back boiler

[Dave2010]

guys,

anybody know how long it would take a back boiler to heat enough water for a hot bath?

I know there maybe many variables but I'm looking at 5 hours here and it not even hot hot if you get my drift

would having the heating on make a major difference also?

as always, many thanks

 

[bigpkr]

Is say 45 mins but depends if pumped hw or gravity.

Have to checked the hw stat to see what its set at?

Also have you checked the boiler stat? If its gravity hw it will have an impact on hw temp.

 

[Hugh Jaleak]

Definately not 5 hours in normal circumstances. CH may slow things down slightly as the heated water produced by the boiler is shared with CH, but not to that extent. Depending on type of system problem could be a blockage, faulty motorised valve, or something else! Are the upstairs radiators hot?

 

[Dave2010]

hot water tank is in the loft and is from what I can tell heated by the boiler circuit, there is no heating element or thermostat on this tank.
I assume this heating is pumped up to the tank to warm it up but the produced hot water is gravity down to the bathroom which is on the ground floor

Yes all rads are hot both up and down
There is no room thermostats or anything on this system either. You basically flick the system on/off and another switch for HW or HW&CH together.

 

[Hugh Jaleak]

Sounds like you have a gravity HW/pumped CH system. The system relies on gravity to get the hot water from the boiler up to the cylinder to heat the contents.

Check the small cistern (tank) in the roof has water in it. Otherwise could be a blockage in the cylinder coil or pipes preventing circulation.

 

[Dave2010]

Sounds like you have a gravity HW/pumped CH system. The system relies on gravity to get the hot water from the boiler up to the cylinder to heat the contents.

Check the small cistern (tank) in the roof has water in it. Otherwise could be a blockage in the cylinder coil or pipes preventing circulation.

OK will check small tank. This small tank is attached to the big tank that holds the hot water if this makes any difference?

This also may sound daft but if it relies on gravity then how does the hot water get up into the loft?

 

[Hugh Jaleak]

The small tank attached to the HW cylinder is the cold storage tank, this supplies the HW tank underneath it. Usually known as a 'Fortic'. If there is no other tank present then its likely to be a 'Primatic', (might state that on manufacturers label if still present.) Primatic systems fill the boiler/CH from within the main cylinder, avoids need for seperate feed and expansion tank, vent and cold feed pipes.

I suspect there's a blockage in the pipes from boiler to cylinder. Primatic systems prevent the use of corrosion inhibitor, so good chance system is sludged up. Could try a magnet against the pipes from cylinder to boiler, if magnet sticks, thats your blockage.

Hot water is lighter (less dense) than cold water, so will rise. The heavier cold water also drops, allowing the circulation to take place around a loop of pipework. Up from boiler, into cylinder then back out and down to the boiler. Once the water in the boiler reaches the right temperature its surprising how quick (when its working properly!) the hot water goes up the flow pipe to the cylinder!

 

[Dave2010]

The small tank attached to the HW cylinder is the cold storage tank, this supplies the HW tank underneath it. Usually known as a 'Fortic'. If there is no other tank present then its likely to be a 'Primatic', (might state that on manufacturers label if still present.) Primatic systems fill the boiler/CH from within the main cylinder, avoids need for seperate feed and expansion tank, vent and cold feed pipes.

I suspect there's a blockage in the pipes from boiler to cylinder. Primatic systems prevent the use of corrosion inhibitor, so good chance system is sludged up. Could try a magnet against the pipes from cylinder to boiler, if magnet sticks, thats your blockage.

Hot water is lighter (less dense) than cold water, so will rise. The heavier cold water also drops, allowing the circulation to take place around a loop of pipework. Up from boiler, into cylinder then back out and down to the boiler. Once the water in the boiler reaches the right temperature its surprising how quick (when its working properly!) the hot water goes up the flow pipe to the cylinder!

genius!! I shall take all on board and get working it all out. Might have trouble with the magnet trick though as most the pipework is concealed but will see what happens

 

[Hugh Jaleak]

Come back if you cant, but i'd try the return (bottom pipe of the pair into the side of the cylinder) at/near the cylinder first.

Maybe that its blocked internally though, in which case you wont find it. System will have to be drained and coil flushed out.

 

[Dave2010]

hey guys,

it is a "Elson Double Fed indirect hot water tank" sticker on the side

could only do magnet trick on about 3 foot of pipe work as it is unaccessible throughout the rest. Nothing happened when I tried.

however when set to HW only both the flow and return pipes are untouchable they are so hot. When on CH&HW you can hold on to the pipe for a while (although uncomfortable)

Could this indicate a balancing problem with the heating system?

 

[Hugh Jaleak]

Ok, its an Elson, not a primatic, not had experience of an Elson, but I think the F&E is combined within the tank. Still wonder if there enough water in the system though, whilst the pipes are hot it doesnt appear to be circulating enough to heat the tank....

 

[algas]

Is there an air vent on the pipe going into the top coil connection of the cylinder, the coil could just be air locked

 

[Dave2010]

Is there an air vent on the pipe going into the top coil connection of the cylinder, the coil could just be air locked

cant see anything like that on it.

 

[Dave2010]

Ok, its an Elson, not a primatic, not had experience of an Elson, but I think the F&E is combined within the tank. Still wonder if there enough water in the system though, whilst the pipes are hot it doesnt appear to be circulating enough to heat the tank....

There is a pump under the floor boards downstairs which I believe is for the upstairs rads as once this packed in and rads did not work. Would there be another pump anywhere that may assist in the circulation?

 

[Hugh Jaleak]

Elson wont work on a pumped system from what I can tell. I think you have a simply gravity HW/pumped CH system, whereas when central heating is switched on the pump operates to move the hot water around the rads. Balancing will only affect the rads.

With the system cold (and CH off) how long do the primaries (from boiler to Elson) take to get hot? The flow (top pipe) should get hot very quickly soon after boiler begins firing as the circulation commences. With a cold tank of water i'd expect the return to be slightly cooler as the heat is transferred into the water in the tank.