Immersion Diversion - Do you turn off your boiler in summer?

JimLad

Hi Guys!

Just wondering how you guys with immersion heater diversion on your solar panel systems have things set up?

I have my hot water to come on at 6pm for half an hour to top up the hot if its not a sunny day. The thermostat is set at just below the immersion, so if we get a good day the boiler wont need to fire up.

Most hot water in my house is used in the mornings with showers, so thats when we use the previous days hot up, ready for the sun to hopefully top it up again.

Is that the most efficient? I have heard some people say they turn off the boiler completely in summer and rely soley on the solar diversion?

ajbell

I haven't had to heat hot water with my gas boiler since February.
My iboost has given me enough hot water for general hot water usage including 2 baths a day. I expect it to continue until November.

EricMears

JimLad wrote: »

I have my hot water to come on at 6pm for half an hour to top up the hot if its not a sunny day. The thermostat is set at just below the immersion, so if we get a good day the boiler wont need to fire up.

Most hot water in my house is used in the mornings with showers, so thats when we use the previous days hot up, ready for the sun to hopefully top it up again.

Is that the most efficient? I have heard some people say they turn off the boiler completely in summer and rely solely on the solar diversion?

The crucial sentence there is :"if we get a good day the boiler wont need to fire up" !

If you switch the boiler off completely, you won't have that 'fall back' position. If we don't get a good day the second person to shower next day would get a rude awakening ! But perhaps they like cold showers ?

There's also another point worth bearing in mind. If you switch the boiler off completely, that will no doubt also switch off the pump that moves water around the boiler circuit. Four or five months of standing idle might well result in the pump clogging up when it's first run in autumn.

All in all, I'd say carry on as you are.

michaels

We turn the boiler hot water temp down to 50 from 60 and the lower immersion is on the iBoost set to 70 degrees. We don't get all the excess PV that way but can be certain that both morning and evening showers and baths will be hot enough. (We charge our EV in the day so mop up a lot of your PV that way).

I worry a bt about legionnaires in the winter and put the boiler temp back up to 55 or even 60 in december/Janauary.

JimLad

Thanks for your thought everybody. I think im going to keep on doing the same!

I need to turn the immersion down a bit actually as the water in the kitchen can get scorchio!

zeupater

EricMears wrote: »

The crucial sentence there is :"if we get a good day the boiler wont need to fire up" !

If you switch the boiler off completely, you won't have that 'fall back' position. If we don't get a good day the second person to shower next day would get a rude awakening ! But perhaps they like cold showers ?

There's also another point worth bearing in mind. If you switch the boiler off completely, that will no doubt also switch off the pump that moves water around the boiler circuit. Four or five months of standing idle might well result in the pump clogging up when it's first run in autumn.

All in all, I'd say carry on as you are.

Hi

We simply switch the DHW over from timed to manual and leave the boiler on so that the boiler runs the pump for a few seconds every day to prevent seizing ... doesn't help with the 2-way valves though, one of them usually needs a little manual assistance the first couple of times it's used each 'winter' .... we very rarely (/almost never) need to use gas to heat the DHW between mid-March & mid-November ...

HTH
Z

Alan_Brown

We have our immersion heater fitted at the top of the tank, and I noticed that on a good day, the immersion was switching off quite early. We have a blank at the bottom of the tank where I need to fit a second immersion, but in the meantime I set the existing one to switch off at 80C, with the high temperature cut off set to 85C.

It still goes off once it reaches temperature, but takes a lot longer to reach 80C. I'd obviously prefer to have the whole tank to 60C, but it's a good compromise for the time being.

For safety, we have a mixer valve on the hot water feed to keep the temperature at the taps to a maximum of (IIRC) 50C.

EricMears

Alan_Brown wrote: »

I'd obviously prefer to have the whole tank to 60C, but it's a good compromise for the time being.

Or, better still, when you do fit your second immersion heater element set that to 80 deg C (or even hotter) to get the whole tank very hot. Since you have a mixer valve on the DHW supply that's not going to risk scalding anybody.


If your diverter has two outputs, set it to heat top element first then bottom one when top is hot enough.

michaels

EricMears wrote: »

Or, better still, when you do fit your second immersion heater element set that to 80 deg C (or even hotter) to get the whole tank very hot. Since you have a mixer valve on the DHW supply that's not going to risk scalding anybody.


If your diverter has two outputs, set it to heat top element first then bottom one when top is hot enough.

Will your losses start to increase even with a well lagged tank if you go too hot?

EricMears

michaels wrote: »

Will your losses start to increase even with a well lagged tank if you go too hot?

Heat losses will of course increase with a greater heat gradient across the tank insulation. But those 'losses' would probably just be warming the fabric of the building so not really a loss at all.

Cash losses just don't exist ! We're talking about utilising the excess generation not buying electricity to heat the tank.

matty2767

For us it depends whether all the kids and wife have a bath/shower in the evening. If they do then there isn't enough time in the morning for the sun to heat the water before I need it, so we use the boiler to heat the water. Less than that then we are ok from solar. I guess if you have a big enough water cylinder to take you through the duller days you should be ok without the boiler but I would accept some use of it.

We have tried to have the boiler off auto since May but not been that successful TBH, really it's since beginning of July that we have been reliably using solar.

As an aside, since 30th March when we got our new iboost we have diverted 790kwh