as the domestic water (your not suppose to consume hotwater in general anyways as in contains alot of leached chemicals that really not healthy for you and even showering can be quite unhealthy due to the fine mineral particulate ), if it was to operated at a lower them would place that on a closed loop,… as the temp diff between ~50C and ~30C is relative great for easy fast heat transfer.
here a break down --generally in the good sun for 8 months the water will heat to 60 - 68 c in the winter it might generally make it to 50 - 60 ( there is a 1 month period where 45 is about the top temp 2 week before and after winter solstice
I have two tanks in series ( tank1 - domestic ~100l - tank2- heat buffer ~300l), my solar controller handle both tank directing the energy to the cooler tank first then once thermal fluid passes the temp of the hotter tank it runs the transfer fluid through both tanks. my heat pump specifically heat the tank 2 as when you use domestic hotwater or the heating system is on. it cools that tank not the domestic tank. when the heat pump comes on it pull perhaps 10% from the domestic to maintain it temp. when the heating system is requires it follows this path buffer tank ( mid tank) to heat pump > to top of buffer tank 60/30 split to heating which returns to the cold inlet on the buffer tank ( bottom of tank) when no heating required it moves mid tank to top of tank - with about 10% moving to the domestic so even though I only heat the buffer tank to 45-47C when it runs through the heating cycle it generally heats the domestic tank to +50c. as the hotwater leaving the heat pump is generally around 55 c when it getting close to finishing it cycle which pretty much sterilizes the system for the most part . then generally every couple days the sun heats it up enough to be completely sterilized of any bacteria. and if it not sunny enough and if my hotwater is cool, it sterilized by the instant water heater. like I said 11 years in operation 2007 is when it was installed
I do have 2 water tanks. One services the DHW and one for the underfloor heating. The DHW tank is also Worcester Bosch, it’s a 280L tank, but only has one feed in from the GSHP. My underfloor stores at around 30degC and DHW at around 53degC. All delivered from the GSHP with a 3 way switching valve inside the unit. It does have a booster element, but that only came on once last year when we had a really cold night.
I see from the Worcester website that they now make a tank specifically to combine solar with a 2nd heating source. Greenstore Unvented Solar cylinders.
I’m reluctant to spend again o a new cylinder, so that option is not for me at the moment.
I will give them a call on Monday though to see what else they may have that works with my setup. I know they do flat panel solar but i don’t think they do evac tubes.
The high values in Nov-Apr are due to the GSHP generating DHW and underfloor. In the other months, although they are low, a lot of it still comes from the DHW needs. We have quite a lot of tech in the house so realise i’m a high user anyway outside of the GSHP. I’m using 10-15kwh/day to power non heat related stuff. In the summer months, the GSHP uses around 5-6kwh per day on water heating.
I clearly need to focus on the winter But i was interested in making at least a small difference on sunny days to reduce my energy usage for the GSHP. Stephen’s approach looked very interesting to me, and I do like the idea of the evac tubes. But maybe not compatable with my system.
I’ve looked at PV panels before, but my calculations make that not worth while for me - hence my looking at solar water heating.
my energy usage is similar to yours but the difference here is that this energy usage is for 2 1200sqf home ( and a greenhouse) on one meter and my average temp is probably a lot colder then yours ( pretty much split the usage in 1/2 for one home )-- April missing as they over estimated my usage so the next couple months the energy company average it out… I shut down the second house last april and do not plan to heat this winter as no one lives there any more
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?
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
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.
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
@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
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
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.
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!
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
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…
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 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
@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!
But i was interested in making at least a small difference on sunny days to reduce my energy usage for the GSHP. Stephen’s approach looked very interesting to me, and I do like the idea of the evac tubes. But maybe not compatable with my system.
