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Discuss Heat bank/thermal Store - Direct or indirect? in the Plumbing Jobs | The Job-board area at PlumbersForums.net

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spaarks

My existing vented cylinder is some 40+ years old and is convection ('gravity') fed (3/4" pipe) from the oil boiler. The boiler is a modern (7 year old) Worcester Bosch. Would I be right in assuming the cylinder is indirect?

Do I have a choice on whether the new cylinder is direct or indirect?

Will I need to have the new system primary pumped? As the boiler is designed for gravity primary is there any potential problem in fitting a pump - can I just fit a pump at the cylinder on the flow side - between the expansion tee and the cylinder inlet?
Is the pump to be controlled by the cylinder stat and if so do I need some sort of protection for the boiler such as a bypass valve to come on when the pump is stopped?

The existing boiler does not require a heat sink, though one is fitted (bathroom radiator).

thanks
 
can you post some pictures of cylinder / boiler setup? please
 
New cylinder indirect (old should be too)

New systems must be fully pumped. Boiler most likely designed to be pumped. Not just a case of adding a pump - the system must be upgraded to a S or Y plan setup with full controls.

If you are replacing the cylinder, switch to unvented or heatstore as both of these are much better than gravity feed.

Pump/stat control issues are addressed by installing a modern programmer and programmable room stat which take care of overrun issues etc in addition to converting to S plan or Y Plan.

Bathroom radiator will not be a heat sink (unless the old system was a back boiler) but more likely permanently into the DHW part of the primary circuit so that your towels are aired in summer when the CH is off.

Change to unvented cylinder or heatstore and make the primary circuit sealed.
 
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can you post some pictures of cylinder / boiler setup? please

Sure. Here is the Worcester manual dwg. My system is the same as fig 8 except there is a small radiator in the primary presumably in parallel with the cylinder coil. My primary is 3/4"on both flow and return.

I can also post a dwg of the electrics but it is quite simple - roomstat calls for the pump and the boiler is controlled by a modern Danfoss programmer. Water temperature is controlled only by the boilerstat.
Scan10007.JPGScan10008.JPG
 
Thanks.
Am I right in saying that the fully pumped is only a requirement where the boiler is being replaced? I will have to look more closely at my system but I suspect going fully pumped may mean major repiping and wiring. Also the bathroom radiator may have to be plumbed into the radiator circuit.

What is the reason I cannot pump the primary from the existing gravity feed ports?

I would like to change the boiler though, so if I do go for fully pumped can I fit the diverter valve(s) near the boiler, ie just after the ch pump, rather than the cylinder? That would mean just one additional pipe from the valve to the cylinder.

If you are replacing the cylinder, switch to unvented or heatstore as both of these are much better than gravity feed.

Yes, that's why I wanted to replace the cylinder. However it seems that a heatbank would be simpler in this case, as the existing system would be unchanged except that the DHW will be heated by a heat exchanger.
I'm sure it's not as simple as that - is it ever!
 
upgrade to fully pumped

Easy to say Rodreguez! Floorboards up in three rooms, bathroom tiles up, wood flooring up... Well if it has to be done it will be - but...here's a direct system by DPS (I will not be using solar or UFH).
Maybe for the moment I can use the gravity Circulation ports (I guess it is meant for solid fuel but should be OK not matter). Then when I change out my boiler I can use the ports on the left hand side. I've emailed DPS about this one.
 
Easy to say Rodreguez! Floorboards up in three rooms, bathroom tiles up, wood flooring up... Well if it has to be done it will be - but...here's a direct system by DPS (I will not be using solar or UFH).
Maybe for the moment I can use the gravity Circulation ports (I guess it is meant for solid fuel but should be OK not matter). Then when I change out my boiler I can use the ports on the left hand side. I've emailed DPS about this one.

i see what your saying but it will have to be done one day. And if your boiler is 7 years old it might come sooner than you think. With fully pumped you also gain much greater control of your system and DHW on seperate thermostat not running off boiler stat.

I looked at DPS heat banks when i done my house. i prefer unvented put a santon in mine. the problem i didn't like was they have to be kept up to temp all the time to deliver hot water whereas an unvented is timed to your requirements
 
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