Joining Combi system and PV heated tank

[Inti]

Dear Plumbing Forum


I would like your advice on this plumbing possibility.

I inherited a Glow Worm 30cx combi boiler and have had PV panels put on the roof (PV offered best long term investment at the time). As I was gutting the house and there was space I installed a 180 litre unvented tank heated via an Immersun switch from the PV panels This supplies an en-suite shower and the bath. The combi-boiler supplies the main bathroom shower and hot water to all sinks. Having two separate systems seemed the least complicated and cheapest option, and works very well (only 1m[SUP]3[/SUP] of gas used a week since May 1st).


However, as the children get older and will want to use the main bathroom instead of our en-suite, I would like to connect the two systems. My boiler will not take pre-heated water so I wondered if I could put a diverter valve in the hot water pipe coming out of the boiler. This valve (either manual, move the handle when the tank is hot, or automatic triggered by the emersion element) would open to allow hot tank water into the system that feeds the main bathroom shower and sinks.


Is this possible? Is it allowed? Would you have to have non-return valves to prevent any pressure back into the boiler or tank.

The forum’s help would be greatly appreciated. Please forgive any obvious ignorance as to what is and isn’t possible as I am not a heating engineer.

Thank You All

 

[lame plumber]

turn your combi into a system boiler keeping the kitchen fed off the combi hw side, and connect it to the indirect coil on the cyl if it has one otherwise your stuffed, new cyl with coil needed

 

[josh]

Can get a valve that depending on the temp of the water diverts to the boiler if it is a lower temp or bypasses and goes straight to the tap, made for solar hw systems, i'll see if io can find one and give you the link.

 

[josh]

Intasol combi solar diverter valve, so can deffintly be done.
wouldnt want to ever have to do that manually, what a ballache.

SOLAR SYSTEM COMPONENTS

 

[Inti]

Thank you all for your imput. Not sure if I explained myself clearly enough. I believe I can just put an L port 3 way diverter valve to switch hot water from boiler or tank. I have a temp gauge on the tank and readout in the bathroom so the family can see the tank temp. I imagine the flow will be from the tank for most of the year as the PV panels heat the tank easily most days. When the tank isn't hot enough the lever can be moved (certain novelty factor for family). This seems more reliable and has no electrical feed that actuator valve needs.
The system works brilliantly at the moment and connecting the two should make it even more efficient and flexible (manual valve means you can use both showers at the same time).

 

[josh]

You could just make that up with lever valves but would soon become a chore manually doing it, specially if got on shower to realise it was cool and needed diverting, another thig to consider is immersion heaters arnt that quick at reheating dhw compared to a boiler so of showering/drawing a lot of it will soon run out.
The valve i sent the link for doesnt require electric.
Its upto you what you want to do but just a few things to consider.

 

[Inti]

Thanks Josh. Some good points to consider.

 

[Inti]

Hi Josh
Looked into the Intasol valve. I don't have an issue with overly hot water needing to be mixed to a useable temperature as the immersion is set to a maximum temp. I can see that this valve will automatically switch the two systems for me, but at £250 I would be paying for a lot of function that I don't need. This brings me back to either a manual valve or an actuator triggered off the immersion element. The existing plumbing also readily lends itself to this option. Thanks again for your thoughts.

 

[josh]

The actuator would be dearer, sure it would be possible with a solenoid, would need two as im not aware of a potable 3 port(rated for hot water) to be wired to a stat on the outlet of the cylinder.
This way would be way dearer than the valve and a bit of head scratching at first to make it work.
Levers would be cheapest but as said if your like me you'd soon get fed up with switching it, especially the family.
But nothing stopping you so do what you like!
Good luck and Come back and let us kno how you got on

 

[Ermintrude]

Fit a thermostatic mixing valve not blending. Set it to 65c put the blue side to the cylinder outlet, if cylinder hot water comes from there if cold it comes from wombi. Need some Nrvs on each leg tho. Boosh.

 

[Roger Welton]

Just do what Lame says

 

[josh]

Or just leave it as it is maybe?
if it isnt broken don't fix it.

 

[Ermintrude]

Just do what Lame says

Could do this and control the normally open zone valve with an immsun controller in series with immersion. So when immersion energised two port to boiler off. And when no sun boiler on

 

[Inti]

Hi Ermintrude (showing your age there).
This sounds interesting. As I understand it, the boiler would only fire once the tank flow drops below the temp set on the valve. Can I set the thermostat to say, 40c, and the effect be the same? On some less sunny days the tank might only reach 40c but this is still warm enough for a shower. Many thanks

 

[lame plumber]

only reaching 40 will be enough to shower and perfect for breeding legionella in the cyl, which must go upto 60 regularly to prevent this !!!!!!!!!!!!!

 

[Ermintrude]

If it's a copper tank it inhibits the growth of bacteria but you should blast it once a week upto 70c for 3 hours. As when your shower sprays (atomises) the contaminated water u inhale it and get very poorly