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Underfloor heating and radiators

Can you mix underfloor heating and radiators?

In short, yes. Blog over, right? Well, no; it’s always handy to have answers for your customers when they inevitably ask this very question about the available underfloor heating designs and capabilities; we’re sure you’ve been there. So, let’s give you the facts. While underfloor heating is often seen as the new technology on the block, coming along to replace radiators - perceived as the archaic and traditional method of heating - it can indeed work alongside the radiator system for heating.

Options available

One common practice that people tend to opt for, as you’ll no doubt be aware, is the implementation of underfloor heating in a new build; extension, or otherwise. As such, radiators are often kept throughout the rest of the house and UFH installed only in the new section. Because the new build is likely to be concrete screed, it is the perfect time, as well as energy efficient, to install the UFH system.

A further option that many people tend to opt for is applying UFH downstairs and keeping radiators heating the upstairs. Of course this isn’t down to the fact the UFH can’t be applied to a first floor, because it can - particularly as they are frequently a timber suspended construction - it’s primarily down to the perceived practicality and cost-effectiveness of only purchasing a ground floor system.

How do they work together?

With both systems requiring a different temperature of water, it can often be questioned as to how these two systems can work alongside each other. You basically have two approaches. By far the simplest is to design the radiators for a normal flow temperature (lets say 60 degrees C) and have both the radiators and underfloor heating sharing the same feed from the boiler prior to the zone valves, then relying upon the built in blending valve and pump connected to the manifold to lower the temperature to circa 40 degrees C before it enters the UFH system.

The other option is to have the boiler set at a low temperature (so 40 degrees), dispense with the underfloor blending valve, and use oversized radiators which will compensate for the lower flow temperature running in them. Of course the issue then is huge chunks of steel on your walls but….

Two port or three port? S-Plan or Y-Plan? And what about a bypass?

You’ll ideally  go the S-plan route, and use two-port valves to ensure boiler interlock and control, one for the rad circuit and one for the UFH circuit, but this is no different to using S-plan to control one radiator heating circuit and domestic hot water (DHW)  Some planning will need to take place on how you time control the system, so if you are using simple rotary dial thermostats for the rads and underfloor then a two channel timer will be needed (or a three channel to also control DHW). The other option is to use programmable thermostats for the underfloor (one per zone comes as standard) and a separate programmable stat for the radiator circuit.Another consideration is how to achieve an open or bypass zone for the radiators if you use TRV’s on them, so you avoid the situation of closed TRV’s but the boiler running. Our suggestion is to just approach it as normal and have a towel rail or similar without a TRV, or fit an automatic bypass valve. No bypass is needed with the UFH system because the controls and wiring centre provide the necessary electrical interlock that means the boiler doesn’t fire when there is no demand.

It is technically possible to have a mixed system added onto an existing Y-Plan with a three port valve, but our advice is to avoid that world of pain and go S-Plan.

In summary, it’s easy to understand why many customers assume that they cannot expect to combine both systems, but it’s all pretty easy stuff. If you find yourself in the position of dealing with a curious customer and are stuck for answers, send them in the direction of our blog! Alternatively, if you have any further questions related to our underfloor service, or would like to speak to one of our friendly team, don’t hesitate to get in touch! You can contact us on 0333 800 1750, where our team of experts will be eagerly awaiting your call.

We can advise you on how to achieve interlock, and steer you on how to get it all working. It really is simple once you have done it once (but remember Y-plan = “world-of-pain”)

Alternatively, if you are present on social media, you can keep up-to-date with all things Underfloor through our Facebook and Twitter accounts; so, see you there!

Underfloor heating and radiators
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