Plumbing question!

heavymental

Hi folks, not been around these parts for a while but nice to see everything seems to be tickety boo.

I can't be arsed to sign up to a plumbing forum so thought I'd ask you lot!

Immersion heater failed a couple of weeks ago so the plumber came and stuck a new one in. Trouble is, temperature is fine but the volume of water it heats is rubbish now. What I mean is..... We used to get at least 2 good hot showers out of the tank and only needed to use a little bit of hot water and plenty of cold. Now, you stick the hot on full with a little bit of cold and only really get one decent hot shower before the temperature starts to drop. That's after the heater has been on for a good hour or so. I don't think there can be a fault with it as the first one malfunctioned the other day and he put a new one in. Same problem though, doesn't seem to heat very much water. Any ideas?

arthur_scrimshaw

Can you not turn up the thermostat on the immersion heater? Normally under the housing cover?

kev77

you can alter the temp on some immersion heaters, also is it the same KW rateing as the original one?

Stone Glider

As I understand it the immersion heater should be left on for much of the day. It isn't supposed to work like an electric kettle. The new heater may be shorter than the old one and as such heats a smaller portion of the cylinder. As they do say.... you had to be there. Good luck.

nikle

Could be your Plumber installed an Immersion heater thats shorter than the original.

Assuming the immersion "Boss" is located at the top of your cylinder a 17" immersion should heat half the cylinder, if its a Direct Cylinder with two or more immersion heaters located in the side..well it might be more involved.Get the Plumber back, its a fault.

heavymental

Thanks chaps...and particularly nikle....your first ever post on a cycling forum is to help me out with a question not remotely about cycling!

Trouble is, I'm not sure of the specifics of the original heater so I'm not sure if its been a like for like replacement. By the sounds of it...it isn't.

The heater is a Heatrae Pullin 27" gold dot immersion and its in a tank thats roughly 42" in height. Does that sound like the right element?

There is a thermostatic adjustment but on the last one, I turned it up a little and it cut out and had to be reset so I'm unwilling to touch it again. And like I said...no problem with the temp, just the amount of hot water we get out of the tank. It sounds like maybe he's just installed a shorter heater and maybe its not as powerful as the one that used to be in there.

I assumed that an immersion heater would be like a kettle and heat the whole tank of water up. How does it only heat the water above the length of the element? Surely convection currents would mean the whole tank is heated?

Stone Glider

Re. convection currents. The hot water is at the top of the tank, the cooler water is below it, that is more-or-less 'job done' as far as convection is concerned.

nikle

Hi,

Well I have lurked on off for a while as you do, thought I'd reply to this one as I'm a plumber & Cyclist!

27" is the longest heater element available for domestic cylinders, and if you have 900mm?
or so cylinder thats what the replacement should be. You could try isolating the pwer, remove top disconnect the 2 leads each side of the thermostat rod, remove thermostat, check the length- I suppose at least 12"( the dry pocket is not as long as the actual heater length)
or check it against the original if available.

Convection currents will only circulate in upwards directions....warm air or liquids are lighter more buoyant ..not downwards away from the heater .. it has to be the length as you say the
stored temp is ok. Just not enough volume.. difficult to be sure, They do now have the thermal cut out (red reset) to stop scalding,But they are really simple & it sounds like a crass error by the installer. Any way good luck .. too much typing for me, back to the undergrowth!!

heavymental

Hm well. It says 27" on the label so I don't know what the problem is if thats the longest available. I don't have the original element so can't be sure really what the difference between what's in now and what came out but I presume if 27" is the longest...that can't be the problem?

After christmas, when hot water is less critical, I'll try and turn it up a little and see what happens. Don't want to risk any problems as my housemates won't be happy if there's no hot water over christmas! Not that much can go wrong but you know.... Its not a serious issue, just means waiting a while between showers at the moment.

I'll go look at diagrams of convection currents now! I always thought there'd be movement of heat between the hot and cold water and gradually the whole tank would heated. You learn something new every day!

tri-sexual

i'm not a plumber but i have fitted immersion heater elements in the past,
my advice is to ring the plumber who installed the immersion heater element, explain your problem and ask what the fault is. he should advise you over the phone or should rememdy the fault for free.
immersion heaters are pretty basic things.
i will assume that the plumber has done the job correctly and have fitted the correct part, from your description i agree with arthur, turn up the thermostat. the water in the cylinder will be hotter so you can mix it with more cold water. it should go back to your original setting and your tank of hot water will last much longer. you cant really do much harm, if this does not solve your problem you can always turn it back to the current settings.

Tom Butcher

Yes like some of the above I'm thinking maybe the water is being heated to a lower temp so you are using more hot/less cold and consequently the hot doesn't last as long. I'm not a DIYer by temperament but I have installed a new immersion heater and they are pretty basic things.

Homer J

If he only changed the thermostat It's possible that it is too short. If it was the whole immersion heater it would come with the correct stat. As for the temp setting, they are pretty standard, set around 55 degrees. Best bet get the plumber back if you are not happy.
As for the whole tank getting hot it is only the top 1/3, it's called stratification.

Unless someone is taking longer showers???

heavymental

Thanks chaps. I'll try turning it up after christmas and see what happens. Don't really want to call the plumber back as its a rented property and we try and keep our heads down with the landlord as we're paying cheap rent! If we have hot water thats good enough but I will see if turning it up helps the situation.

Tom Butcher

Could the cold weather be having an affect - perhaps the cold part of the tank is colder ?