Hydraulics For Maximum Utilisation Of The Condensing Effect; Underfloor Heating System - Buderus Logamax plus GB162 Technical Manual

6 System examples
6.2.2 Hydraulics for maximum utilisation of the
condensing effect
FLOW-plus system for the Logamax plus GB162
The Logamax plus GB162 gas condensing boiler is
equipped with a FLOW-plus system. It requires no
minimum flow rate enabling easy hydraulics without an
overflow valve.
The Logamax plus GB162-15/25/35 features an integral
high efficiency pump. A high efficiency pump is available
as an accessory for the Logamax plus GB162-45, and
can be installed inside the boiler.
The pumps for the Logamax plus GB162 gas condensing
boilers up to 45 kW can be operated under differential
pressure or output-dependent control. Differential
pressure-dependent control is recommended for systems
with heating circuits directly downstream. For systems
where the heating circuits are connected via a low loss
header we recommend that the heating circuit pump is
controlled subject to output. The control methods for the
pump can be selected at the RC35 programming unit
( tab. 25, page 64).
The output-dependent control of the pump when using a
low loss header enables the system to be used with
maximum utilisation of the condensing effect.
A pump assembly with pump featuring output-dependent
control is available for the Logamax plus
GB162-50/65/80/100. If an external pump is used on
site (e.g. Wilo Stratos 25/1-8 or Grundfos Magna
25-100), operation Δp = constant is also feasible for
heating circuits directly downstream.
6.2.3

Underfloor heating system

Underfloor heating systems are the ideal combination for
Logamax plus GB162 gas condensing boilers on
account of their low design temperatures.
We recommend weather-compensated operation
combined with separate, flow rate-dependent room
temperature control because of the heat-up inertia.
The Logamatic EMS control system with RC35
programming unit is suitable for this.
A temperature limiter (TWH) is required to protect the
underfloor heating system. Connect this at the terminal
strip for electrical connections designated EV (external
interlock) using a floating contact. The contact thermostat
AT 90 can be used as a temperature limiter: product no.
80 155 200.
Combined with the RC35 programming unit, screed
drying with a heating circuit directly downstream is also
possible.
58
1. Underfloor heating system directly downstream
An underfloor heating system directly downstream is only
feasible with pipes that are impermeable to oxygen in
accordance with DIN 4726. This is to prevent damage to
the heat exchanger as a result of oxygen corrosion.
The maximum transferable output of the Logamax plus
GB162 with underfloor heating system directly
downstream is limited (
Logamax plus Maximum transferable output at
10 K temperature differential
150 mbar
residual head
GB162-15
GB162-25
GB162-25 T40S
GB162-35
1)
GB162-45
GB162-50
with UPM 15-70
1)
GB162-50
1)
GB162-65
1)
GB162-80
1)
GB162-100
Table 24 Maximum transferable output of the
Logamax plus GB162 with underfloor heating
system directly downstream
1) With pump assembly – use a low loss header if the amount of
water transported by the internal pump or by the pump
assembly is inadequate.
6 720 645 821 (2010/09) – Logamax plus GB162
tab. 24 and page 70).
200 mbar
residual head
[kW] [kW]
10.0 7.5
16.2 13.9
16.2 13.9
16.9 15.1
21.5 20.7
23.2 25.0
40.7 38.4
40.7 38.4
40.7 38.4
40.7 38.4