Guardian Smartzone Valves

7 Jan 2010
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United Kingdom
Can anyone explain the difference (if any) between the following two Guardian valves:

I'm looking for a valve to be used on new underfloor heating added to an existing central heating system. The plumber doing the work normally uses Honeywell, however the Guardian Smartzone was recommended by someone on the forum, but there are a couple of choices.

The comparison facility on the Guardian website is useless, or there are no differences!
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One of them is a thermal actuator, so it takes longer to open and shut. It works by heating a liquid in the head that pushes a plunger out as it expands. Typically used for underfloor htg zones on a manifold.

The other valve is a simple motor open spring return two port valve, which might be used (for instance) to control the whole manifold.

The motor unit looks a bit like like an Orkli. Best avoided, Honeywell are the de facto motorised valve manufacturer.

One final piece of advice, don't take advice from internet forums unless you already know the right answer.
I have to say that honeywell 2 ports on ufh are a disaster, it might be that they are energised for long periods and tend to get jammed (just my experience ) I thought the thermal actuators were a good idea and will give them a try out, might even try them on unvented cylinders.
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Honeywell are the best for general use but are not rated to be open for long periods. They WILL seize.

I use the Guardian thermal valves for UFH and the weather compensated systems because they are designed to stay open more or less indefinitely.

I wouldn't use them on unvented though as they're to slow to react and not strictly spring closed.
Why would the "energy cut off" need to be spring return ?
Hope I am not being awkward but I cant see how the valve taking a minute to close will make a hugh difference to an unvented cylinder thats overheating, look at the amount of jammed 2 ports that we find with the heating running and the cylinder water at 80c.
Hi Dan, it was your recommendation in an other of my posts that made me consider the Guardian Smartzone valve, however your link (the first shown in my post above) was for the motorised valve and having seen the other thermal valves I wasn't sure which were best for UFH and the Guardian website isn't particularly helpful.

Having spoken to the plumber he explained he normally uses Honeywell motorised valves but was happy to fit another brand.

So the valves that look more like a TRV react more slowly, but are better for UFH. They also have 4 wires instead of 5, is this likely to cause any issues for my plumber?

I like the fact these valves come with a 5 year warranty and they're cheaper than the Honeywell valves (I know cheaper isn't always better - you get what you pay for), but I assume this is because the mechanics are simpler.
Hi Simon, thanks for the information, that makes sense. The valve will be used to control the whole manifold, which has 3 loops, but all to the same area to be heated, which will be controlled by a single thermostat, so separate actuators on the manifold are not required. Given that requests to the boiler for the UFH don't need to be instant I like the idea of the thermal valve.

One final piece of advice, don't take advice from internet forums unless you already know the right answer.

I have to disagree with you on this. I've made some of my best purchases using information on the internet (forums and review web sites) and find it an invaluable source of information and help (especially this forum). It recently helped me diagnose why my new UFH wasn't warming up - because the plumber who connected the manifold did it wrong!!!
Here I am 5 years later and looking to have underfloor heating installed in a bathroom as part of a refurbishment project. In the end I did purchase the Guardian Smartzone Pro 22mm valve for the kitchen UFH and it has worked faultlessly.

I decided to get the same type of thermal valve for the bathroom UFH, but it would appear Guardian don't exist any more and there's no sign of any type of thermal valve when I Google.

Anyone know what happened to Guardian?

Are thermal zone valves still available anywhere?

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