UFH - EvoHome and reluctant plumber

[bruce_miranda]

It took a while (largely due to lack of support for this in the UK) but I now have the HM80 controlled solution for my single-zone UFH in place. And it works great, I no longer see the 1 degree overshoot, the set temperature is reached and maintained within around 0.1 degrees over several hours.

It's entertaining watching the controller make quiet regular small adjustments to the rotary valve to maintain temperature.

One interesting observation was this freezing morning with a 15C setback temperature and 15.5C measured temperature, the controller decided to run the pump, with Evohome indicating a 0% heating demand (but other zones heating). This appeared to stop further heat loss in the zone.

@kevinsmart I realise this is an old thread. But I am wondering if you can shed some light. I too have a mixed system of rads and one large UFH zone. The UFH zone is currently feed using a separate normally closed motorised zone valve. So I have a fairly simple system I.e. BDR91 opens the zone valve, the micro switch in the zone valve operates the UFH pump. My UFH manifold has a manual TRV set to 35C. All the manifold outlets are always open i.e. I am not using electric actuators on each circuit.
So what needs to change, if I move from this to a HM80?

[kevinsmart]

before.jpgAttachment 1731

@kevinsmart I realise this is an old thread. But I am wondering if you can shed some light. I too have a mixed system of rads and one large UFH zone. The UFH zone is currently feed using a separate normally closed motorised zone valve. So I have a fairly simple system I.e. BDR91 opens the zone valve, the micro switch in the zone valve operates the UFH pump. My UFH manifold has a manual TRV set to 35C. All the manifold outlets are always open i.e. I am not using electric actuators on each circuit.
So what needs to change, if I move from this to a HM80?

Hi Bruce,

Please see the attached images, before and after HM80 installation.

You will need to replace your manual TRV/blending valve with a V5433 3-way or V5442 4-way rotary valve, which has flow, return and manifold connections.

An M6063 rotary actuator is mounted on the valve and its opening controlled by the HM80 based on set point and connected flow temperature sensor reading.

The HM80 will control your pump and your UFH zone valve could be wired in parallel.

A few points to note.

It is wise to fit a flow restricting gate valve because when the rotary valves are closed, all flow diverts to the return, which could unbalance your radiator circuit.

When setting up your HM80 zone in Evotouch you'll need to modify the max temperature parameter (default 55C) to suit your floor type. You can also change the min temperature and pump overrun time.

Finally, you will need to change the zone's heating type from 'mixing valve' to 'zone valve' to ensure the zone sends a heat demand to fire the boiler.

Hope that helps, let me know if you need further clarification. Thanks!

[bruce_miranda]

So how do you access the HM80 settings in Evohome? I thought all the HM80 settings were only accessible on the older CM Zone or Hometronic controllers?

[kevinsmart]

So how do you access the HM80 settings in Evohome? I thought all the HM80 settings were only accessible on the older CM Zone or Hometronic controllers?

You’ll find the parameters can be set from Evotouch with the zone set to Mixing Valve type. But when you change the zone type to Zone Valve for boiler control, you can’t access them.

[bruce_miranda]

Could you please post a picture of the HM80 settings page?
Also when changing a Device type doesn't the previous binding get removed?
Why do we have to change it from a Mixing Valve to a Zone Valve device type? Is there a difference in their behaviours?
Also if the Zone type is set from Mixing Valve to Zone Valve, how does the HM80 still perform a mixing function? Won't it just then behave as a relay with an On/Off function like a Zone Valve?

[kevinsmart]

791DA92F-990F-4DCC-93EF-443A0CBA3B30.jpg

Could you please post a picture of the HM80 settings page?

See attached. You don’t need an HM80 to see these, just add a mixer valve zone, quit binding and view the unbound zone parameters.

[bruce_miranda]

Sorry I edited my previous post with a load more questions.

[kevinsmart]

Could you please post a picture of the HM80 settings page?
Also when changing a Device type doesn't the previous binding get removed?
Why do we have to change it from a Mixing Valve to a Zone Valve device type? Is there a difference in their behaviours?
Also if the Zone type is set from Mixing Valve to Zone Valve, how does the HM80 still perform a mixing function? Won't it just then behave as a relay with an On/Off function like a Zone Valve?

This is documented in the Evohome installation guide:
hm80.JPG

The HM80 by default is used in district heating where a boiler demand is not required.

It works perfectly with this setup, I think the important data it needs is the zone set point and current temperature.

Resideo write:

The underfloor and mixing valve controller will learn the mixed water flow temperature required to match the ambient temperature. It wont ever know what the supply temperature is from the boiler and so is designed to modulate the mixing valve to give this temp and will adapt. evohome will know how far the downstairs temperature is from setpoint and will drive the requested temperature from the boiler to match this demand. evohome sends a water flow temperature to the boiler and the boiler modulates the gas rate to deliver this temperature.

[bruce_miranda]

If I use a V5433 3-way rotary valve, and the valve is completely closed, does the Flow from the boiler just form a direct loop with the Return? Or is the Flow shut off, like in a 2 port valve?

My UFH manifold appears to be a lot more complex than yours. But I do have a 2 port zone valve which feeds the manifold. I was wondering, if I replace that 2 port Zone Valve with a 3 port rotary, would that work. That way, I would be feeding the manifold with lower temperature water, and yes then the manifold TRV becomes redundant.

But if the V5433 just sends all that Hot Water back to boiler in a very short loop, then that won't be very efficient for my condensing boiler.

Also another variation, instead of using both the ON and the OFF outputs of the HM80, could I not just simply use the ON output to control my current 2 port zone valve? While having the UFH controlled by the HM80 rather than the micro switch in the zone valve.
I am trying to avoid the TPI function built into the BDR91 from starting and stopping the UFH pump too often. But another alternative I could have used is to make the BDR91 just control the 2 port zone valve and have the UFH pump connected in parallel to the CH pump.

[kevinsmart]

If I use a V5433 3-way rotary valve, and the valve is completely closed, does the Flow from the boiler just form a direct loop with the Return? Or is the Flow shut off, like in a 2 port valve?

My UFH manifold appears to be a lot more complex than yours. But I do have a 2 port zone valve which feeds the manifold. I was wondering, if I replace that 2 port Zone Valve with a 3 port rotary, would that work. That way, I would be feeding the manifold with lower temperature water, and yes then the manifold TRV becomes redundant.

But if the V5433 just sends all that Hot Water back to boiler in a very short loop, then that won't be very efficient for my condensing boiler.

Also another variation, instead of using both the ON and the OFF outputs of the HM80, could I not just simply use the ON output to control my current 2 port zone valve? While having the UFH controlled by the HM80 rather than the micro switch in the zone valve.
I am trying to avoid the TPI function built into the BDR91 from starting and stopping the UFH pump too often. But another alternative I could have used is to make the BDR91 just control the 2 port zone valve and have the UFH pump connected in parallel to the CH pump.

Yes, when the rotary valve is closed all flow is diverted to return.

I used a gate valve to restrict boiler flow to the UFH circuit. With a 4-way valve this is an injection setup with the UFH pump responsible for a constant flow from the valve supply flow to supply return ports.