use a motorised valve or not.

[aceman3]

I'm putting in a heating system, running off a solid fuel back boiler. My question is whether to use a 3 way motorised valve. On it's normally open position it would allow the DHW cylinder to heat, when it switches it would open up to the radiators.
If i use the motorised valve i can control the flow in the loop. If i leave it out the flow isn't controllable, other than using a check valve on the return.
Also thinking about using a central heating timer to control the system, i.e pump. Was thinking about using a DHW thermostat also. Which would be the best way.

Anyone any ideas?

 

[taydo]

I would suggest you search the net for central heating plans.
building regs must be adhered to so check them out as well

 

[oilman]

You should have a permanent heatleak from the boiler, and having a valve in the circuit is not a good idea. If the open port of the valve is going to be used for hot water, why not leave it out of the circuit altogether? The heat leak ought to be at least a couple of kilowatts.

If I was having a solid fuel back boiler to run the heating, I would have the DHW with its heat leak connected directly, and use a gravity CH circuit, possibly switched by a 28mm 2-port valve, or no valve at all, and turn the radiators on and off.

The problem with a pump is it can cool the back boiler too much if the system water is cold, so there could be long term chimney problems.

As taydo says, you should consult building regs, back boilers have killed!

 

[AlanE]

Oilman & Taydo says consult building regs. but in reality if you are not a registered engineer with CORGI, OFTEC or HETAS then you need to submit plans for building regulation approval. Members of above can 'self certify' any one else needs building reg. approval.

This could well become a stumbling block in the future as and when the government introduces the house sellers pack prior to trying to sell a house. This is a thought the above is a FACT now.

Alan

 

[aceman3]

Thanks for the responses. I was going to have the two rads on the ground floor act as the heat leak. Need a pump as the DHW cylinder is on the ground floor, & there will be four rads upstairs. My query is how best to control the pump so its not running the whole time.