Saving energy with a Triton T90 Shower?

The first step has been to figure out the flow rate of the Triton T90 and the degree to which it heats the water. I measured the header tank water at 13C and the 'preferred' shower temperature at 39C. This 'preferred' temperature is simply the temperature of the water that I leave it set at. The shower is always turned to full power on the Power Selector, and the 'Temperature' control is usually turned to the halfway position.

The flow rate of the shower was measured at 4.35 litres/minute (surprisingly low) and a quick calculation show that the shower is drawing about 7.8kW of energy to heat the water.

(26 degrees x 4200 joules x 4.35 litres) / 60 seconds = 7.8kW

Next I checked the flow rate and temperature change for various flow rates when the Power Selector is set to 'Low' to try to figure out what the energy the small element puts into heating the water. It's about 2.1kW, but I'll confirm this with an energy meter some other time.

And how much will this 2.1kW element increase the water temperature by? In 60 seconds the element puts out 126,000 joules of energy, so if the flow was 1 litre/minute the temperature would be raised by 30C (126000/4200), a flow of 3 litres/minute would be raised by 10C and a flow of 6 litres/minute would be raised by 5C etc... If we want to maintain the shower flow as it currently is at 4.35 litres/min then the element will increase the temperature by 7C.

I'd like to try to keep the required flow at around 4.5 ltrs/min simply so that there is plenty of scope to increase or decrease the flow rate as required, but I suppose there is a good argument for optimising the output so that the shower is more powerful, but as JohnnieK has pointed out, the higher the flow rate through the TMV the higher the pressure loss. Another reason for aiming at a medium flow is that there is likely to be quite a bit of deviation in the temperature of the hot supply that could introduce a bit of error in the output of the TMV that would need to be compensated for with the shower flow control.

SO, if the temperature of the water coming out of the shower needs to be 39C, the temperature of the supply from the Thermostatic Mixing Valve needs to be 32C. AND the pressure loss needs to be minimal for a flow of 4.5 ltrs/min.


A quick search turned up the Watts Aquamix Series 61C TMV from Alma-Valves.ie, and it looks like it might be ideal. Unfortunately I don't know enough about TMVs to judge it so more reading required.

http://www.alma-valves.ie/wp-content/uploads/2011/06/4.-Watts-Aquamix-Thermostatic-Mixing-Valve.pdf

The pressure loss of 280mm across the 1/2" TMV valve is acceptable for a 4.35 litres/minute flow (260 litres/hour), and even with the maximum flow that the Triton T90 can deliver of 7 litres/minute the head loss isn't too bad at 400mm for the 3/4" valve.



Anyway, I'd appreciate any comments and observations before I destroy my Triton T90.:)

Thanks for the input, Joey, but there is no suggestion of pumping through the TWV. Can they not work under the same existing pressure as the Triton T90, ie gravity?

With regards the thermal cut off for the input temperature, I would certainly be interested in an further information that you might have on that, thanks.

Joey the lips wrote: »

From my understanding no they will not. However perhaps a plumber can explain to you better. In simple terms. TMV are ment to have a min operating pressure of around 0.2 bar (which is low pressure) however i find that they do not operate very well at this pressure and are more likely to perform at 0.5 to 1 bar which in ireland is considered high pressure.

Thanks. If you look at some of the previous posts on this subject you can see that we've started tackling this issue. More information is certainly required.

I really appreciate ALL input on this idea, and of course everything to do with plumbing/heating/electricity is potentially dangerous. All the more reason to discuss it in detail before trying it out.

If you want me to present a 'reason to do this' then I'll do so later.

A quick back of the envelop calculation suggests that a household of 5 people who typically spend 7 minutes each in the shower each day could reduce their electricity bill by €286.50 per annum every year. I estimate the cost of purchasing the valve and bits at €140 so this actually might represent one of the best returns of all energy saving investments.

Of course we can look at those issues more closely later.

JohnnieK wrote: »

Coles. Have you rang Triton in Maynooth about this?

I have fitted 100's of TMV 2 and 3 valves in my time and all bar the exception where on pressurized systems a few where not and gave bad pressure drops across the system.

I really think you will damage the shower if you proceed with this. If you are determined I would leave the spare one under test in your workshop for a while to see the long term affects of this.

Good advice, and I can assure you I am proceeding with caution. This thread is all part of the process of examining the idea in detail BEFORE reaching for the spanners and PTFE.

The key is to find the correct TMV so that it will operate under relatively low pressure and with a pressure drop across the valve that is within acceptable limits

That 2m distance is from the base of the tank not the water level.

I'll have to correct you on that. The total pressure of the system is measured from the highest water level.

TPM wrote: »

the t90 is designed to run and control using cold water so as said above the internal components may not hold up well to the warm/hot water entering the shower.

Also if the mixing valve is struggling under the conditions the temperature control may be unpredictable.

If the mixing valve does struggle to control the temperature/ fails or accidentally gets adjusted the T90 has no way to reduce the temperature which could be dangerous.

The theory behind the energy saving is valid, but personally I wouldnt be happy the actual practise of it and i dont think triton or the mixing valve manufactures would approve it either.

IMO a better option would be to install a thermostatic shower along with the electric shower.

Ok, I hear all this advice about it being dangerous, but this thread is about figuring out how to do it safely.

As someone said earlier in this thread... This idea is very Dangerous. Ideas are never dangerous. Ignorance is dangerous. And that is what I hope we can get beyond by examining this idea in a thorough manner.

You have made some very valid points about the risk of excess water temperature entering the Triton T90 unit and I'll try to respond to that later.

Some points on the issue of excessively hot water entering the Triton T90.

-Thermostatic Mixing Valves work. If the correct one is selected for the narrow set of criteria that apply then there is no reason to believe that it will malfunction in any way.

-The amount of error in the TMV would amount to no more than 2 degrees.

-A lockable TMV can be selected to prevent any interference.

-The T90 shower unit has thermal cut-out devices built-in if for any reason there is a sudden rise in water temperature.

-The temperature can still be adjusted in the usual way with the Temperature Control knob.



The Triton T90 Operating and Installation Instructions. A good read. There isn't any mention of a maximum water supply temperature.

On the issue of discussing this project with Triton, I can't see any reason why it would be in their interest to advise on using one of their products in a way that departs from the method of usage as set out in their manual.

TPM wrote: »

I would guess Triton would have no comment only to say the t90 is designed for connection to a gravity cold water supply. so wouldnt be a productive call.

out of interest which model (t,ti,si,z,xr, etc.) is your shower imo the older ones seem to be more robust

The main one in the house is an 11 year old T90si which is still in perfect working order. I haven't serviced it in any kind of way for 5 years now but it never gives any trouble. The one in the workshop is also a T90si and is about 3 years old and looks identical. And I just remembered that I also have another one in a storage box in a shed so I can afford to blow one or two of them up.:)

Billy Bunting wrote: »

IMO, they are all lacking when it comes to the OP's design, although the thermal cut out will safe gaurd any disaster. I would sugest that the first test on your unit would be to run it without the heat setting with your 35o run ning through it to see just how the pump impellor housing and bits cope with the temperature that they defo weren't intended for.

I don't accept that they weren't designed to be able to take a reasonably high temperature cold water supply, but you're right, -if there is going to be a problem that's where it'll be. I have been looking at the process of how the supply water gets into the heater can and there is the potential for difficulties.

Certainly within the heater can there won't be any problem.

deandean wrote: »

Ach coles now ya have me thinking about this in my sleep! So set the system up. Start with your TMV at 15degC and run tests. Then increase TMV in 5deg increments, testing with a good run each time. Be conservative, i.e. if it is working Ok at 40deg, turn the mixer back to 35deg and lock er at that.
Please do post your findings, most interezting!

Thanks deandean. Unfortunately it won't be possible to test the idea in that way because of the limitations of the TMVs. Most of the domestic ones seem to be able to output a blended flow in range of temperatures, but usually that range starts at 32C and increases in increments towards 40+. That's perfect for a supply for the 'Low' setting on the T90 where the small element is using 2.1kW to raise the flow by 7C.

As a side note it would also be possible to use the 'Medium' setting on the Power Selector to make use of the 5kW(?) element. The blended supply would need around 20C so obviously there would be less concerns about the supply water temperature. Of course the benefits would be also greatly reduced and it would probably not be worth doing.

So what needs to be figured out?

- Can the T90 handle a supply of 32C,

- What TMV is most suitable. What else is required. How much will it cost.

and...

- What is the real benefit.

Joey the lips wrote: »

Just a couple of small points to consider.

The hot water needs to get to the pumped electric shower. If its pumped it will have to be reduced to a very low pressure.

You cannot have the hot water overflow into the cold tank. Obvious reasons on this one.

That does raise an issue. With a 1/2" supply and a flow rate of 4.5ltrs/minute it would take about 7 seconds for the warm water to travel the 5m to get from the cylinder to the shower. The instant shower would not be very instant. Not a major problem, but just something else to consider.

With regards to the hot water overflowing to the cold tank I'm not seeing a major problem here, certainly not a problem that doesn't already exist with any hot water cylinder. Perhaps I'm missing something.

Joey the lips wrote: »

The 7 second constant unfor would be enough to starve the shower of water so this will have to be overcome or the shower will trip or burn out.

Sorry Joey, I think I caused a bit of confusion when I said 'the instant shower would not be very instant'. What I meant is that it wouldn't reach it's correct temperature until the water from the hot water cylinder reached it. Of course there will always be a supply of water to the shower unit.

The only problem with the delay in getting the warm water from the cylinder to the T90 is that it will run unpleasantly cool for 7 seconds. When the shower is turned on it is likely to be set to it's new 'preferred' setting, - 'Low' power (the 2.1kw heating element), and a flow rate of 4.5 litres per second (between 4 and 5 on the flow/temperature control knob). The water flowing into the T90 initially will be at around 20C (ambient temperature around the pipework) and the T90 will warm it by 7C to a slightly unpleasant 27C. As soon as the warm blended flow from the TMV reaches the T90 the shower temperature should increase to a pleasant 39C. No smoke or sparks!

With regards to the second part of your post, I'll throw together a sketch to show how I think it might work and we'll see if we can figure out where the problems might be (and any additional measures that are required to overcome them).

No need for non-return valves?