地暖系统的水容量比暖气片系统大，约为暖气片的一倍之多。在改装地暖时如果盲目在原暖气片系统上增设加热盘管，可能导致因水容量增加造成暖气系统动力不足，整个地暖系统难以正常运行和散热。因此在改装时建议增设混水装置，混水装置在循环泵旁增设一个旁通，供水管流量不足时，可由回水管补充一部分流量。
The water capacity of the floor heating system is larger than that of the radiator system, about twice that of the radiator system. If the heating coil is blindly added to the original radiator system when refitting the floor heating system, the power of the heating system may be insufficient due to the increase of water capacity, and the whole floor heating system is difficult to operate and dissipate heat normally. Therefore, it is suggested to add a water mixing device when refitting. A bypass is added beside the circulating pump of the water mixing device. When the flow of the water supply pipe is insufficient, a part of the flow can be supplemented by the return pipe.