Ditching gas, going electric immersion only, a wee project

BikingBud

What a great thread, thanks @Solarchaser I've really enjoyed reading this and it does stimulate different thought.

We are considering our options to change heating and DHW and it seems anything that is not mainstream is often immediately discounted without appropriate consideration of the holistic benefits.

This kind of set up would appear to be ideal for a self build where you made the decision to have integrated solar panels and can allocate space effectively for a plant room for the tanks and to drive EFH allowing a lower temp.  

Unsure we currently have space inside and not wanting to start on Tom, !!!!!! and Harry under the house I will likely keep watching without copying but please keep the thread updated as it would be good to understand how you assess it in the spring. 

Solarchaser

Thanks BikingBud.
I hope to update piece by piece especially in these colder months.

Solarchaser

Heedtheadvice said:

I would also opt (if I were not more lazy than you!) to extra insulate the tanks rather than remove underfloor insulation.

I chewed on this sentence and thought, yeah.
So swung by b+q tonight and picked up another roll of 200mm insulation and essentially used it to add strips of insulation to each part of the installation. 

It's got to be worth a try as it was -4C this morning, so I need all the help I can get

Heedtheadvice

It will not be for you owing to location but the met forecast I have just seen claims -15C in parts tonight.

Can you not take off all the insulation and warm us all up a bit...?

My opinion you are making the correct choice!

Solarchaser

Ahh well now, I have to say this week I've been eating some humble pie from Ken and Chris, and even from Reed_Richards as well as eating quite a bit of peak rate electric

It's been a disappointing week. 
I stated around a week ago I was dropping 2C overnight, however (as Chris said) I've dropped more as the outside temp has dropped, most of the last week has been sub zero, a few of the mornings have been -7C or less and I've noticed a 3C drop most nights, and even a 4C drop on Friday/Saturday and this is after adding the extra insulation. 

It should be said that I can only add insulation to the top and front of the tanks due to only removing enough soil/clay to allow the tanks in and they sit against a (vented?) support wall on the other side.

The extra insulation has helped with the central heating circuit bleeding out heat under the house, however it can't do anything with cold coming up from the ground nor anything blowing in through the support wall.

I noticed last night that 2 hours after the heating had switched off that the first radiator in the circuit upstairs and the first one in the circuit downstairs were actually warm to the touch, 2 hours later is bad, I confirmed with thermal camera that floor loops were still warm also that means that even with the double check valves and loops I have in the system, that when the pump kicks off, there is still a good amount of water moving around the system drawing heat from the tanks, and that will certainly be negatively impacting my overnight temperature drop.

The only way to stop this dead seems to be using motorised valves in supply and return to the central heating circuit, which I will look to do in the spring when adding another tank.

Observations about heat usage, first thing in morning in these minus days I'm using around 15-20kw in the first couple of hours.
Maintaining that heat throughout the day if the house is occupied is taking around 2.5-3kw/hour, and so I can maintain a steady temperature in the tanks with the central heating running by switching on one 3kw element through the eddi.
However if I don't maintain that 3kw of heat in the tanks and the temperature drops, then obviously 3kw is not enough to lift them back up, only to maintain,  so I think I need the control part of the heating circuit moved inside the house, (now its under the house) to be able to apply extra heat when comfort levels fall.

So far they haven't, but thats because ive been quite closely monitoring them, and my plan was never to watch the temperatures every day, just to have a dependable system.
As I type I've just realised I could have a PID controller with a minimum temperature to kick in and maintain and that would solve this.
Funny how sometimes reading your own words brings a solution you hadn't thought of.

Anyway, so for the last few days I've been boosting the eddi with 4-6hours of extra to maintain temperature,  which means an extra 12-18kwh on top of the 36kwh I add each night at off peak.

The house hasn't been cold, whereas with the gas central heating before it was quite common for the house to still feel cold with the heating on for several hours, so that's a win, seems to be mostly due to the pex floor loops in the livingroom and the large radiator in the back room.

I think I'm using around 55kwh in the tanks each day which is a bit if a concern.... but!
I decided to do a little test of a theory in terms of how much water was being used for a shower and so I took note of the temperature of both tanks before a family member went for a shower, I didn't tell them as I wanted to take a "normal reading" and the interesting thing for me was the second tank which is a preheat for water dropped 8.9C at the top  of the tank,  and the main tank did not drop at all, this means 2 things which I found quite interesting. 
1. The "solar" coil in the second tank is actually able to heat the water sufficiently that it could probably be used as a hot water provider on its own... though I'm not chancing it, just incase.
2. As its a 300L tank that means each shower is 2.8kwh, which was more than what I thought and pushes my water consumption for a day up to say 10kwh. Allowing the shower to be a little longer due to it being colder and folk wanting the warm feeling a bit longer, so 4 showers a day maybe 2.5kwh each.... its all a fudge factor, I'm just trying to get figures I can work with. 

Sooooo finding the positives, when I add the other tank,  I will excavate more of the soil around the tanks, to allow better access around them, I will add a gap between wall and tanks so I can fit some insulation between tank and wall, and I will have enough room to be able to add insulation under the tanks in a consistent way rather than the haphazard way I've tried to push some in just now.
When I add in motorised valves to supply and return lines for central heating that will stop dead any water flow that is simply happening due to the increased mobility of a circuit under pressure. (I could probably drop the pressure in the circuit to zero and that would stop the mobility,  but I think it would also cause a considerable increase in the noise of the central heating when running as there would be an increase in pump cavitation and general air in the pipes.

Finally (for now) I will reorganise the tanks in such a way as to always try and have the hottest water always in the main tank.
The way I have them just now is to try and keep all tanks at the same temperature so I have the destratification arranged to pull water from the mid point of both tanks and push it into the top, but it occurs to me (recently) that I really want the hotest water in the main tank rather than them all the same and so I will move to pull water from the bottom of the main tank and push it into the bottom of the 3rd tank, the top of the 3rd tank pushing its way into the bottom of the 2nd tank and then the top of the 2nd tank pushing into the top of the 1st tank, so the tanks will be arranged from coldest to hotest.
3rd tank coldest, 2nd tank middle and main tank gets the hotest water available as its the one which is doing the actual heating of the house.

I note that with current configuration the hotest part of the system is actually the top of the second tank, and thats only reduced with hot water usage, not with central heating usage which seems to not be maximising its use in terms of heating the house.

michaels

One thought, is the convection circulation actually a problem or is it just putting some heat into the house that you might have to anyway to stop it getting too cold at night?

(Plus in a way it is a good thing as it explains some of the 'excessive' heat loss during the overnight)

Also we were using 60kwh per day heat and dhw at the start of Dec and in the last few 'ice' days we have used 150kwh (about 6kwh per hour) - sounds extreme but I guess it is about 600w in each room which doesn't sound as bad.

Solarchaser

Holy moly moly 150kwh.
Man that makes me feel alot better,  thanks.👍

It's a problem because the heating kicks off at 11:30pm when everyone goes to bed, and it's only me who tends to be up later.
The first radiator downstairs is in the kitchen, I noticed going in for a drink at 1:30am and in my daughters room who was asleep 5 hours before, so really is wasted,  but yeah absolutely it's something I can recover as I improve and surely must represent 2 or 3kwh of that excessive loss.

Your post points out, in a similar way to QrizB 's post before that my focus on *averages* isn't particularly helpful for what I'm doing.
I took note of gas usage monthly, and octopus gas bills were monthly also, which gives an average over 30 days, but if you have a mild 15 days and a severe 15, the usage will average out, however for 15 days you have much higher usage, and that part I just need to accept really.
I guess I'm anxious to find out what my electric usage is vs previous gas usage

Apologies for previous post, children plural came up with homework questions while I was editing and I lost my train of thought several times

70sbudgie

You really need to know your standard deviations because understanding the spread of demand as well as the mean would probably be a lot more useful.

Solarchaser

Haha in relation to rooms, times of day, temperatures??

70sbudgie

I was thinking more of your intantaneous demand, though kWhrs over a defined period might be better. But there's no reason why you couldn't go into that detail. The winter is definitely the best time to be doing detailed analysis and planning, warmer weather is better for implementation.