Immersion Problem?

whitelightrider

Right folks, need some advice before I lose my mind.
Have a 300l solar tank in the garage connected to an oil fired condensing boiler. Stupidly ran out of oil yesterday so no hot water. Switched on the immersion for an hour last night but the water was barely tepid. Set it to come on from 4am to 6am and just checked it there and the waters hottish, but not HOT if you know what I mean.

Does this sound like theres a problem? I thought 2 hours should be loads of time to get hot water using the immersion.

cormie

Check each thermostat is turned up fully, if you're heating from the bottom of the tank, which the night one would do, it'll take a while for it to get HOT, if you heat from the top of the tank it'll be much quicker.

whitelightrider

cormie wrote: »

Check each thermostat is turned up fully, if you're heating from the bottom of the tank, which the night one would do, it'll take a while for it to get HOT, if you heat from the top of the tank it'll be much quicker.

Hey Cormie,

Where would these stats be? At the side of the actual tank?
Ill check what they are currently set to and Ill adjust them up later today.

cormie

Yeah, there is probably two, it would look like this:


So just take off the cover if there is one and adjust to the desired temp.

It's probably cased in something like this, so just unscrew the black cover:

whitelightrider

Thanks for that Cormie. Ill take a look when I get home.

Should it still take that length of time though for the immersion to heat the water?
It was on for a full hour last night - 9pm to 10pm - cold water and from 4am to 6am - hottish water. Not exactly roasting for a shower.

cormie

I'm not sure exactly. Were you using the boost or did you just have the timer set for between 9-10 and 4-6? The first 30 degrees or so are the hardest to heat and then it speeds up after that apparantly

whitelightrider

cormie wrote: »

I'm not sure exactly. Were you using the boost or did you just have the timer set for between 9-10 and 4-6? The first 30 degrees or so are the hardest to heat and then it speeds up after that apparantly

Just had the timer set. Had a call from my other half there and she said that even though the immersion had been on for an hour last night, and 2 hours this morning, the water was just about warm when she had her shower at 8am. Surely that cant be right?

cormie

it could be, the thermostat could be set low and wouldn't heat it past a certain temperature. Best just to check it later and see what the story is.

whitelightrider

Ok just checked there and theres only 1 thermostat on the cylinder. When I removed the cover it is set to 60 but can go up to 80. Should I change it or leave it alone?
I still think there might be a problem though because theres no way the water was at 60 degrees this morning.

whitelightrider

Ok had my plumber take a look at things. He said that the immersion should heat the cyclinder in about 30 or 40 mins. Theres no way it would only get luke warm after 3 hours.

Put in a call to the electrician to find out whats going on.

Carlow52

AFAIK:

It takes 4.16kJ to heat one litre of water by 1 degree

4.16kJ is 0.00116kWh

so for 300 litres from 10C to 60 C is 17.4kWh

If the immersion is a 2kWh then it will take 8.7 hrs to heat up.

so 2 hrs here and there is just not going to do it.
---

the old immersion cylinders were about 30 gals or say 130 litres. with the immersion in at the top.

The solar 300l tank with the immersion in at the bottom....

whitelightrider

Carlow52 wrote: »

AFAIK:

It takes 4.16kJ to heat one litre of water by 1 degree

4.16kJ is 0.00116kWh

so for 300 litres from 10C to 60 C is 17.4kWh

If the immersion is a 2kWh then it will take 8.7 hrs to heat up.

so 2 hrs here and there is just not going to do it.
---

the old immersion cylinders were about 30 gals or say 130 litres. with the immersion in at the top.

The solar 300l tank with the immersion in at the bottom....

Thanks for the breakdown Carlow. Im going on what happened in the past when the oil boiler wasnt heating the water. It took at most 40 mins to give 2 showers worth of roasting water. 3 hours with the immersion on this time and the waters barely luke warm.

Carlow52

whitelightrider wrote: »

Thanks for the breakdown Carlow. Im going on what happened in the past when the oil boiler wasnt heating the water. It took at most 40 mins to give 2 showers worth of roasting water. 3 hours with the immersion on this time and the waters barely luke warm.

Coil in tank from oil could be 20 kWh output:) as opposed to 2kWh for immersion.

I have 2 by 3kWh immersions in my 300l and it takes for ever if I have to use them

whitelightrider

Carlow52 wrote: »

Coil in tank from oil could be 20 kWh output:) as opposed to 2kWh for immersion.

I have 2 by 3kWh immersions in my 300l and it takes for ever if I have to use them

Its weird because even the plumber said it should be hot after that length of time. Even the house we were renting would only take about 40 minutes to heat enough water to run a bath and the shower.

Carlow52

whitelightrider wrote: »

Its weird because even the plumber said it should be hot after that length of time. Even the house we were renting would only take about 40 minutes to heat enough water to run a bath and the shower.

much smaller tank, heated from the top

eoghan.geraghty

I have a 300 litre stainless cylinder for solar application and yes it does take 4 hours to heat the water to 60 deg with the immersion.
Do not increase the temp on the stat to 80 deg, you will likely scald someone.
The reason why your oil heats the water in 40 mins is because the heating coil is situated near the top of the cylinder so is only heating maybe 60/80 litres of water, your immersion element is near the bottom.
It may sound like a pain and expense to heat water for 4 hours to have a shower, but the cylinder should be so well insulated that the water is hot for 2 to 3 days, most solar ones are.

Had a similar situation only the other day.
The boiler pump failed, and all the water in the 300l tank cooled, got it back up to about 35c by tweeking the solar bypass thermostat then the rest of the way using the immersion.

Took about 4 hours, the solar buffer tank lost about 10c in the process, at this time of the year I only expect it to pre-heat the water before the boiler.

whitelightrider

Thanks folks. Looks like it might be normal enough so.
Dolanbaker, after 4 hours was the water hot enough to have a shower? Because after 4 hours ours was only lukewarm.

cormie

Just leave it on overnight for tonight, from 11-7 or whatever time it is and providing the thermostat is ok, you should hopefully have a full tank of 60 degree water that will last days and as long as it keeps warm enough, should heat much quicker with a little boost an hour/half an hour before a shower

dingding

http://www.thermtec.co.uk/geeza/geeza.html

An option could be to fit an external willis imersion heater to the tank.

This will heat the water at the top (outlet) of the tank at a very high temperature and may solve the problem.

I have one of these on a standard immersion heater and I find it excellent.

It heats a small ammount of water at the top of the tank to a higher temperature rather than as an immersion does heating the whole tank gradually.

whitelightrider

whitelightrider wrote: »

Thanks folks. Looks like it might be normal enough so.
Dolanbaker, after 4 hours was the water hot enough to have a shower? Because after 4 hours ours was only lukewarm.

Just about, but the water started @35c from the solar tank - it had a bit of a head start

cormie

Is all the water in the tank in the same container or are there two separate containers where there is a top and bottom heater? Is it not a bit silly having it all together, would it not be better to have a top part separate so it would heat without mixing with the bottom colder water?