Eliminate 3 way valve when using y plan with smart rad valves?

[woodman]

My heating system is oil fired y plan, with all rads controlled by Drayton Wiser smart TRVs. The system works well, but I have concerns that the 3 port valve may be starting to intermittently stick. I know how to fix this, however it's really hard to access, and as 3 port valves are a known weak point, I'd like to eliminate it...

As each rad is controlled by a smart TRV, theoretically I don't think I need any additional valve (ie the 3 way valve) to control the overall flow to the heating system. So far, so good That leaves the hot water.

That leaves the hot water.

I'm thinking that a 2 port valve located in the dhw tank heating coil circuit, adjacent to the dhw tank,  powered by the dhw demand thermostat circuit from the wiser programmer would do it.

This in itself would not give dhw priority, however this can be achieved by programming the dhw heating to be on at times when the heating is off. 

(I may have add a bypass or modulating pump to accommodate situations where only 1 radiator is demanding heat)

 

This seems like a logical forward step, does anybody have any experience in doing anything similar, or any suggestions/improvements to this idea?

[ProDave]

Do the job properly, convert to two 2 port valves, convert the wiring to S plan.

 

If they are awkward to get to and you are concerned about maintenance, use Honeywell valves. 

[woodman]

Thanks for your advice. However my thoughts are this:

S-plan and Y-plan were implemented long before smart systems were even thought of, and it could be said that they are at best a compromise considering what was available at the time.

I'm trying to move the system design forward from the 80's technology, however add on systems such as Wiser are aimed at retro fit, thus the installations are tailored towards minimal work to install.

If Wiser (or similar) were to make a single valve which would wirelessly control a 22mm valve, this would be ideal, allowing direct wireless control of heating of DHW  in addition to individual control of each rad. 

In the meantime, I'm looking to eliminate what is unnecessary complexity when a smart control system is implemented onto a traditional Y system

Incidentally, does anybody know of a wireless valve which may do this?

[JohnMo]

People love reinventing the wheel and spending loads to replace something tried tested and works.

 

Smart thermostats and Trvs everywhere is great in theory, but be careful they don't increase oil consumption when the boiler starts short cycling, when it's only got one circuit to manage and has little or modulation.

 

 

[Temp]

+1

As far as I know oil boilers don't modulate at all. The burner is either full on or off.

 

[Radian]

8 hours ago, JohnMo said:

People love reinventing the wheel and spending loads to replace something tried tested and works.

 

Sounds like me - except for the spending loads bit 😄

 

On 20/11/2022 at 09:58, woodman said:

As each rad is controlled by a smart TRV, theoretically I don't think I need any additional valve (ie the 3 way valve) to control the overall flow to the heating system. So far, so good That leaves the hot water.

Do your smart TRV's totally shut off the flow into the radiators? I've had mixed results with zigbee TRV's and wouldn't trust them to stay completely closed outside the heating season.

[JohnMo]

8 hours ago, Radian said:

Do your smart TRV's totally shut off the flow into the radiators

I think it depends on make and model, some are just on or off others will modulate, but suspect most on the market are on or off.  The only thing being smart is the internet connection.

[woodman]

A bit late coming back to the party, but to answer Radian: The wiser radiator valve has to stop the water flow entirely in the event of its own control head not calling for heat, (and therefore in closed position) but  another rad valve in the system is calling for heat, in which event the boiler and pump will be running.

[marshian]

1 hour ago, woodman said:

A bit late coming back to the party, but to answer Radian: The wiser radiator valve has to stop the water flow entirely in the event of its own control head not calling for heat, (and therefore in closed position) but  another rad valve in the system is calling for heat, in which event the boiler and pump will be running.

 

I found using WIser Hub and Smart TRV's I have you could get one rad calling for heat setting the boiler off for a very reduced circuit and a shot while later another rad would call for heat - I think in one particularly cold night I burnt 23kW of gas for no appreciable increase in room temps overnight

 

So I use it to schedule heating periods with a fairly aggressive set back temp at night (almost frost stat setting) this stops individual rads from calling for heat at night

 

What I do like about the Wiser Smart TRV's is they do stay open for a really small trickle of flow and only shut down in the event of a considerable overshoot - so as I'm experimenting with a Weather Compensated flow temp it's actually helped me "tune" the flow thro individual rads especally at the weekend when I have the CH on all day