Backboiler - no gravity circuit!

tipperary

All

Our house was built a couple of years ago - it is an 'upside down' design, with the living quarters upstairs, and bedrooms downstairs. The hot press is also located downstairs.

In the living room we have a stove with a back boiler (Hunter Herald 14). The pipework includes a stat which turns on the pump at the required temp (after a little bit of banging noise). From recent research it seems that this type of installation is a big no-no due to the risks should the pump break/power cut.

I would like to make the system as safe as possible, while still maintaining the back boiler (wife insists on having a fire for six months of the year!). I am trying to figure out what my options are. So far, the possibilities I have come up with are:
1. change stove to non-boiler model - don't want to do this. Wife won't let me do this.
2. add a second cylinder (probably in the attic) which would have gravity circuit to the stove. Use pump to transfer heat from this cylinder to the main hot water cylinder and rads.
3. Use some type of Uninterruptable Power Supply unit to ensure power is available to the pump even in the event of a power cut (doesn't help if pump breaks).

Any other options, or further info on adding a second cyliner (or simialar) would be appreciated.

Stove Fan

tipperary wrote: »

All

Our house was built a couple of years ago - it is an 'upside down' design, with the living quarters upstairs, and bedrooms downstairs. The hot press is also located downstairs.

In the living room we have a stove with a back boiler (Hunter Herald 14). The pipework includes a stat which turns on the pump at the required temp (after a little bit of banging noise). From recent research it seems that this type of installation is a big no-no due to the risks should the pump break/power cut.

I would like to make the system as safe as possible, while still maintaining the back boiler (wife insists on having a fire for six months of the year!). I am trying to figure out what my options are. So far, the possibilities I have come up with are:
1. change stove to non-boiler model - don't want to do this. Wife won't let me do this.
2. add a second cylinder (probably in the attic) which would have gravity circuit to the stove. Use pump to transfer heat from this cylinder to the main hot water cylinder and rads.
3. Use some type of Uninterruptable Power Supply unit to ensure power is available to the pump even in the event of a power cut (doesn't help if pump breaks).

Any other options, or further info on adding a second cyliner (or simialar) would be appreciated.

Personally I would just install a large heat leak radiator plumbed in near the stove teeing off the rear of the stoves piping. Either installed behind in another room etc or to the side that works on gravity. This should be plumbed in 3/4 copper piping. This would need to be a 4 tapping rad and the top tapping used as flow. This rad all installed with lockshield valves. ie permanently set open. Ie no TRV/manual valve.
Something sized like a 600 by 1400 double if you have room.
This would help dissipate the heat from the boiler stove in event of a powercut. If your hunter has the optional boiler thermostat it should close the air supply automatically as there wouldn't be as much demand/heat needed. If your stove hasn't got the optional boiler thermostat then in a powercut you would need to close the air inlet vents yourself to slumber the fire more. Banging is the water boiling in the stoves boiler and isn't normal.

I would certainly get someone in to install a heat leak radiator and check the feed and vent pipe and boiler system for safety and for now ideally don't light the fire:(. A boiler stove certainly needs a gravity heat leak radiator and a seperate cold feed and vent pipe.
You could turn the pipe thermostat down as well so the pump switches on earlier if you really need the fire going in this warm weather but could boil the water inside in the event of a powercut:eek:. A stove overheating apparantly isn't nice to see!!

Stove Fan:)

tipperary

Stove Fan wrote: »

Personally I would just install a large heat leak radiator plumbed in near the stove teeing off the rear of the stoves piping. Either installed behind in another room etc or to the side that works on gravity. This should be plumbed in 3/4 copper piping. This would need to be a 4 tapping rad and the top tapping used as flow. This rad all installed with lockshield valves. ie permanently set open. Ie no TRV/manual valve.
Something sized like a 600 by 1400 double if you have room.
This would help dissipate the heat from the boiler stove in event of a powercut. If your hunter has the optional boiler thermostat it should close the air supply automatically as there wouldn't be as much demand/heat needed. If your stove hasn't got the optional boiler thermostat then in a powercut you would need to close the air inlet vents yourself to slumber the fire more. Banging is the water boiling in the stoves boiler and isn't normal.

I would certainly get someone in to install a heat leak radiator and check the feed and vent pipe and boiler system for safety and for now ideally don't light the fire:(. A boiler stove certainly needs a gravity heat leak radiator and a seperate cold feed and vent pipe.
You could turn the pipe thermostat down as well so the pump switches on earlier if you really need the fire going in this warm weather but could boil the water inside in the event of a powercut:eek:. A stove overheating apparantly isn't nice to see!!

Stove Fan:)

Hi Stove Fan

thanks for your input. I found the sticky on stoves after posting - a treasure trove of essential information - mostly from your good self!

Anyway, the layout of the house doesn't really lend itself to adding another rad - beside the stove is a door at one side, and a wall with a window on the other. The top of the stove is above the bottom of the window so won't be able to gravity feed a rad under the window.

I think the best solution is probably to put the heat leak radiator in the attic. I know this will waste heat from the back boiler, but I hope that if I plumb the heat leak rad (and feed/expansion) on a tee of the pumped line, then when the pump is operating that the hot water will mostly stay in the pumped line rather than going up to the heat leak radiator. Another option I considered would be to have a three port zone valve that would default to allowing water up to the heat leak rad, but when the pipe stat signals the pump to come on, would also actuate the zone valve. The problem with this I guess is that the temps might be too hot for the zone valve, melt the innards of it, and block the whole thing!

tipperary

I have one other query on this.

The theory for the heat leak radiator states that the connection into the heat leak radiator is constantly rising, to allow the hot water to rise by convection. However, a lot of the guidance I have seen (e.g. http://www.ecoangus.ie/ecoangus_images/Test_Reports_and_Instruction%20Manuals/Hetas_Engineers_Training_Manual.pdf) suggests that the branch from the vertical pipe to the heat leak radiator should be falling, so as to ensure that any air in the heat leak rad can vent automatically. This will stop air locks

What way have people here dealt with this issue?

pache

tipperary wrote: »

All

Our house was built a couple of years ago - it is an 'upside down' design, with the living quarters upstairs, and bedrooms downstairs. The hot press is also located downstairs.

In the living room we have a stove with a back boiler (Hunter Herald 14). The pipework includes a stat which turns on the pump at the required temp (after a little bit of banging noise). From recent research it seems that this type of installation is a big no-no due to the risks should the pump break/power cut.

I would like to make the system as safe as possible, while still maintaining the back boiler (wife insists on having a fire for six months of the year!). I am trying to figure out what my options are. So far, the possibilities I have come up with are:
1. change stove to non-boiler model - don't want to do this. Wife won't let me do this.
2. add a second cylinder (probably in the attic) which would have gravity circuit to the stove. Use pump to transfer heat from this cylinder to the main hot water cylinder and rads.
3. Use some type of Uninterruptable Power Supply unit to ensure power is available to the pump even in the event of a power cut (doesn't help if pump breaks).

Any other options, or further info on adding a second cyliner (or simialar) would be appreciated.

New wife maybe!!.....anyone...anyone..:rolleyes:

Stove Fan

tipperary wrote: »

Hi Stove Fan

thanks for your input. I found the sticky on stoves after posting - a treasure trove of essential information - mostly from your good self!

Anyway, the layout of the house doesn't really lend itself to adding another rad - beside the stove is a door at one side, and a wall with a window on the other. The top of the stove is above the bottom of the window so won't be able to gravity feed a rad under the window.

I think the best solution is probably to put the heat leak radiator in the attic. I know this will waste heat from the back boiler, but I hope that if I plumb the heat leak rad (and feed/expansion) on a tee of the pumped line, then when the pump is operating that the hot water will mostly stay in the pumped line rather than going up to the heat leak radiator. Another option I considered would be to have a three port zone valve that would default to allowing water up to the heat leak rad, but when the pipe stat signals the pump to come on, would also actuate the zone valve. The problem with this I guess is that the temps might be too hot for the zone valve, melt the innards of it, and block the whole thing!

How about fitting the heat leak rad on the other side of the wall where the door is. Ie drill two holes through the wall to the room on the other side?

The heat leak rad doesn't have to be in the same room as the stove providing the pipework from the stoves flow can rise slightly to the top of the rad inlet.The flow would T off from the stoves top, flow outlet.
This if possible would be much better as your getting the heat:) You would risk the radiator in the loft freezing and bursting when fire wasn't lit unless you used heating grade antifreeze in the system.

With regards to what hetas said to do with air trapped I always have the gravity flow pipe rising to the radiators top inlet and return opposite bottom but slightly sloping back to stove.
There shouldn't be any air trapped as during filling with water you vent the heat leak rad anyway, like all the others. I then bleed all rads a few weeks after refilling.

There should be no air locks form if the system is installed correctly:).

I personally would get a visit by a plumber and evaluate the layout and see what can be done. I personally wouldn't really want a rad in the loft, unless a proper insulated room.

Stove Fan:)

tipperary

Stove Fan wrote: »

This if possible would be much better as your getting the heat:) You would risk the radiator in the loft freezing and bursting when fire wasn't lit unless you used heating grade antifreeze in the system.

Stove Fan:)

Hi, thanks again Stove Fan. I had just thought about the whole radiator freezing aspect late last night. Guess I'll just have to fit the rad in either the living room, or the bedroom behind somehow.

I pulled off a few panels last night and realised the original plumber had fitted a pressure release valve. I guess the installation wasn't quite as bad as I first thought, but I will still rest easier with the heat leak rad fitted.

Stove Fan

tipperary wrote: »

Hi, thanks again Stove Fan. I had just thought about the whole radiator freezing aspect late last night. Guess I'll just have to fit the rad in either the living room, or the bedroom behind somehow.

I pulled off a few panels last night and realised the original plumber had fitted a pressure release valve. I guess the installation wasn't quite as bad as I first thought, but I will still rest easier with the heat leak rad fitted.

Make sure this pressure release valve is piped to the outside and not just the valve only as if it discharges it would flood the house:eek: I have seen quite a few fitted behind stoves/fireplaces but not discharged to outside/internal drain.

In the living/bedroom will be fine for the rad:)

Stove Fan:)

jj58

is there any way you can put steel tank 100 liter of more above stove for gravity, when that heat to 65 deg it wil;l bring on pump and pump it to rads and cylinder,
just like oil boiler sort of thing,
i had do something like that before, worked well i must say

tipperary

jj58 wrote: »

is there any way you can put steel tank 100 liter of more above stove for gravity, when that heat to 65 deg it wil;l bring on pump and pump it to rads and cylinder,
just like oil boiler sort of thing,
i had do something like that before, worked well i must say

Hi. Something like that was my first plan, but I think the problem is that if the stove is on, the cylinder will be at 65 deg. If there is a power cut, there is very little capacity for the cylinder to absorb more heat. This is the reason why heat leak rads are recommended even where there is a gravity circuit to the cylinder.

On a related matter, there is no cold feed from the expansion tank so I need to add this. Can the oil boiler and back boiler share a common feed and expansion tank, with each system having it's own feed and expansion pipes?

jj58

well if u can bring the only feed to the steel tank and an expansion off that, thats all u need

on standard solid fuel and oil link up. one feed into the return off the solid fuel line, it will feed the oil boiler through an unvalved/unrestricted return and one expansion on the highest point of the solid fuel line

insu1

It can end up way worse than you'd think if its not safe by design. If it goes well above boiling point ,it might decide to turn to steam if it loses pressure

The little valve probably wouldn't be able to vent the amount of steam generated so it'd might take the next easiest route and burst the boiler at the back of the fire -


kind of related :

http://www.youtube.com/watch?v=G4cscaFyItA

Old steam boiler stuff :


"We all know that when water boils and becomes steam, it increases in volume 1700 times and this sudden and massive release of steam from water is as destructive as dynamite.
Rolla Carpenter in his classic 1895 book, Heating and Ventilating Buildings, tells how a Cornish cylinder boiler under 30 psig has the ability to leave a basement (steam explosion) with an initial velocity of 290 miles per hour and rise to a height of 3,431 feet!........

The first low water cutoffs were introduced in 1923 and they weren't very effective with coal-fired boilers."


- http://hvacwebtech.com/steamboilers.htm


again just vaguely related but possible ? :

http://www.hse.gov.uk/press/2009/coisw61109.htm

*Attached photo is graphic

hondatrx

We have just installed a back boiler stove with a 2 cyclinder tank...its heating the rads not problem but then it pitches to the attic when the pump is switched on. why would this be happening?

Dtp79

insu1 wrote: »

It can end up way worse than you'd think if its not safe by design. If it goes well above boiling point ,it might decide to turn to steam if it loses pressure

The little valve probably wouldn't be able to vent the amount of steam generated so it'd might take the next easiest route and burst the boiler at the back of the fire -


kind of related :

http://www.youtube.com/watch?v=G4cscaFyItA

Old steam boiler stuff :


"We all know that when water boils and becomes steam, it increases in volume 1700 times and this sudden and massive release of steam from water is as destructive as dynamite.
Rolla Carpenter in his classic 1895 book, Heating and Ventilating Buildings, tells how a Cornish cylinder boiler under 30 psig has the ability to leave a basement (steam explosion) with an initial velocity of 290 miles per hour and rise to a height of 3,431 feet!........

The first low water cutoffs were introduced in 1923 and they weren't very effective with coal-fired boilers."


- http://hvacwebtech.com/steamboilers.htm


again just vaguely related but possible ? :

http://www.hse.gov.uk/press/2009/coisw61109.htm

*Attached photo is graphic

Ah jaysus I was havin my dinner when I opened that pic!!