Thermal Diverter Valve, hear me out...

[Duncan62]

Hello BH, another wacky question for discussion.

 

I would like a Thermal Diverter Valve (TDV) in my setup, to send cold water through the FCU in summer, but hot water to the UFH in winter.

I would like this TDV to be self regulating, so that I can set and forget.

 

My thought is to use a Change-over/Diverting valve with a constant temperature Controller.

I would use the valve in reverse essentially.

 

If I set the controller to a MAX of 20deg, the hot water for the UFH at more than 20deg will close the HOT outlet of the valve and open the COLD outlet - this is sent to the UFH.

 

If I set the controller to a MIN of 18deg, the cold water for the FCU at less than 18deg will close the COLD outlet of the valve and open the HOT outlet - this is sent to the FCU.

 

Change-over/Diverting valve: https://esbe.eu/group/products/rotary-valves/vrg230

Constant temperature Controller: https://www.esbe.eu/group/products/controllers/cra200

 

 

comments?

 

 

 

 

[JohnMo]

Wouldn't the constant temperature controller try to mix flows to get a required temp, so may stay at mid point especially between heat pump compressor running cycles?

 

How does your heat pump change between heat and cool? Is it an external switch and dry contacts or software via the controller?

[Duncan62]

2 hours ago, JohnMo said:

Wouldn't the constant temperature controller try to mix flows to get a required temp, so may stay at mid point especially between heat pump compressor running cycles?

 

How does your heat pump change between heat and cool? Is it an external switch and dry contacts or software via the controller?

 

It would try to mix flows yes. 

 

My thinking is if I ask it to mix to a max of 20, at 20 or above it will fully open with cold too try to mix down to 20. But that won't happen as the heart pump controls the temp. 

 

Similar in reverse for cooling water. Mixer had a look temp of 18 so at 18 or below, it will be fully open with hot to try to mix the temp higher. 

 

Hence in each case, the UFH comes off the cold outlet. The FCU comes off the hot outlet. 

 

Temp controlled by the heat pump. 

 

Cooling called for via software from the sensor in the landing.

[JohnMo]

Why not just use a simple diverter. I would look to use a MoMo diverter these use a live signal to move valve between positions and then draw zero Watts once there at either end of the positions. Something like an ESBE MBA.

 

Then upstream of valve have a pipe temp sensor set to switch at 20 degs, anything above 20 is assumed as heating and below is cooling. Use the sensor to switch between the two positions.

 

Use something like this to do the switching - nice simple and cheap plus easy to replace.

https://www.toolstation.com/corgi-pcs-dual-pipe-cylinder-thermostat/p68281?store=LJ&utm_source=googleshopping&utm_medium=feed&utm_campaign=googleshoppingfeed&gad_source=1&gad_campaignid=17808658009&gbraid=0AAAAAD-vLcX0JQPMjDufZ6UOJnzMg2icv&gclid=Cj0KCQjw9obIBhCAARIsAGHm1mSOycvA4DBwLfJ2NQYEJQUeyqdHr4w7n_OiVbj7YKg3ZkM4cP9y4ikaAs_kEALw_wcB

 

 

[Duncan62]

Only issue I see there is that it's not a diverter, the MBA is only on/off for a single pipe.

[JohnMo]

37 minutes ago, Duncan62 said:

Only issue I see there is that it's not a diverter, the MBA is only on/off for a single pipe.

There are 2 or 3 port designs. I use one between heating and DHW. They come up.on ebay from time time pretty cheap

 

https://esbe.eu/group/products/diverting-valves/mba130