twin coil cylinder in parallel

[ajstoneservices]

PRIMARY COIL CONNECTIONS
Connect the primary connections ( Indirect only ) using the compression connections provided. The primary circuit must be
positively pumped. Gravity circulation is not suitable. Either primary connection may be used as the primary flow. Reheat times
are identical either way. The primary circuit can be open vented or sealed with up to a maximum pressure of 3.5 bar. If you seal
the primary circuit an additional expansion vessel and safety valve is required. The boiler may be Gas, Electric, or Oil but must
be under effective thermostatic control. Uncontrolled heat sources such as some AGA’s, back boilers, solid fuel stoves, etc are
NOT SUITABLE. Please contact our technical department for guidance. Connect the two port zone valve ( indirect only ) into the
primary flow pipework. The direction of flow arrow should be towards the primary flow connection. On twin coil solar cylinders we
have provided an extra thermostat boss should you wish to use it. Again a two port zone valve should be fitted (supplied).
For Solar products refer to pages 10-13.

 

[BigBurner]

In the olden dayes when coils were very small, connecting the boiler flow to the coils bottom connection meant a few extra inches of cylinder was heated at the bottom.

Oddly enough that still applies nowadays!

Connecting the flow to the lower connection will slightly increase the power input and speed the reheat. But its less efficient with a condensing boiler.

I wish these servicemen would stick to changing pumps.

Connecting the flow to the lower connection will NOT increase the power input at all. You need to understand the difference between power and energy. Speed of reheat will be slower, especially partial re-heat.

"But its less efficient with a condensing boiler". The only sensible thing you said.