Too much hot water

[73jonathan123]

Hi there, I'm hoping someone can give me advice on the following. I'm an experienced diy'er but please excuse my ignorance of the correct terminology.
I have a multi-fuel stove with a boiler in it heating my hot water. There's a hot water cylinder and a large cold water tank in the loft. My problem is that it produces so much boiling water that it vents out the cylinder into the cold water tank and I end up with very hot water coming through the cold taps and scalding hot water from the hot taps. Would installing a radiator help cool the water? If so can I just connect one to the hot pipe before it enters the cylinder? I'm in the middle of converting part of the loft so the radiator would be nearby.
Any advice much appreciated.

 

[durhamplumber]

Hi there, I'm hoping someone can give me advice on the following. I'm an experienced diy'er but please excuse my ignorance of the correct terminology.
I have a multi-fuel stove with a boiler in it heating my hot water. There's a hot water cylinder and a large cold water tank in the loft. My problem is that it produces so much boiling water that it vents out the cylinder into the cold water tank and I end up with very hot water coming through the cold taps and scalding hot water from the hot taps. Would installing a radiator help cool the water? If so can I just connect one to the hot pipe before it enters the cylinder? I'm in the middle of converting part of the loft so the radiator would be nearby.
Any advice much appreciated.

No expert but it sounds v v dangerous disaster waiting to happen

 

[muggles]

A heat leak would certainly help, but the issue you have described has killed people in the past. I suggest you get someone familiar with these systems to come and take a look, to advise you on what needs to be done to correct it

 

[DP]

I'm an experienced diy'er but please excuse my ignorance of the correct terminology.

Your experience has certainly highlighted an issue that is potentially dangerous on several fronts. It is a situation that needs to be rectified not like yesterday but last week

If that storage vessel fails, very hot water will be everywhere, hopefully no one will be under the flood at that moment.

 

[73jonathan123]

Thanks for the responses I'm posting this reply from the garden . Is the danger that the hot water causes the cold water tank to collapse?
If I can give a more detailed description hopefully the situation might not seem so dire. So the boiler (I think they're called 50/50 boilers)was installed about 10 years ago and heats the cylinder in the loft about 3m above. The cylinder has the U bend pipe on top to release pressure and steam into the cold water tank. The cold water tank has supporting aluminium bars around it and I've never noticed it looking warped or stretched in any way. The cold tank feeds a toilet and sink in a w.c and the rest of the house is on mains water. After 4-5 hours with the stove on the hot water builds up in the cylinder and with the surge of hot water from the boiler there's a spurt of hot water into the cold tank. Over time this heats the cold water. There's an overflow out of the roof to the gutter to prevent the cold tank overfilling. Running baths and using the toilet and sink in the w.c cools it back down. I'm thinking that integrating a radiator would help cool the water circulating in the system and stop so much excess hot water being produced but I'm not sure at what point in the system one should be installed or if it is worth it or is it safe?
Thanks, Jonny.

 

[Madrab]

Has it always done this or is this a new occurrence? In effect you have an uncontrolled heat source heating your hot water and you need it setup properly to ensure that the heat to your cylinder can be controlled. There would usually be a heat leak though a rad that can't be closed down and also a safety temp or temp/pressure relief valve attached to the cylinder.

As suggested you need to get a professional in as your current situation isn't safe. Also if you are getting that temp of hot water from the cylinder then you must fit a TMV/Blending valve on the HW supply from the cylinder to allow the temp at the outlets to be regulated to a safe temp.

 

[73jonathan123]

Thanks Madrab. It's been like this since the day it was fitted around 10yrs ago. I've tolerated the excessively hot water but I'm converting part of the loft and thought it would be a good time to put a radiator in. A plumber actually told me at one point that installing a radiator might cool the water too much.
I've a couple of questions if that's ok? Is the open pipe on top of the cylinder venting into the cold tank acting as a pressure relief valve and is this adequate? The end of this pipe is open, it sits through the lid above the surface of the cold water. Where in the system should a heat leak radiator be installed?
Many thanks, Jonny.

 

[Madrab]

The open vent on the cylinder is doing what it's supposed to and keeping the pressure it the cylinder down but you don't want excessive venting, it's just a waste. You need to strike a balance between the hot water getting hot enough and then balance that system temperature using a heat soak.

Again that is where an engineer experienced in these types of system would be advised as he should be able to balance the system properly and check you have the safety features needed installed.

 

[JimCrow]

Is this stove solely for hot water?, could you post a pic of your hot water cylinder including the side tappings?.

 

[73jonathan123]

Yep, the stove was initially for heating only and I had an immersion heater heating the water then I got the back boiler fitted to heat the water. I'll post some pics.
Thanks.

 

[73jonathan123]

With regards to the system being dangerous. What sounds so dodgy about it? Is it the potential for the cold tank to collapse due to the hot water? The tank is very robust with aluminium bars around the sides. The hot cylinder has an open pipe coming from the top which vents steam and hot water, it's not pressurised and it's been operating for 10yrs so far. The water from the hot tap is scalding hot but I'm always conscious of that.
Thanks, Jonny.

 

[durhamplumber]

The hot cylinder has an open pipe coming from the top which vents steam

That bit...steam will sharp weaken ally and result in a bath full of scalding water killing someone.

 

[73jonathan123]

Sorry I'm probably not describing the system accurately. It was probably designed on the back of a fag packet. This pipe goes from the top of the cylinder through the top lid if the cold tank and sits above the surface of the water. In time when the hot water builds up in the system the back boiler sends a surge of hot water up to the cylinder, when this happens a spurt of steam and hot water falls into the cold water. The aluminium bars are around the outside of the tank to support the sides.
Thanks, Jonny.

 

[73jonathan123]

side, bottom top side,top

 

[JimCrow]

Thats a direct cylinder you have, you SHOULD have a copper boiler fitted in the stove, the heat leak would need to be a non ferrous ( brass towel warmer type) and not a standard radiator.