Hot Water Tank Help

karlitob

Hi all,

Once again, I'd be most obliged for your help.

We had a brand new central heating system put in last month. New insulated hot water cylinder.

Plumber was around recently to bleed the rads. Since then we've noticed that a full tank of hot water will be cold in under two hours.

To test this, I put in the hot water for two hours. It was hot after two hours. Lukewarm after one and freezing (not joking) in under two.

Is this normal? I thought that if we didn't use the hot water in the morning - it'll still be there by the time we got home.

Love to hear your opinions please.

Thanks.

sullzz

Are you heating hot water by immersion , if so and switch is selected to bath it may be wired wrong .

JohnnieK

karlitob wrote: »

Hi all,

Once again, I'd be most obliged for your help.

We had a brand new central heating system put in last month. New insulated hot water cylinder.

Plumber was around recently to bleed the rads. Since then we've noticed that a full tank of hot water will be cold in under two hours.

To test this, I put in the hot water for two hours. It was hot after two hours. Lukewarm after one and freezing (not joking) in under two.

Is this normal? I thought that if we didn't use the hot water in the morning - it'll still be there by the time we got home.

Love to hear your opinions please.

Thanks.

If its a standard insulated cylinder then it wont stay at 60oC from the night before up to the time you come home from work. Also if some one runs a hot tap momentarily in the morning this will introduce cold water into the cylinder thus cooling it more.

Where is the cylinder stat located. If you imagine the cylinder as 3 thirds, the stat shoud be on the bottom third of the cylinder. If its higher then this also could be a problem.

karlitob

JohnnieK wrote: »

karlitob wrote: »

Hi all,

Once again, I'd be most obliged for your help.

We had a brand new central heating system put in last month. New insulated hot water cylinder.

Plumber was around recently to bleed the rads. Since then we've noticed that a full tank of hot water will be cold in under two hours.

To test this, I put in the hot water for two hours. It was hot after two hours. Lukewarm after one and freezing (not joking) in under two.

Is this normal? I thought that if we didn't use the hot water in the morning - it'll still be there by the time we got home.

Love to hear your opinions please.

Thanks.

If its a standard insulated cylinder then it wont stay at 60oC from the night before up to the time you come home from work. Also if some one runs a hot tap momentarily in the morning this will introduce cold water into the cylinder thus cooling it more.

Where is the cylinder stat located. If you imagine the cylinder as 3 thirds, the stat shoud be on the bottom third of the cylinder. If its higher then this also could be a problem.

Hi,

Great reply. Thanks.

The cylinder stat is on the bottom third as you suggest. I take your other points.

Can I just ask - the water in the tank is cold only two hours after its stopped heating. As you say, you wouldn't expect it to last all day but would you expect it to last longer than two hours? I can be certain but I don't think this was an issue before he bled the rads.

Lastly, (sorry to ask lots of questions) how long is enough to heat the tank to 60deg. The boiler is at 80deg and it's a standard family size cylinder. Or does the boiler turn off when the thermostat reaches its temp?

Thanks again.

JohnnieK

karlitob wrote: »

Hi,

Great reply. Thanks.

The cylinder stat is on the bottom third as you suggest. I take your other points.

Can I just ask - the water in the tank is cold only two hours after its stopped heating. As you say, you wouldn't expect it to last all day but would you expect it to last longer than two hours? I can be certain but I don't think this was an issue before he bled the rads.

Lastly, (sorry to ask lots of questions) how long is enough to heat the tank to 60deg. The boiler is at 80deg and it's a standard family size cylinder. Or does the boiler turn off when the thermostat reaches its temp?

Thanks again.

I would expect it to last a lot longer than that especially if no one was using it. Regarding heat up time it all depends on the size of the cylinder and the type of coil in it but on average for a 30x18 cylinder it should be no more than 45 mins to an hour especially if the boiler is running at that temp.

When the cylinder reaches temp the stat detects this and the boiler should shut down.
At a guess the balancing valve on the coil for the cylinder might be turned down too much and not enough flow is going through the coil to heat the water sufficiently and within the times you have allocated.

You should deffinetly contact your installer to check this out, if you open the valve too much you can unbalance the system and this could lead to problems elsewhere.

bbam

I've seen something like this before..
My bet is that a thermostat controlling a circulating pump on the heating system has been changes/moved..
This causes the pump to run on when the heating is off... it essentially drains the heat from the hot tank into the heating system.. it will dissipate the tank of hot water quite quickly..

karlitob

JohnnieK wrote: »

karlitob wrote: »

Hi,

Great reply. Thanks.

The cylinder stat is on the bottom third as you suggest. I take your other points.

Can I just ask - the water in the tank is cold only two hours after its stopped heating. As you say, you wouldn't expect it to last all day but would you expect it to last longer than two hours? I can be certain but I don't think this was an issue before he bled the rads.

Lastly, (sorry to ask lots of questions) how long is enough to heat the tank to 60deg. The boiler is at 80deg and it's a standard family size cylinder. Or does the boiler turn off when the thermostat reaches its temp?

Thanks again.

I would expect it to last a lot longer than that especially if no one was using it. Regarding heat up time it all depends on the size of the cylinder and the type of coil in it but on average for a 30x18 cylinder it should be no more than 45 mins to an hour especially if the boiler is running at that temp.

When the cylinder reaches temp the stat detects this and the boiler should shut down.
At a guess the balancing valve on the coil for the cylinder might be turned down too much and not enough flow is going through the coil to heat the water sufficiently and within the times you have allocated.

You should deffinetly contact your installer to check this out, if you open the valve too much you can unbalance the system and this could lead to problems elsewhere.

Yep, we're calling on Tuesday. Just wanted to tease it out first. Our immersion is not working well either. Had it on sink for an hour and didn't get hot. Would that tie in?

karlitob

bbam wrote: »

I've seen something like this before..
My bet is that a thermostat controlling a circulating pump on the heating system has been changes/moved..
This causes the pump to run on when the heating is off... it essentially drains the heat from the hot tank into the heating system.. it will dissipate the tank of hot water quite quickly..

Thanks for the reply. Could you explain that to me again please. Confused on these things.

kaizer13

Are you able to take and link us to a photograph showing the cylinder and its pipe connections as fitted in your set-up?
That could help us to determine a solution.

bbam

karlitob wrote: »

Thanks for the reply. Could you explain that to me again please. Confused on these things.

If your heating system continues to circulate without the heating on.
As it passes through the coil in the tank it robs the heat from your hot water in the tank.
It happens if you have a pipe stat controlling a circulating pump and the stat is set too low.

JohnnieK

karlitob wrote: »

Yep, we're calling on Tuesday. Just wanted to tease it out first. Our immersion is not working well either. Had it on sink for an hour and didn't get hot. Would that tie in?

Your immersion is separate to your initial problem.

JohnnieK

You said it's a new system! Is there zone valves on the system. A few pics would help with diagnosis. Either way it's not working right so your installer chould rectify. I still cant see how venting a few rads would cause this problem. What pressure is in the system?

karlitob

JohnnieK wrote: »

You said it's a new system! Is there zone valves on the system. A few pics would help with diagnosis. Either way it's not working right so your installer chould rectify. I still cant see how venting a few rads would cause this problem. What pressure is in the system?

Thanks for your post.

It doesnt make sense to me either. Had a shower this morning - it has a pump - water lasted for less than 5 mins. The water turned off 40 mins beforehand. I'm thinking it must be the thermostat or somehow the water isn't heating sufficiently.

Also, changed the stat in the immersion. No change. Doesnt heat it at all.

How do I check the pressure in the system?

roy rodgers

have ya searched the system for a leak?? How did the system work before the work was done?? Is the bottom half of the cylinder getting hot after 2hours of the heating been on.

freddyuk

Can you check the temperature of the water at the bottom connection of the boiler feed (the lower connection about the same level as the thermostat) when you think you have heated the cylinder? Is this pipe hot?. If it is hot then you know you do actually have a cylinder full of hot water. If you are checking at the very top of the cylinder you may only have a few gallons of hot and the rest may be cold so check that first.
Then after the heating boiler is turned off does the pump continue to run? If you can hear it running or feel it and it will be vibrating. If it is running and the boiler is off then you know there is a problem with a sensor/valve.
If it is not running and you definitely have a full cylinder of hot water then there is something else going on if that hot water dissipates in a few hours without significant usage but until we know the facts it will be difficult to speculate further.

JohnnieK

karlitob wrote: »

Thanks for your post.

It doesnt make sense to me either. Had a shower this morning - it has a pump - water lasted for less than 5 mins. The water turned off 40 mins beforehand. I'm thinking it must be the thermostat or somehow the water isn't heating sufficiently.

Also, changed the stat in the immersion. No change. Doesnt heat it at all.

How do I check the pressure in the system?

The next thing to check would be the balancing valve on the return pipe from the cylinder coil, it should be close to the cylinder, perhaps he adjusted this when he was at the rads! Try turning it anit-clockwise one turn and see if it makes a difference.

karlitob

hi everyone,

just to update you - there was a leak!!! 2 of them in fact - we just had the worst plumber ever. Thanks for all your advice.

G

shane0007

bbam wrote: »

I've seen something like this before..
My bet is that a thermostat controlling a circulating pump on the heating system has been changes/moved..
This causes the pump to run on when the heating is off... it essentially drains the heat from the hot tank into the heating system.. it will dissipate the tank of hot water quite quickly..

Definitely check out the circulating pump. See if it is still running when the boiler is off.

If not the circulating pump, turn off the cold feed to the cylinder and heat again. If it then remains hot, then you most likely have a leak on your domestic side.

shane0007

Woops, sorry did not read your last post.