Back boiler by-pass?

Danpad

I have a question that's been bugging me for ages. We have a back boiler, which, when we light the fire and turn the pump on, heats the rads and water with great efficiency. It lets us know when it needs to be turned on with lots of knocking and clanging noises! My question is: If there was a power cut and we couldn't turn the pump on what would happen? Would it explode?!! So, in such an event, is there a way of by-passing the boiler when lighting the fire? I'm thinking along the lines of an insert or something that would vent the heat straight up the chimney...or am I asking the impossible?

LIFFY FISHING

The pump you refere to is actually not a pump, its a circulator for moving the hot water around the house, if the pump wasnt on the water would free vent, the knocking you hear from your pump is just resistance, nothing would happen if your electrics go off, worst case is the system will pitch back into your expansion tank.

LIFFY FISHING

The pump you refere to is actually not a pump, its a circulator for moving the hot water around the house, if the pump wasnt on the water would free vent, the knocking you hear from your pump is just resistance, nothing would happen if your electrics go off, worst case is the system will pitch back into your expansion tank.

TPM

Danpad wrote: »

I have a question that's been bugging me for ages. We have a back boiler, which, when we light the fire and turn the pump on, heats the rads and water with great efficiency. It lets us know when it needs to be turned on with lots of knocking and clanging noises! My question is: If there was a power cut and we couldn't turn the pump on what would happen? Would it explode?!! So, in such an event, is there a way of by-passing the boiler when lighting the fire? I'm thinking along the lines of an insert or something that would vent the heat straight up the chimney...or am I asking the impossible?

It is quite possible that it could explode, The knocking and clanging you are hearing could be the water boiling in the boiler!!!!

It is not possible to know or even make assumptions about how safe your system is with out seeing it.

Solid fuel boilers are potentially deadly if not correctly installed.

If you have any doubts or concerns you should get it checked out by someone who knows solid fuel systems

shane0007

TPM wrote: »

It is quite possible that it could explode, The knocking and clanging you are hearing could be the water boiling in the boiler!!!!

It is not possible to know or even make assumptions about how safe your system is with out seeing it.

Solid fuel boilers are potentially deadly if not correctly installed.

If you have any doubts or concerns you should get it checked out by someone who knows solid fuel systems

Absolutely agree. And if nothing else, the banging sends shock waves through your heating pipes that can affect the integrity of joints. The banging is heat building up within the back boiler and boiling.
It is like leaving a kettle on full boil continuously jamming the switch on. Even though it has a spout open to atmosphere, you would not stand beside it. By boiling you are converting the water to steam and 1 litre of water converts to 1,600 litres of steam. If for some reason the vent blocked with crap or the like, what would the outcome be with that volume trying to release?

Danpad

Thanks very much for the responses. The system actually works perfectly. When we light the fire we don't even wait anymore for the noises, we simply turn the pump (circulator) on and we have lovely hot rads and water. So, in the event of a power cut and we're unable to turn the pump on I guess we shouldn't light the fire. In the abscence of an insert that could block the heat from the fire away from the back boiler but still guide the smoke up the chimney, I suppose I'll just have to rely on a good old super ser.
Thanks again.

demanufactured

Danpad wrote: »

Thanks very much for the responses. The system actually works perfectly. When we light the fire we don't even wait anymore for the noises, we simply turn the pump (circulator) on and we have lovely hot rads and water. So, in the event of a power cut and we're unable to turn the pump on I guess we shouldn't light the fire. In the abscence of an insert that could block the heat from the fire away from the back boiler but still guide the smoke up the chimney, I suppose I'll just have to rely on a good old super ser.
Thanks again.

Have a look at your heating system....follow the pipes to see where everything goes.

You should have a small tank in your attic which is the feed and expansion tank for your system.
If your system is not pressurised ( it shouldn't be anyway) ..then all that would happen in the event of a power cut I'd your upstairs rads ( assuming its a two story) and hot water would get heated only.
Any excess heated water would get pushed up into the expansion tank.

Take a picture of your back boiler and a few pics of the pipework and post them here if you like.

shane0007

demanufactured wrote: »

..then all that would happen in the event of a power cut I'd your upstairs rads ( assuming its a two story) and hot water would get heated only.

Not quite. The reason for the banging is that there is no proper gravity circuit to the coil in the DHW cylinder, hence the banging!

wilson10

Get someone to look at you system sooner rather than too late.

I'm not a plumber but I just installed a back boiler myself and can't believe how efficient it actually is and how much energy I've wasted over the years, it heats the hot water and warms 16 rads reasonably well, while throwing out a fair amount of heat into the room.

I can't understand how someone is running a system having to remember to switch on a pump, for the sake of a 15 euro pipe stat.

I have a thermostatic switch clamped to my return pipe from my copper cylinder which switches on the pump when it reaches about 40 degrees, a simple cheap job which could avert a disaster.

Get it seen to for peace of mind.

shane0007

wilson10 wrote: »

I have a thermostatic switch clamped to my return pipe from my copper cylinder which switches on the pump when it reaches about 40 degrees, a simple cheap job which could avert a disaster.

The pipe stat should be on the flow pipe as close to the stove as possible! Not on the return from the cylinder.

Danpad

Folks, I really appreciate the input. I'd like to clarify the situation though. Our system works perfectly. When we light the fire and turn the pump on the rads and hot water are heated. What i'm saying is : If we were unable to turn the pump on, say due to a power cut then it would start complaining. In the even of that hypothetical (but not far fetched) situation occuring - is there an insert (or something) we could use which would allow us to still light a fire but keep the heat away from the back boiler? Please understand it's I'm ignorant when it comes to all things plumbing etc. Maybe I'm talking utter rubbish and the only workaround is to install a stove?

wilson10

shane0007 wrote: »

The pipe stat should be on the flow pipe as close to the stove as possible! Not on the return from the cylinder.

It's interesting you say that as there was a bit of contraversy over where it should go.

I was advised to put it on the return as if I put it on the flow pipe the pump would come on too early and never allow the cylinder coil to heat.

I'm using the 4 tappings on the back boiler, making 2 seperate circuits. one diagonally top to bottom of the boiler to the copper cylinder and the other diagonally top to bottom of the boiler to the rads using the circulator pump.

The cylinder heats by gravity circulation, hot water rising, no pump.

When this system has done some work and the return starts to heat up to about 40, the pump, located on the return of the other circuit kicks in and takes practically all the hot water for the rads.

I spent the first few nights nervously listening to the boiler, feeling pipes, ready to overide the switch, but a small bit of tweaking and the system seems to work very well.

shane0007

Danpad wrote: »

Folks, I really appreciate the input. I'd like to clarify the situation though. Our system works perfectly. When we light the fire and turn the pump on the rads and hot water are heated. What i'm saying is : If we were unable to turn the pump on, say due to a power cut then it would start complaining. In the even of that hypothetical (but not far fetched) situation occuring - is there an insert (or something) we could use which would allow us to still light a fire but keep the heat away from the back boiler? Please understand it's I'm ignorant when it comes to all things plumbing etc. Maybe I'm talking utter rubbish and the only workaround is to install a stove?

There is no such "insert". The heat must be dissipated via an unrestricted gravity circuit to and from the dhw cylinder in 1" pipework with a maximum length of approx 27ft, taking away 500mm for each 90 elbows and 300mm for each sweeping bend. Without that it is dangerous if there was a power cut or if the pump fails. It should also have its own coil in the cylinder.

shane0007

wilson10 wrote: »

It's interesting you say that as there was a bit of contraversy over where it should go.

I was advised to put it on the return as if I put it on the flow pipe the pump would come on too early and never allow the cylinder coil to heat.

I'm using the 4 tappings on the back boiler, making 2 seperate circuits. one diagonally top to bottom of the boiler to the copper cylinder and the other diagonally top to bottom of the boiler to the rads using the circulator pump.

The cylinder heats by gravity circulation, hot water rising, no pump.

When this system has done some work and the return starts to heat up to about 40, the pump, located on the return of the other circuit kicks in and takes practically all the hot water for the rads.

I spent the first few nights nervously listening to the boiler, feeling pipes, ready to overide the switch, but a small bit of tweaking and the system seems to work very well.

It sounds like it is piped well. The stat should be in the flow out of the back boiler going to the cylinder, generally set to above 50c. Above 55 and no legionaries will survive.
If you we're sorrows about dumping heat out of the cylinder you could use 2 pipe stats wired in series. One turn on above a certain temp and the other turning off below a given temp. Not needed though. If you have a continuous rise from the flow to the cylinder in unrestricted 1" copper within the permissible length, you will have no issues.

wilson10

shane0007 wrote: »

It sounds like it is piped well. The stat should be in the flow out of the back boiler going to the cylinder, generally set to above 50c. Above 55 and no legionaries will survive.
If you we're sorrows about dumping heat out of the cylinder you could use 2 pipe stats wired in series. One turn on above a certain temp and the other turning off below a given temp. Not needed though. If you have a continuous rise from the flow to the cylinder in unrestricted 1" copper within the permissible length, you will have no issues.

My cylinder is a single coil so the back boiler and oil boiler are teed together which is probably not the most efficient way of doing it and I think does cause strange side effects in certain circumstances, with water deciding to flow in an unintended direction.

I'm considering investing in a twin coil cylinder which will split the 2 systems.

Do you think this would be a good idea or is it common for a single coil to share the 2 heat generating systems.

shane0007

wilson10 wrote: »

I'm considering investing in a twin coil cylinder which will split the 2 systems.

Do you think this would be a good idea or is it common for a single coil to share the 2 heat generating systems.

It is a must!

TPM

Danpad wrote: »

Our system works perfectly.

In your first post you confirmed that your system is not working perfectly

Danpad wrote: »

We have a back boiler, which, when we light the fire and turn the pump on, heats the rads and water with great efficiency. It lets us know when it needs to be turned on with lots of knocking and clanging noises!

It may be heating the water and rads but the main design function of solid fuel boilers is that they must be capable of dissipating enough heat through thermosyphon (circulation of the heating water with out the aid of a circulating pump) through a dedicated coil in the hot water cylinder and an additional radiator if necessary.
you would not be hearing the knocking and clanging If it was perfect
This aspect of solid fuel systems is frequently over looked.

Below shane points out the basic pipework requirements in the primary circuit and this must be installed so that it allows thermosyphon.

shane0007 wrote: »

The heat must be dissipated via an unrestricted gravity circuit to and from the dhw cylinder in 1" pipework with a maximum length of approx 27ft, taking away 500mm for each 90 elbows and 300mm for each sweeping bend. Without that it is dangerous if there was a power cut or if the pump fails. It should also have its own coil in the cylinder.

Soild fuel boilers can be dangerous and alot of people including plumbers are not aware of the implications of the systems, and Information on the correct installation of these systems is not easy to find.

I dont mean to come across as aggressive or knowing it all(far from it) but I cant stress enough how important it is to have solid fuel systems installed correctly and how many are not. Its just one thing that rubs me up the wrong way

shane0007

Very well put.

Danpad

Thanks lads. Before we call in a plumber and potentially spend money that we can ill afford I'd just like to be crystal clear about our situation. We have a bog standard open fireplace with a back boiler. (The house is about 25 yrs old.) We light the fire, after about an hour when the fire's built up we flip a switch on the wall and it turns a pump/circulator on and all the rads and water are heated. If we forget to switch the pump on, it (the boiler?) wil begin to make noises for the three seconds it takes us to cross the room and hit the switch. This has never alarmed us. My concern is that if we have the fire lit one day and, for example, there's a power cut before we turn the pump on, what could happen? If the general consensus is that the boiler should NOT, EVER make any noise and what we do hear once in a blue moon (when for example, we're not in the room at the exact time the boiler has hit the required temp for the pump to be turned on) is a clear indication that something is badly wrong then I guess we need to get it looked at - if this IS the case then the few neighbours I spoke to yesterday are in the same boat as they hear the same noises every now and again if they fail to switch the pump on for a few seconds. One of these neighbours, an elderly gent has lived in his house pretty much since it was built and said it had never been any different. He then said: "of course the bloody thing is going to give out if you don't turn it on" and threatened to get his cricket bat and give me a hiding if I didn't cop myself on :-)

DoneDL

The likelyhood is that the same plumber installed the solid fuel on all those properties. As has been mentioned in previous post the system is not safe. Is the cylinder dual coil?

beazee

DoneDL wrote: »

Is the cylinder dual coil?

it's not:

wilson10 wrote: »

My cylinder is a single coil so the back boiler and oil boiler are teed together

DoneDL

beazee wrote: »

it's not:

I was replying to the OP who hasn`t mentioned their cylinder.

beazee

My bad, thought this was the very same poster.
Need to focus more on who's writing what.

Danpad

Thanks for all the advice. We're not concerned about the noise we sometimes hear prior to turning the pump on. What I was asking was whether or not there was some kind of insert we could use in the fireplace that would take heat away from the boiler thus negating the need to switch it on or averting any problem if there was a power cut and we couldn't turn the pump on whilst a fire is lit. This was answered - there is no such insert. The noise issue, although it only lasts for perhaps three seconds, has inadvertently become the main focus of this thread but as some of you have indicated that it's a problem I'm going to ring a plumber and seek his input (for free, if he will, over the phone). I'll let you know what he tells me.
Cheers.

Danpad

So, eventually got hold of a plumber who, albeit briefly, gave me his view:

Me: "I have a back boiler that sometimes makes a bit of noise when the fire is lit and we don't turn the pump on."
Him:"OK, well does it stop when you turn the pump on?"
Me:"Yes."
Him:"When did you have it installed?"
Me:"We didn't, it was there when we moved in. The house is 20-25 years old. I have no idea about heating systems."
Him:"Well, in laymans terms, it's a boiler, served by a pump, if you don't turn the pump on the water's going to keep on boiling putting enormous pressure not only on the boiler but the attached pipework, the pump, seals, joints, valves etc. In fact the whole system could be stressed."
Me:"We do turn the pump on, pretty much as soon as we hear the boiler begin to give out. Then the noise disappears every time."
Him: "Your pump is working then, however your boiler is old and you should get it looked at and at least serviced."
Me:"Do I need to be concerned about my boiler exploding?"
Him:"Well, like I said, it's going to generate some noise at certain temperatures. Always make sure you turn the pump on before it gets to that stage but get the boiler looked at and seviced anyway to pre-empt any issues and determine whether or not it has been compromised."

TPM

Sorry to sound like a broken record

The noise is not good and should not be happening.

It may stop when you turn on the pump.

What happens if the day comes you cant turn on the pump? like there is a power cut or the pump fails, ant btw if the power goes or the pump fails after you had turned it on it is the same difference.

There is no device to prevent the heat from a solid fuel fire reaching the boiler, This is why it is essential that these systems are done properly.

I know alot if not the majority of old solid fuel systems bang and boil if the pump is not switched on, this does not make it right, it is only a matter of time before someones luck runs out and one of these systems fail dramatically.

I have said it before I will say it one more time and I will leave at that

SOLID FUEL BOILERS SHOULD NOT BANG,KNOCK OR CLANG EVER!!!!!!
TURNING ON A PUMP BY A SWITCH OR A PIPE STAT DOES NOT MAKE IT RIGHT IT IS STILL DANGEROUS AND POTENTIALLY LEATHAL

I am going to leave it at that now, the record player is turned off:p

Daisy M

Ok not an expert by any means but have the same set up as you op. We were told to leave the circulation pump on all the time which is what we do. We set the stat in the hot press at around 40 which means that once water in the tank is at 40 anything after that will go to the rads. Hence we have no banging if I set the stat at the highest level, around 80/85 then a banging noise would start when the tank gets really hot. Have you checked your hotpress for a stat?

Now to answer your question if there was a power cut and your water was still working at the mains all you need to do is turn on your hot tap and let the water run out and be replaced by cold water. This is usually not an option for us as when electricity goes usually the pumphouse on our group scheme loses power too and we lose supply, but on the couple of occasions that we continue to have mains water I have been able to have open fire on and I run the tap before the tank gets too hot.

shane0007

Daisy M wrote: »

Ok not an expert by any means but have the same set up as you op. We were told to leave the circulation pump on all the time which is what we do. We set the stat in the hot press at around 40 which means that once water in the tank is at 40 anything after that will go to the rads. Hence we have no banging if I set the stat at the highest level, around 80/85 then a banging noise would start when the tank gets really hot. Have you checked your hotpress for a stat?

Now to answer your question if there was a power cut and your water was still working at the mains all you need to do is turn on your hot tap and let the water run out and be replaced by cold water. This is usually not an option for us as when electricity goes usually the pumphouse on our group scheme loses power too and we lose supply, but on the couple of occasions that we continue to have mains water I have been able to have open fire on and I run the tap before the tank gets too hot.

That only applies if you have a true gravity circuit to the cylinder.

Daisy M

shane0007 wrote: »

That only applies if you have a true gravity circuit to the cylinder.

Pardon my ignorance:) but which only applies, leaving the circulation pump on all the time is it? How does a novice go about knowing if they have a true gravity circuit to the cylinder?

shane0007

You are only leaving the power supply in to the pump which is in turn wired through the pipe stat you mentioned in the hot press. This in fact should be on the flow pipe from the back boiler.
A novice would probably not be able to recognise whether or not they have a true gravity circuit. The pump should be on the secondary circuit to the rads.

Vivi13

I've just moved into a new house.

We were told its oil fired central heating and an immersion switch if we wanted hot water only (for bathing kids etc during summer). We were away all this week, so the heating wasn't switched on, we are home tonight and lit the fire only and found the water in the tap to be hot now.

Could there be a back boiler and if there is can anyone give us advice on what to do next to use the hot water for radiators. There are no switches next to the fireplace and no exposed pipes, however, on inspection of the area the wall to the left of the fireplace is warm. About the thickness of a pipe.

Any ideas/suggestions?