Dual Heating-Gas/solid fuel query

Widescreen

Folks

We bought a house several years ago and when buying it the guy mentioned something about the back boiler not being in use anymore as they had got gas installed about 5 years previously. As we had no intention of using the fireplace ,and seven years have slipped by it has slipped my mind what exactly he said about using the fire and the gas heating at the same time.

I actually rang the guy who sold us the house and he was not even 100% sure himself what way the system worked for sure.

Basically my question is how do i establish if it is possible/safe to light a fire. Is there something I can look for which may confirm this? I have a feeling the back boiler may have been "disconnected" when the gas heating was installed for some reason.

any help/hints appreciated

DoneDL

Is the cylinder dual coil or a single coil.

heinbloed

Make sure there is no 'live' gas pipe in the open fire place installed.

Widescreen

DoneDL wrote: »

Is the cylinder dual coil or a single coil.

i assume you mean the copper cylinder in hot press? how would I check that?

Widescreen

heinbloed wrote: »

Make sure there is no 'live' gas pipe in the open fire place installed.[/QUOTE

Would that be under the back boiler? what sort of piping would it be do you think?

thanks

heinbloed

Get a gas fitter in to check the gas distribution system, he will give his o.k. to your plans in writing.
Gas pipes could be burried anywhere. Most likely in the vicinity of a combustion place.
Check the chimney for pipes and cables, unused chimneys are frequently used as ducting channels.

Widescreen

heinbloed wrote: »

Get a gas fitter in to check the gas distribution system, he will give his o.k. to your plans in writing.
Gas pipes could be burried anywhere. Most likely in the vicinity of a combustion place.
Check the chimney for pipes and cables, unused chimneys are frequently used as ducting channels.

Due to get the boiler serviced , so will do as you say, many thanks for that feedback.

S Connor

Hi guys. Can anyone please help me with something as I'm really scared it's dangerous. I have recently had a grant triple pass back boiler fitted and I already had gas heating. The gas heating has been installed at least 8 years with no problems. My problem now is that when we light the fire both of the water pipes connected to my gas boiler are heating up, a lot!!! There is a non return valve fitted and even that is roasting hot. Surely this isn't right??? One pipe is slighter hotter then the other which leaves me to believe that the hot water is going in through the gas boiler through one pipe, cooling slightly and coming out the other pipe. Of course the gas boiler is not being used at the same time as the fire is lighting and in fact I am now scared to use the gas heating at any time. Any advice would be greatly appreciated.

heinbloed

....in fact I am now scared to use the gas heating at any time. Any advice would be greatly appreciated.

Since you don't know what to make of the the situation get a boiler/heating engineer in. The installer should have left a manual, should have comissioned the system, should have explained to you how to handle the heating system......

In principle all boilers must be equipped with safety devices so no explosion can happen. But with an installation as you have described this might not be the case, a shoddy job seem to have been done....

Is the circulation pump running when the fire is lit ?

S Connor

Is the circulation pump running when the fire is lit ?[/QUOTE]

Yes it is, there is a stat on the pipes which turns on the pump when the pipe reaches the required temp.

heinbloed

So what is the problem? Are the radiators getting warm, is the domestic water getting warm?

S Connor

Yes they are. The problem is that the pipes in and out of the gas boiler are also getting very hot and the gas is not on.

S Connor

I mean we dont have the gas heating on.

heinbloed

You're describing a system which is very common.
The gas boiler won't turn on until asked to do so.

My heating system works like this as well.

As long as the temperature in the circulated water is high enough the boiler won't turn on. If the temperature drops below the set temperature the boiler will start to fire. Once the circulated water has reached the set temperature the boiler will stop firing. And after a while the circulated water has spend it's thermal energy via the radiators it will be cold enough to kick in the boiler again. And so on.

S Connor

I seem to be doing a bad job of explaing the problem. It's just that I don't think the water being heated by my solid fuel back boiler should be going through my gas boiler. I don't want to use the gas heating at the moment am just worried that the pipes to it are very hot.

heinbloed

It's just that I don't think the water being heated by my solid fuel back boiler should be going through my gas boiler

Why do you think so ?

Has someone said so, the installer maybe?

S Connor

S Connor wrote: »

. It's just that I don't think the water being heated by my solid fuel back boiler should be going through my gas boiler.

You are correct.

Micky Dolenz

S Connor wrote: »

I seem to be doing a bad job of explaing the problem. It's just that I don't think the water being heated by my solid fuel back boiler should be going through my gas boiler. I don't want to use the gas heating at the moment am just worried that the pipes to it are very hot.

You are right. you gas boilers heat exchanger is acting like a radiator now, only all the heat goes out the flue and not into the space it's in. It's highly inefficient.

You need to get a pro to have a look at it, might be a minor fix depending on system design.

heinbloed

Micky Dolenz wrote:

You are right. you gas boilers heat exchanger is acting like a radiator now, only all the heat goes out the flue and not into the space it's in. It's highly inefficient.

A practically absurd guesswork. There is no way any serious efficiency calculation or meassured values can back up this opinion.

Reason:

The house has to be heated. If the gas boiler is used or the solid fuel back boiler is non-relevant.

Using the gas boiler to do this job we can see a DeltaT of about 800 Kelvin, this is the difference between the outside temperature and the gas flame's temperature.
A gas boiler would run with a 90% efficiency to heat the house, losing 10% of the potential thermal energy through the flue gas pipe.

Now to the back boiler's distribution going through the gas boiler:

Here we see a Delta T of about 70 Kelvin, the difference between the flow temperature created by the solid fuel back boiler and the outside temperature.

The professional heating engineer (any schoolboy in this case) knows that the thermal losses via the flue gas pipe of the gas boiler are lower when the gas boiler is not firing, just pumping the circulating water.
One could try to think about the usage of a complicated meassuring device, like for example a finger tip or thermometer at the flue gas outlet, to confirm this.
I know these devices are hardly used by the amateurs, but they make sense.

With the installation described by S Connor where either the gas boiler is used to heat the house or the solid fuel back boiler there are thermal losses via the gas boiler's flue pipe, yes.
Either these losses are high - when firing gas- or these losses are low - when firing solid fuel.
About a 5% or 10% of the potential thermal losses will be achieved when using the solid fuel back boiler.

I'm open to discuss these numbers with professionals.

Micky Dolenz

heinbloed wrote: »

Micky Dolenz wrote:

A practically absurd guesswork. There is no way any serious efficiency calculation or meassured values can back up this opinion.

Reason:

The house has to be heated. If the gas boiler is used or the solid fuel back boiler is non-relevant.

Using the gas boiler to do this job we can see a DeltaT of about 800 Kelvin, this is the difference between the outside temperature and the gas flame's temperature.
A gas boiler would run with a 90% efficiency to heat the house, losing 10% of the potential thermal energy through the flue gas pipe.

Now to the back boiler's distribution going through the gas boiler:

Here we see a Delta T of about 70 Kelvin, the difference between the flow temperature created by the solid fuel back boiler and the outside temperature.

The professional heating engineer (any schoolboy in this case) knows that the thermal losses via the flue gas pipe of the gas boiler are lower when the gas boiler is not firing, just pumping the circulating water.
One could try to think about the usage of a complicated meassuring device, like for example a finger tip or thermometer at the flue gas outlet, to confirm this.
I know these devices are hardly used by the amateurs, but they make sense.

With the installation described by S Connor where either the gas boiler is used to heat the house or the solid fuel back boiler there are thermal losses via the gas boiler's flue pipe, yes.
Either these losses are high - when firing gas- or these losses are low - when firing solid fuel.
About a 5% or 10% of the potential thermal losses will be achieved when using the solid fuel back boiler.

I'm open to discuss these numbers with professionals.

Here's a calculation for you. Zero heat loss through heat exchanger is better then anything above zero. Simples.

On dual systems, one appliance should not be sending heated water through another appliance on the system. Simples.

heinbloed

A professional understands the term "calculation", Micky Dolenz.

A statement like

Zero heat loss through heat exchanger is better then anything above zero. Simples.

is distracting from the facts the OP is looking to verify.

It is factually wrong. There is always a thermal loss where there is a hole in the wall, a flue gas outlet.

Any professionals here in the forum who can do an energetic balance sheet, at least a monetarian balance sheet?

Micky Dolenz

heinbloed wrote: »

You're describing a system which is very common.
The gas boiler won't turn on until asked to do so.

My heating system works like this as well.

As long as the temperature in the circulated water is high enough the boiler won't turn on. If the temperature drops below the set temperature the boiler will start to fire. Once the circulated water has reached the set temperature the boiler will stop firing. And after a while the circulated water has spend it's thermal energy via the radiators it will be cold enough to kick in the boiler again. And so on.

You seem to have the wrong end of the stick. He is saying that when stove is lit it sends hot water through gas boiler. This is not meant to happen.

Heinbloed let's keep it simple, is it usually acceptable to have a secondary heat source impacting on a gas boiler?

heinbloed

How many bags of coal will it cost?

To keep it simple......

heinbloed

heinbloed wrote: »

How many bags of coal will it cost?

To keep it simple......

S Connor

S Connor wrote: »

I seem to be doing a bad job of explaing the problem.

not at all:)

S Connor wrote: »

It's just that I don't think the water being heated by my solid fuel back boiler should be going through my gas boiler.

you are right, a gas boiler is not designed to have a secondary heat source, the impact on the boiler would be dependent on the type of boiler you have, ring the manufacture to ask their opinion rather than leave it to some of the posts:pac: you've had.

S Connor wrote: »

I don't want to use the gas heating at the moment am just worried that the pipes to it are very hot.

The issues are more to do with design issues rather than safety issues( which can't be ruled out), a secondary heat source that can impact on a gas boiler is outside of a manufactures instructions and therefore wouldn't meet gas regulations

S Connor

Many thanks for all the replies even if I do seem to have started an argument here............the thing is I'm still not sure if its ok for my solid fuel back boiler to be sending hot water through my gas boiler. The press the gas boiler is in is warmer then the bloody sitting room!!!

S Connor

gary71 wrote: »

not at all:)


you are right, a gas boiler is not designed to have a secondary heat source, the impact on the boiler would be dependent on the type of boiler you have, ring the manufacture to ask their opinion rather than leave it to some of the posts:pac: you've had.



The issues are more to do with design issues rather than safety issues( which can't be ruled out), a secondary heat source that can impact on a gas boiler is outside of a manufactures instructions and therefore wouldn't meet gas regulations

Thanks Gary. I must have been typing while you were posting this. I will ring the manufacturer in the morning.

Micky Dolenz

S Connor wrote: »

Thanks Gary. I must have been typing while you were posting this. I will ring the manufacturer in the morning.

I can tell you what they'll say. Its not designed for it and your system is flawed. There gas boiler is right and the installation of it is incorrect.

You need a pro who is used to dual systems, as I said earlier, it may be a minor fix.

S Connor

Micky Dolenz wrote: »

I can tell you what they'll say. Its not designed for it and your system is flawed. There gas boiler is right and the installation of it is incorrect.

You need a pro who is used to dual systems, as I said earlier, it may be a minor fix.

Thanks Micky I hope you're right and it is just a minor fix as the rads and water are heating up. The gas heating is (or was, who knows now!!!) definetly all right as it's been working for at least 8 years with no problems. I'm going to have to get the whole lot checked out as I'm now wondering if the non return valve has been fitted incorrectly. I would assume a non return valve is fitted to stop the hot water going through the gas boiler, but you know what they say, NEVER assume and I know nothing about plumbing.

heinbloed

The professional would have told S Connor to check the www for the term cascade heating system. Since the professional would have had a professional training and not just being told which way to carry the tool box.

@ S Connor: it is absolutly all right to install many thermal sources ( here: boilers) in one line. As long as 'the weakest link's' max.parameters - the pressure and the temperature are not - exceeded by the physical input of other elements.

These safety parameters can found in the manuals of the individual boilers.
Pressures can be read as well as the temperatures, these meassurement devices should be installed with all boilers.

Your installer made only one mistake as it seems: he didn't explain you the system.

PS
I might should ad that my Vokera combi condensing gas boiler is installed in the same manner as the boiler of the poster S Connor - two boilers in one line. Controlled once per year by the specialist, certified and insured. No problem. A professional's job.

DoneDL

heinbloed, you cannot ever consider that two heating systems can ever be intelinked in a way that allows for unnecessary heatloss from the home. I will accept that there might be a requirement on occasion to preheat an alternative heating unit to help pickup in response time but not as a standard for a normal install. There is also a difference between the behaviour of a more open solid fuel heat exchanger and the restriction in the heat exchanger of a low content gas boiler.

heinbloed

DoneL wrote:

heinbloed, you cannot ever consider that two heating systems can ever be intelinked in a way that allows for unnecessary heatloss from the home.

How much heat is lost from a boiler which is not operating, DoneL?

The two other posters who have put their mighty professional experience into this thread couldn't answer this. Maybe you can?

All boiler cascades operate in the same way as S Connor has described his system. In a perfect, most energy saving manner.

Numbers please, and no more " you shouldn't ". Or to put it on a simple forum level :

How many bags of coal?

Micky Dolenz

heinbloed wrote: »

DoneL wrote:



How much heat is lost from a boiler which is not operating, DoneL?

The two other posters who have put their mighty professional experience into this thread couldn't answer this. Maybe you can?

All boiler cascades operate in the same way as S Connor has described his system. In a perfect, most energy safing manner.

Numbers please, and no more " you shouldn't ". Or to put it on a simple forum level :

How many bags of coal?

Cheers.

What's the second boiler on your system?

oikster

DoneDL wrote: »

heinbloed, you cannot ever consider that two heating systems can ever be intelinked in a way that allows for unnecessary heatloss from the home. I will accept that there might be a requirement on occasion to preheat an alternative heating unit to help pickup in response time but not as a standard for a normal install. There is also a difference between the behaviour of a more open solid fuel heat exchanger and the restriction in the heat exchanger of a low content gas boiler.

Not to mention system balance

heinbloed

Micky Dolenz wrote:

Cheers.

What's the second boiler on your system?

"What's" means what ?

Before we get to this I remind you of my previous questions here in this thread:

How much thermal energy is lost via a system described by S Connor?

Heinbloed your being a little bit silly again:pac:, I fully understand cascade heating systems because I have commissioned them for Viessmann:cool: have you?

Yes, a lot can be done to a heating systems but they still have to be plumbed right:eek:, with the description of the fault it's easy to identify it's plumbed wrong.
A gas boiler needs to be able to dissipate heat, on newer boilers the boiler monitors flow and return temperatures, there's limit stats fitted to gas boilers all these things can be affected by a back boiler fitted "incorrectly".

heinbloed

Oikster, you're a satirist !

Micky Dolenz

heinbloed wrote: »

Micky Dolenz wrote:



"What's" means what ?

Before we get to this I remind you of my previous questions here in this thread:

How much thermal energy is lost via a system described by S Connor?

What is.

I could do the clac's if I could be bothered, I'm not.

You do realise it isn't a cascade system right?

heinbloed

heinbloed wrote: »

Before we get to this I remind you of my previous questions ?

What is it you do again?( There a question that's gone unanswered.)

heinbloed

Micky Dolenz wrote:

I could do the clac's if I could be bothered, I'm not.

Why not ?

oikster

heinbloed wrote: »

Oikster, you're a satirist !

'fraid not....................keep it simple

Heinboeld, you are funny:D

Micky Dolenz

heinbloed wrote: »

Micky Dolenz wrote:



Why not ?

Because it is pointless. The system has a design flaw. There should be zero loss from any of the heat exchangers while the other is working. To do clac's would only be long, boring and pointless as it is clearly a fault. A fault that should be rectified.

Instead of exchanging witty and informative posts with yourself, I would rather help the question asker and use my mighty professional experience for good

S Connor

Well guys, to put another spanner in the works I have just tried my gas central heating and guess what??? It's not bloody working!!!!!!! So there is obviously a problem as it was working fine last week, before the Grant Triple Pass Back Boiler was fitted.

DoneDL

gary71 wrote: »

heinbloed, you are funny:D

Gary fyp, heinbloed may come across as being mad as a bag of cats but some of his posts do make me dig out the technical manuals , not this one though.

heinbloed

Micky Dolenz, if you consider reality pointless maybe this is the wrong forum to point this out.

You neither have the surface temperature of the gas boiler's heatexchanger, nor it's dimensions nor it's aerodynamic behaviour.
No calculation possible, that's it.

You did not ask for these basic facts.

S Connor turned to this forum because of being "afraid", telling us that the temperature of the heating pipe is high.

And you didn't tell him that this is what heating pipes are designed for. Didn't "bother".

This type of professionalism S Connor has experienced already, his plumber who didn't bother (to explain the system), hence he turned to this forum. And found you, accompanied.


Who doesn't bother.....

Micky Dolenz

S Connor wrote: »

Well guys, to put another spanner in the works I have just tried my gas central heating and guess what??? It's not bloody working!!!!!!! So there is obviously a problem as it was working fine last week, before the Grant Triple Pass Back Boiler was fitted.

We are going to need more info.

heinbloed

S Connor wrote:

Well guys, to put another spanner in the works I have just tried my gas central heating and guess what??? It's not bloody working!!!!!!! So there is obviously a problem as it was working fine last week, before the Grant Triple Pass Back Boiler was fitted.

Is the pipe still hot?

Micky Dolenz

heinbloed wrote: »

Micky Dolenz, if you consider reality pointless maybe this is the wrong forum to point this out.

You neither have the surface temperature of the gas boiler's heatexchanger, nor it's dimensions nor it's aerodynamic behaviour.
No calculation possible, that's it.

You did not ask for these basic facts.

S Connor turned to this forum because of being "afraid", telling us that the temperature of the heating pipe is high.

And you didn't tell him that this is what heating pipes are designed for. Didn't "bother".

This type of professionalism S Connor has experienced already, his plumber who didn't bother (to explain the system), hence he turned to this forum. And found you, accompanied.


Who doesn't bother.....

What he said was enough to ID a fault. Other stats aren't needed. A fault has already been established. I doubt a house holder can tell me the exact temp of a pipe.

I think all people understand that pipes on a heating system can handle heat. You are missing the point. Some heating pipes aren't meant to get hot sometimes. The OP, with admittedly no plumbing knowledge, had the smarts to cop that. It's telling that you don't.

In the first few lines his problem was identified, no other facts were needed.

so what is the second boiler on your system?

S Connor

Pipes not hot now because coal fire is out. Gas system will not turn on. Red button lighting saying "press to reset" and when I do press it just seconds later it's lighting up saying "press to reset" again.