thermostatic (water) valves? (not mixers)

[knighty]

I need a thermostatic valve to go in tp of some 28mm pipe work, to restrict the flow (after a heat exchanger) to keep the temp up to approx. 80'C

it'll need to restrict the flow down to about 20l/min (so the heater can keep up with heating it from cold)

and then open pretty wide (when the feed into the exchanger is already warm so there's more flow at 80'C)


I'm struggling to find one that'll do that... and non of them look very cheap to experiment with


I can't control flow via an inverter pump etc. becasuse mains cold will push through it when a tap is opened

anyone use things like this and have a recomendation?

 

[voipio]

Some idea of the intended use / plumbing arrangement would help to describe the problem.

 

[knighty]

heating side, system boiler heating a flat plate heat exchanger

hot water side, the heat exchanger is in parallel with mains pressure hot water tanks, there's a pump flowing water through the heat exchanger
(hot water tanks connected in series)

cold water inlet is split between the heat exchanger and the hot water tanks and joined after the tanks.... when you draw off hot water it comes from the tanks and heat exchanger... when there's no hot water draw off water is pumped through the heat exchanger and back flowed through the hot water tanks


I already have this up and running, but with 2x 50kw gas water heaters... I've never had much luck with these, always having break downs, always having them serviced/repaired etc. (we use a lot of hot water)

swapping to a system boiler and a heat exchanger will be a much simpler and more reliable system... but I need a way to stop the cold flowing through the heat exchanger too quickly


gas engineer happy to do whatever I want, he's sick of the existing boilers too

 

[daleyd]

Could you use a mixer with the cold feed blanked off? What you’re describing sounds like a radiator thermostatic valve but I’m guessing they wouldn’t flow enough?

A way I’d be familiar with would be (may not be feasible due to complexity/cost, but would give you flexibility) something like a small plc (like a Siemens logo) and motorised valve with a temp sensor on the pipe work?

 

[knighty]

quick and dirty picture

there's no way we'll ever heat enough hot water to meet peak demand, with a bunch of hoses / seam cleaner going all at once, so the tanks act as a buffer

when we're drawing off hot water it's coming from the tanks and from the heater

when we're not drawing off hot water the pump flows hot water backwards through the tanks to heat them
(there's 5 x 300litre tanks, but you get the idea from picture)


I could just restrict down the flow out of the heater... but then he flow will be slow when the water is almost up to temperature too? - once the tanks are warm the heater can heat a larger flow than when they're cold

more flow = better recovery time heating up the tanks


p.s. I'll be spending thousands to swap to a new boiler plus heat exchanger, so not worried about spending on a decent valve/whatever

 

[knighty]

Could you use a mixer with the cold feed blanked off? What you’re describing sounds like a radiator thermostatic valve but I’m guessing they wouldn’t flow enough?

A way I’d be familiar with would be (may not be feasible due to complexity/cost, but would give you flexibility) something like a small plc (like a Siemens logo) and motorised valve with a temp sensor on the pipe work?

I'd be happy with an electronic valve, if I can find something off the shelf?


apologies for my spelling/typos, I'm dyslexic, spellchecker is on the blink,

 

[Mikey D]

@knighty , is this for an abattoir/ meat processing application ?

When I worked in such a place as maintaince engineer., We had a steam boiler , chlorifiers ( spelling ) steam traps etc
We also had mixer valves (spirax sarco iirc) steam and cold water in hot water out , theses fed sterliizer tanks for splitting saws etc ...condensate line back to the boiler feed tank .

Doesn't help in your application tho .....

 

[knighty]

dog food factory

we used to have steam when I was a kid, but it's expensive to maintain, you need insurance etc. etc. etc.

system I have works really well... it's just the reliability of gas water heaters... they're full of valves, sensors, control boards etc. etc.

 

[Mikey D]

Yea was 30 years ago I worked there , looked after the steam boiler ,dosing blow downs , water softeners etc
Insurance inspections , yes lots of maintaince / expense to keep running I guess . They installed a fat rendering plant and after I left ran the boiler on tallow for a while I believe before environmental health or whatever put a stop to it ! .

I think after that they went to a gas fired boiler ...

 

[gaz1]

heat your tanks as hot as you like

fit a 80c thermostatic mixing valve with one side fed from the hot tanks and the other side fed from the cold supply

its roughly the same as the thermostatic mixing valve used on taps to stop users being scalded

 

[Bornfree]

I would contact your local spirax sarco rep. They are not cheap but if you fit what they recommend they will stand by any problems. We used their motor driven valve's on steam but iam sure they will work with hot water.

 

[knighty]

heat your tanks as hot as you like

fit a 80c thermostatic mixing valve with one side fed from the hot tanks and the other side fed from the cold supply

its roughly the same as the thermostatic mixing valve used on taps to stop users being scalded

but then I have no control of the water temperature though the heat exchanger

 

[knighty]

I would contact your local spirax sarco rep. They are not cheap but if you fit what they recommend they will stand by any problems. We used their motor driven valve's on steam but iam sure they will work with hot water.

I'll phone them tomorrow

I thought there's be some simple thermostatic valve I could use

 

[Bornfree]

I'll phone them tomorrow

I thought there's be some simple thermostatic valve I could use

They do thermostatic valves

 

[addjunkie]

You want an electrically controlled valve, with a temperature sensor on the pipe, probably controlled by a small cheap plc.
There are a few members on here who do this stuff for a living or have done @My Old Landy or @Chippie spring to mind probably @daleyd too. Whoops hes already commented

 

[JimmyS]

Only ones I know that are direct acting are the spirax ones, they can do them on a 2 or 3 port valve but like anything from spirax they quite deer, but good.

 

[knighty]

I'm not too worried about cost as long as it isn't crazy, expecting boiler and heat exchanger to come out near £10k


I don't want to spend that much... but I need reliable hot water

 

[JimmyS]

If you want to do it electrically a danfoss cra 112 controller with a esbe 3 p valve and a suitable temp. Sensor should be OK.

 

[JimmyS]

What heater are you going with?

 

[knighty]

gas engineer thinks one from these guys https://idealcommercialboilers.com/

he's worked on one before and says it's good


I just want something reliable/simple, approx. 100kw

any recommendations?