Avoiding the pitfalls in heat pump projects
I see few undersized heat pump systems these days thanks to legislation, the widespread use of heatloss calcs and MIS 3005. But heat pump projects still sometimes don’t reach their full seasonal performance potential because they are hobbled by less than optimal installation of emitters or failure to take human factors into consideration. So here are my top three pitfalls to avoid:
1. Spacing the underfloor heating pipes too widely
This one is usually the result of a simple failure to communicate and occurs most often when a project manager fails to ensure that the heating circuit installer has been fully briefed by the heat pump installer. I’ve seen systems where the underfloor installer was obviously under the impression that the system was going to be fed by a boiler and installed the pipes far too far apart for low temperature flows to be effective. This can be particularly hard to fix when the floor screed has already poured on the ground floor and often the only choice is to sacrifice the life of the heat pump and efficiency of the system by turning up the flow temperatures. In short make sure that the underfloor heating team are fully briefed on the flow temperature requirements of the system and that they install pipes close enough together so that the system only requires flow temperatures as specified for the heat emitter guide for your system. Treat spreader plates for pipes (often used on first floor installations) with caution: you need to be careful about insulation underneath them and consider the tog value of the floor covering above.
2. Having to turn up the flow temperature of the whole system to keep bathrooms warm
This actually applies not just to bathrooms but to all small rooms – but is particularly common with bathrooms as they are both small and need to be kept particularly warm. You should consider supplementary heating for little rooms when running underfloor heating. Small rooms with little floor area can struggle to reach temperature before the rest of the house is warmed up and the thermostat switches off the system. It can be far more energy efficient in these cases to have a small towel rail heater boosting temperatures in the bathroom than have to adjust flow temperatures for the whole house. You might even want to consider separately controlled electric underfloor mats in these areas such as our FTT-S twin heating mats rather than running the wet system into these rooms at all.
3. Having to turn up the flow temperatures of the whole system because a thermostat is wrongly positioned
If thermostats are positioned in the naturally warmest part of the room the heating will switch off before the room feels comfortable throughout. This leads to customers complaining and flow temperatures being turned up again. For example, new houses with underfloor heating also often have large expanses of glazing, and customers can feel a chill in those areas of the room long after a nook in the corner by an internal wall to a warmer room is cosy. When positioning thermostats look for places with the greatest air movement and heat loss.