DS 40 - Thermal Store / Heat Store

[barrycrook]

Hi All,

I have a thermal store which is heated by the boiler. A second pump also circulates this to the CH. A coil with blend valve provide the HW. It's been rumbling recently (localised boiling? sludge/scale perhaps in the bottom?) and after some research appears it requires either de-sludging or de-scaling. The system is about 20 years old and i moved in 3 years ago, so unsure about the service history.

I have estimated the store holds 980 litres of water. It keeps a constant temperature of 80 degrees.

I have tried 2x Sentinel X400 followed with 2x Sentinel X200 + 2x Sentinel X100, but that fixed it for a short period. But i read on the forums that X400 / X200 is quite weak.

I'm think of using DS 40 next, but unsure of the quantity. Looks like you need 2% dose. So in my case 19.6 litres worth?

I will be turning all the Rads off as they are all fine and heat up well. So just doing the store / boiler.

Can anyone give me any advice?

Thanks

Barry

 

[Andygasman2010]

What's the make/model of your store? If your not sure how about a picture...?

Where is this rumbling noise coming from exactly, the boiler or the store itself? When does it rumble, during store heat-up? When the heating is on? Or when you run a hot tap?

Have you tried draining it off? Does it refil on it's own? A blocked cold feed could mean that it's partially empty and not circulating boiler water properly hence the noise.

Also, 980 litres is way too high it's more likely to be 250 litres or so.

 

[barrycrook]

Hi Andy,

Thanks for your quick reply. Not sure so I have uploaded a picture.

Thermal Store

• barrycrook
• 7 Jul 2010
• 1

Bottom left boiler pump, bolier flow and return (bottom left)<br>top left hot water mixing valve...

The noise comes from the store, seems to be after the boiler has heated it up. There is a tank jacket on it. The top has a F&E tank.

i have drained and filled this up several times, so the flow is ok.

The store measurements are below:
Height - 125cm
Diameter - 50cm

Was working on volume = PI x 0.5^2 x 1.25 = 0.98 cubic meters
0.98 x 1000 = 980 litres

But maybe i have not worked it out very well!

 

[ianniann]

Use the radius, not the diameter, so the volume is a quarter of your calculation.

 

[Razor900]

I would say the best way to get the crap out of that would be to drain it, pull the bottom immersion and wet vac it all out.

Problem with using DS40 will be the new unwanted shower in the room below

 

[barrycrook]

DOH! Thanks ianniann! That works out as 245 litres now

Hmm.. Yes maybe remove the immersion heater Razor! That is not used!

The drain off valve does not work either, probably gunked, so i normally drain from the boiler valve, which leaves the bottom still gunked up!

Will i be able to scrap out the scale thou?

 

[Andygasman2010]

I've never known the store itself to make a noise like that, usually find it's the boiler. Post back when you've cleaned it out, i'd be interested to know how much crap you get out and how much difference it makes.

 

[barrycrook]

Guys,

The wife has informed me the rumble does start from the boiler, then pipes but the loudest rumble / noise comes from the store itself.

Is it possible a lot of gas is being produced by the boiler and then making it's way to the store, where it gets released by the F&E tank?

 

[Andygasman2010]

What make/model boiler is it?

Sounds like it's kettling to me. Maybe the boiler pump isn't working properly, or maybe it's just the boiler heat exchanger scaled/sludged.

The problem with cleaning the boiler heat exchanger is that it's connected to a large store which means any chemical you put in is heavily diluted. You can't remove the heat ex unless you're gas registered but if you drained off the store and connected a flush machine to the boiler flow/returns you could circulate chemicals like that. You'd have to hire one though! Change the boiler pump while you're at it maybe.

Or you could just get a pro in. It's difficult to accuratly advise on here as obviously none of us have experienced your fault. Also, you'd save yourself some money what with all the guess work.

 

[barrycrook]

The boiler is a Baxi Solo WM 50/4RS. not sure if it is a condensing boiler, as have read on forums is not advisable for a thermal store. (short burns to keep store at required temp)

Just doing the maths i put 2 lots of X200 in before which calculating the volume would of been good for a 200 litre system!!

I have 13 Rads (130 litres) + Store 245 Litres = 375 Litre System

So i believe i should at least be putting in double the amount of chemicals!
4 bottles of X200 or something else to at least to see if it does the trick.

Now do i try 4 bottles of X200 or something else?

 

[Agile]

Before deciding what to add you need to assess or guess what the problem is.

If its decided to be lime scale in the boiler then about five of X200 would be about the minimum dosage but I would use it in a much more concentrated solution. In your case I would isolate the store so that one X200 could be used on the boiler only.

If it was decided to be lime scale in the store then I would drain and disconnect it and use HCl with only the lower part filled. Whilst there may be some lime scale in the store I dont think thats your problem.

Of course it could also be rusty oxides involved which would need completely different chemicals and treatment.

Whilst you may enjoy trying DIY solutions, a good pro should be able to correctly identify the problem and deal with it quickly.

Tony

 

[Andygasman2010]

Tony, this store will be direct and won't have a heating coil. Unless I miss-understand what you mean.

OP, In my opinion you'd be wasting your money just putting chemicals into it as it is. At the very best you'd do a temp fix and it'd be back in no time. I think you'd benefit from the opinion of a pro onsite here. He'd be able to experience the noise and give a much more accurate diagnosis than anyone can on here.

Don't forget, it could just be a faulty pump!

 

[barrycrook]

Hi Guys,

The store is directly heated from boiler. The immersion heater at the bottom has been disconnected.

Andy, funny enough i was looking at the pump last night. There is a possibility that it could be leaking air into the system when heating the store. Not sure if it could be an airlock, as the noise happens about 2-3 times per day, very loud and seems to be a lot of air perhaps from scale/sludge alone.

I have since dropped the boiler thermostat down from HIGH to 2 and the boiler pump from setting 3 down to 2. Boiler info said to run at level 2 during summer.

So far no noise but it is early days.

I will be bleeding the pump as well to ensure there is no trap air here. But i'm having difficults getting a screwdriver to the bleed value as it is very close to the store. (Pump at bottom left of my original pic)

Thanks

Barry

 

[Andygasman2010]

I'd be suspicious of that pump, maybe change it anyway. You'll have to drain the store down to do that.

When connected to a thermal store the boiler stat should always be set on maximum otherwise the hot water will not perform adequatly. Also keep the pump on speed three for faster hot water recovery.

If you want to take things further yourself without getting the opinion of a pro on-site, i'd recommend changing the pump next.

 

[Agile]

Sorry about mentioning a heating coil. I was trying to describe that only the lower part would be acid treated, to avoid confusion I have edited my earlier posting.

The pump seems to have slot valves which can be used to isolate the pump in theory. In practice they usually leak.

The pump could be turned until the shaft is vertical to bleed air and then rotated back to the horizontal as it should be.

Unless I listened to it I dont see any likely problem with the pump. I would assess the performance with a thermal survey in your case.

I would at first expect scale/sludge in the boiler.

Tony