Woodburner/Heat store - do I need a coil fitted?

[picitup]

Hi All

Apologies first I'm a newbie so questions may be a little dense More apologies, 'cos this is a bit long too!

We have some problems that have persisted for months and I'm pretty much going into meltdown!

We had a woodburner with back boiler installed which thermosyphons into a heat store (big hot water tank in the loft). When the store is up to temp, a stat clicks which operates a pump to transfer the hot water to a neutraliser in the airing cupboard. The gas boiler is also connected to a neutraliser.

The problem I have is that the stove often kettles and sometimes boils. The kettling sounds like I've put wet wood on and sometimes I hear a glug. This occurs at a flow from the stove as low as 70 degrees!

The heat store is completely open with no coils fitted. So the connections to the store are stove flow and return and neutraliser flow and return for the take-off to our heating system.

I've monitored temperatures using lots of sensors and found this:

1) Light the stove and stove flow, stove return and heat store temperatures rise as expected, eg 85F, 65R, 75HS.

2) When the HS is up to temp, the pump comes on to pump hot water to the neutraliser. At this point, there seems to be a merging of temperatures in the tank. Stove return, tank temp, heatstore flow and return are all about 70 degrees.

I think the mixing of the temperatures is that the heat store is completely open as it has no coil fitted. When the store pump comes on, stratification is destroyed as the water is mixed from the pump flow. The upshot is that stove return is raised very quickly by 10 degrees, hampering thermosyphoning.

I was wondering if the config of the heat store is OK? If the pumped circuit was connected via a coil or heat exchanger, maybe the turbulence wouldn't upset stratification?

Also, the back of the stove has 4 tappings for the boiler. The installer has used top right and bottom right. Should this be top right and bottom left to enable crossflow? Clearly if flow is 85 and it's kettling, some water somewhere is 100 degrees!

Any offers gratefully received....

 

[picitup]

Hi Again

After reading my long description, I thought a diagram might help.

Thanks
[code:1]............------------------------------------------------------|
............|.....................................................|
........|---|---|F................................................|
....|---|.......|-------------------------------|.............|-------|
....|...|.......|R..............................|.............|.......|
....|...|.Store.|---------------------------|...|.............|F.and.E|
|-------|_______|...........................|...|.............|_______|
|...|.......................................|...|.............
|...|....Loft...............................|...|
|...|.......................................|...|
|...|.......................................|...|
|...|.......................................|...|
|...|.......................................|.|----|
|...|.......................................|.|.O..|..Heat.Store.Pump......|------------|
|...|.......................................|.|____|.......................|............|
|...|F......................................|...|..........................|.Gas.Boiler.|
|...|---|-------|..........................|------------|..................|............|
|R......|.......|..........................|............|..................|____________|
|-------|.......|..........................|.Neutraliser|.....................|..|
........|.Stove.|..........................|............|---------------------|..|
........|_______|..........................|____________|________________________|
................................................................................
.......Dining.Room.................................Airing.Cupboard
[/code:1][/code][/quote]

 

[Agile]

Its more normal to use top and opposite bottom but consult the boiler instructions.

You dont show any radiators but I assume they are connected via the neutraliser.

All your operating conditions look pretty much what I would expect and I dont see whay you are concerned about them.

If the only problem is kettling then you should check and change the boiler connections if required and then consider treatment for kettling like X200 etc. The pipe run also has an effect on the gravity flow rate but a differential of 20°C is probably typical but a little less would be better.

Your posting is very clear and helpful with the only missing information being on what water treatment such as an inhibitor you have.

As your store volume is quite big you will often need four cans of X100 to give the correct dosage.

Tony

 

[picitup]

Hi Tony

Thanks very much for your reply. I spoke to the manufacturer and they said they recommend a diagonal connection as it will make the cooler return water travel across a wider section of the stove, rather than a possible favoured pure vertical path. I guess I'll get someone in to make the change.

Yes, sorry I missed the rads out and these are, as you say, connected to the neutraliser.

My two main concerns are the kettling and possible overheating of the stove. We've had a 7KW conventional stove in that position for 2 years and it's all been fine. Now we have a Dunsley Yorkshire stove which, according to the spec is 9KW to the back boiler and 4KW to the room.

However, the oak beam mantlepeice has warped from the heat and the plaster on the chimney breast is shrinking with a few hairline cracks. This makes me think the stove is overheating and I'm worried about using it long term. On top of this, it's *MUCH* hotter than our old stove and I'm sure must be more than 4KW to the room.

I've not heard of X100 before, but see it's a lime scale inhibitor. My guess is the system has been drained and refilled so many times, there is no inhibitor in it. We live in a hrd water area. Will X100 get rid of any current deposits? I wonder if I have deposits in the back boiler?

Thanks

Steve

 

[picitup]

Well you've made me think now! I took a look round the net and found the manufacturer of the X100 and X200 products here:

http://www.sentinel-solutions.net/en/

I wonder if it is limescale. As mentioned we live in a hard water area, and due the the vast number of installation problems (don't ask) I reckon the system has been drained and re-filled around 15 times, giving the opportunity for more lime scale to form.

I really like the idea of pouring a liquid into the F&E tank. In fact much more than getting someone to remove the stove which weighs 450LB with no water in it!

According to the blurb, it may take a few weeks to work.

If this is the answer then I'll kick myself. I've developed a bit of a nervous twitch over this system and it could all be very simple. I think the installer's nearly had a nervous breakdown too.

Well I'm off down Dover tomorrow to buy some. Enough for 27 rads + heat store + stove, so I'll rob a bank on the way

Thanks again

Steve

 

[Agile]

STOP!

Turn off the 27 rads and just use two bottles of X200 in the system. perhaps turn off at a pump valve?

Keep the gas boiler off if you can so the chemical is concentrated in the wood stove.

If you are lucky it will start being noticeable within a few days.

Its not totally correct but I would advise putting full flow ball valves in the feed pipes to the wood burner so that if any draining has to be done it will not involve draining the whole system again.

Tony

 

[picitup]

Hi Agile

Thanks for the advice. The woodburner has a drain point next to it. If I drain there, it will only drain the burner, flow pipes and heat store. Is this what you mean?

Unfortunately it's not really practical to keep the gas boiler off as my mother-in-law lives in the basement and likes her heat. What I could do though is this:

1) Drain the system at the fire, emptying the fire and heat store.
2) Pour the X200 into the F&E tank and refill the heat store and fire
3) Not light a fire for a couple of days to let it soak??

If I don't light a fire, then the gas boiler will work as normal and there will be no significant dilution of the X200 as the heat store pump won't circulate the water.

I guess I should get a water softener too.

Does that sound sensible?

Cheers

Steve

 

[Agile]

No, totally wrong!

You dont need to drain the boiler yet again!

Turn off rads otherwise you are diluting the X200 even more than the volume of the store does.

Just add the X200 to the F&E tank and drain off about 10 litres to get the X200 into the system

Then operate the wood burner all the time to get the X200 circulating at a high temperature through the boiler.

Tony

 

[picitup]

I might get this right in a minute

I'll do as you suggest and just drain off 10L of water, pop the X200 in the F&E, refill and run the woodburner to get it to circulate the water. The woodburner has a boiler stat which regulates air flow, so I can make sure it doesn't cook with this.

I don't think rads are an issue as the heat store (big water tank) is high up in the loft and the water in there only mixes with rad water when the heat store circulating pump is on. If I turn this off, then no mixing and dilution.

I've found a local place where I can buy X200 for just over 12 quid which I think is a good price, so I'll get some and do as you suggest.

When I've 'done the business' I'll report back and let you know if it worked.

Thanks for all your patience....

Steve

 

[Agile]

Just add the X200 to the F&E tank and drain off about 10 litres to get the X200 into the system

Then operate the wood burner all the time to get the X200 circulating at a high temperature through the boiler.

Tony

No wrong again!

You add the X200 FIRST and then remove 10li from the drain point so that the x200 gets into the system!

Tony

 

[picitup]

Ye gods. I'm not going to change career to a plumber!

Thanks Tony I'll take your advice.

Steve

 

[BigBurner]

This "heat store". It looks like an ordinary cylinder. Is that so?

How do you get hot water to the taps?

A thermal store does not need a neutraliser at all. It is the neutral point with all appliances connected to it and radiators run off it. This looks like an odd Heath Robinson affair.

 

[Agile]

The neutraliser is used because there are two heat sources and it has been chosen to be installed to aid connection of the gas boiler to the wood heated store.

I agree that there does not seem, from what we have been told, to be any need for a neutraliser but its always possible that there are issues that we have not been made aware of.

Tony

 

[BigBurner]

The neutraliser is used because there are two heat sources and it has been chosen to be installed to aid connection of the gas boiler to the wood heated store.

I know what neutralisers are. They are unnecessary using a thermal store. I'm not sure if this "heat store" is a thermal store.

I agree that there does not seem, from what we have been told, to be any need for a neutraliser but its always possible that there are issues that we have not been made aware of.

Tony

It may be that is is an evolved system. That is, bits added as it went along instead of starting from scratch when you reach a point. Those neutralisers are not cheap and a waste of time most of the time. They are an empty vessel with tappings.

I still don't know where the DHW is being drawn off.

 

[Agile]

Many installers think that when you have two heat sources then you MUST use a neutraliser!