UFH - EvoHome and reluctant plumber

[kevinsmart]

Kevin, I looked at your previous configuration picture again. In your case too, if you shut off the flow from the boiler completely, wouldn't your UFH pump just circulate the water round the manifold loops, especially since I note you don't the powered actuator heads arent used on the manifold returns, so they will must be fully open.

Yes, that’s correct and what we want to achieve. My point is if you could find a 2-port rotary/modulating valve, rather than 3/4-way, and were to replace your TMV you would face this issue and need an auto-bypass valve.

Alternatively you could use this valve to supply your current setup.

But, so far I can’t find a suitable 2-way for the HM80.

So back to either using a 3-way or 4-way rotary valve and restrict flow. No need for an auto-bypass in this case.

If you just want to eliminate TPI you could use the HM80 to control your pump and zone valve, but it would of course have no control over the flow and you might see overshoots. Maybe less of a problem with OpenTherm but it depends on what your other zones are demanding.

[kevinsmart]

Yes, that’s correct and what we want to achieve. My point is if you could find a 2-port rotary/modulating valve, rather than 3/4-way, and were to replace your TMV you would face this issue and need an auto-bypass valve.

Alternatively you could use this valve to supply your current setup.

But, so far I can’t find a suitable 2-way for the HM80.

So back to either using a 3-way or 4-way rotary valve and restrict flow. No need for an auto-bypass in this case.

If you just want to eliminate TPI you could use the HM80 to control your pump and zone valve, but it would of course have no control over the flow and you might see overshoots. Maybe less of a problem with OpenTherm but it depends on what your other zones are demanding.

Maybe these?!

https://www.ibc.ie/wp-content/uploads/MVN_Datasheet.pdf

https://products.ecc.emea.honeywell....g_gr-vbg2.html

[bruce_miranda]

What might happen if I just used the ON output of the HM80 on a normal 2 port zone valve and have the flow sensor attached to the output pipe of the 2 port zone valve?

[kevinsmart]

What might happen if I just used the ON output of the HM80 on a normal 2 port zone valve and have the flow sensor attached to the output pipe of the 2 port zone valve?

I don’t think there would be any point connecting the flow sensor as the HM80 won’t be able to correlate its (unconnected) rotary position to it. The HM80 can also operate without the flow sensor where it will, using fuzzy logic, try to correlate the difference from set point to a rotary valve position.

Bear in mind though that the HM80’s goal is to balance the heat loss, so the pump will continue to run even when there is only a 1% zone demand. So I suspect your zone would overshoot compared with your current BDR91 TPI setup.

You could maybe replace your zone valve with the 2-port rotary actuator I found above. The actuator wiring appears to be compatible: Neutral, Clockwise, Counter-Clockwise.

[bruce_miranda]

How about something like this
https://www.jtmplumbing.co.uk/centra...d-close-p16224

Also how does one go from the DN20 or 3/4th inch threads to 22mm copper pipes?

[kevinsmart]

How about something like this
https://www.jtmplumbing.co.uk/centra...d-close-p16224

Also how does one go from the DN20 or 3/4th inch threads to 22mm copper pipes?

That looks as if it might do the trick. I guess you will need some compression adapter couplers.

[bruce_miranda]

How did you go from the V5442 to 22mm pipe? The reason I looked at the valve I linked to earlier was because like the V5442 it is DN20 internally threaded. Whereas the VBG2 that you had linked to, seems to be externally threaded which might mean I need to find some adapters.
Maybe something like this should work, I guess?
https://www.screwfix.com/p/compressi...ails_container

[kevinsmart]

How did you go from the V5442 to 22mm pipe? The reason I looked at the valve I linked to earlier was because like the V5442 it is DN20 internally threaded. Whereas the VBG2 that you had linked to, seems to be externally threaded which might mean I need to find some adapters.
Maybe something like this should work, I guess?
https://www.screwfix.com/p/compressi...ails_container

My heating engineer handled all of that.

Probably something like this:
https://www.navitron.org.uk/dn20-to-...male-connector

And some soldered elbows/couplers.

[bruce_miranda]

I finally managed to find a brand new HM80 and the associated 20K NTC flow sensor for sale.
I have no idea what the new solution for a mixer valve control is meant to be if HM80 is now considered obsolete.
I have also bought the 2 port rotary valve. The bought the 3/4th inch (DN20) version because that is the closest to the 22mm copper pipe I have feeding the UFH manifold.
I need to buy two compression irons to go from the valve back to the 22mm copper pipe.
https://www.jtmplumbing.co.uk/centra...d-close-p16224
https://www.jtmplumbing.co.uk//pipe-...iron-p925/s929

The idea is to replace the currently installed NC 2 port motorised zone valve feeding the manifold. I will set the flow temperature required on the HM80 to just a little over what the TRV on the manifold is set to.
This should mean the TRV on the manifold stays almost fully open, as opposed to what it must currently be almost fully closed. So rather than 65C hot water reaching the manifold, the manifold will (in theory) be fed with 35C hot water.
With the HM80 also handling the pump, this should remove the TPI that cannot be removed when using a
BDR91.

Will let people know how I get on, when I can find a plumber to fit this for me. I certainly won't be touching the heating system in the winter and definitely this doesn't class as essential during lockdown.

[kevinsmart]

I finally managed to find a brand new HM80 and the associated 20K NTC flow sensor for sale.
I have no idea what the new solution for a mixer valve control is meant to be if HM80 is now considered obsolete.
I have also bought the 2 port rotary valve. The bought the 3/4th inch (DN20) version because that is the closest to the 22mm copper pipe I have feeding the UFH manifold.
I need to buy two compression irons to go from the valve back to the 22mm copper pipe.
https://www.jtmplumbing.co.uk/centra...d-close-p16224
https://www.jtmplumbing.co.uk//pipe-...iron-p925/s929

The idea is to replace the currently installed NC 2 port motorised zone valve feeding the manifold. I will set the flow temperature required on the HM80 to just a little over what the TRV on the manifold is set to.
This should mean the TRV on the manifold stays almost fully open, as opposed to what it must currently be almost fully closed. So rather than 65C hot water reaching the manifold, the manifold will (in theory) be fed with 35C hot water.
With the HM80 also handling the pump, this should remove the TPI that cannot be removed when using a
BDR91.

Will let people know how I get on, when I can find a plumber to fit this for me. I certainly won't be touching the heating system in the winter and definitely this doesn't class as essential during lockdown.

Good stuff, look forward to hearing how you get on.

The manifold will of course be fed with water between the HM80 min and max set temperatures.