Fitting a TMV into the hot water supply

[PeteS]

I'm thinking about fitting a Theromstatic Mixing valve valve into the hot water supply just after the calorifier. My thinking is that the hot water gets very hot, far too hot to use without adding cold water, even for washing up. This obviously means unnecessary cold water is drawn into the calorifier whilst hot water is left sitting in the pipe getting cold. If I fitted a TMV adjust to the maximum temperature needed it would reduce the amount of cold water entering the calorfier meaning the water would stay hotter for longer.

Currently there is not enough hot water left in the calorifier in the morning for a shower etc. without starting the engine or webasto.

[Robbo]

I'm thinking about fitting a Theromstatic Mixing valve valve into the hot water supply just after the calorifier. My thinking is that the hot water gets very hot, far too hot to use without adding cold water, even for washing up. This obviously means unnecessary cold water is drawn into the calorifier whilst hot water is left sitting in the pipe getting cold. If I fitted a TMV adjust to the maximum temperature needed it would reduce the amount of cold water entering the calorfier meaning the water would stay hotter for longer.

Currently there is not enough hot water left in the calorifier in the morning for a shower etc. without starting the engine or webasto.

 

You'll use the same amount of hot water (well a tad less due to pipework), as the only difference is that the TMV will mix the hot with cold water instead of you mixing it in your washing up bowl! Although fitting one is recommended to stop scalding, I don't think it would solve your problem.

Edited January 10, 2010 by Robbo

[Keeping Up]

Adding a TMV has exactly the same effect as mixing cold water in the sink.

 

Where a TMV is of benefit is in allowing you to have your calorifer heated up to the same temperature as the engine, without the risk of scalding; but it seems you already have your water at that temperature so it won't help you.

 

For anyone thinking of fitting a TMV; beware that if you buy one that cuts out as a safety measure when the hot water supply reaches too high a tempreature (such as the Caleffi which cuts out at 85 degrees) then after a long spell of running you may not be able to get any hot water at all from it.

[springy]

I fitted one - to reduce the possibility of scalding - but I think I found another benefit,

instead of half filling the washing up bowl with v. hot water & then adding lots of cold

to get it to a point where I could actually put my hands in it to do the washing up, I

now use less of my stored hot water and less water in total as I end up with the

bowl only half full - just enough to do the washing up!

 

springy

[nb Innisfree]

I think the thermostatic shower mixer reacts better to cooler (less hot?) hot water, tends to make the valve less sensitive to adjustment.

[steve hayes]

I think the thermostatic shower mixer reacts better to cooler (less hot?) hot water, tends to make the valve less sensitive to adjustment.

 

We fitted a thermostatic shower to Blue Moon and it works brilliantly and when I install the washing machine (soon the boss says) I am planning on fitting another one to feed the m/c with 40deg water into the cold fill inlet and hopefully saving the water heater from coming on.

 

Has any one tried this out ?

[Robbo]

We fitted a thermostatic shower to Blue Moon and it works brilliantly and when I install the washing machine (soon the boss says) I am planning on fitting another one to feed the m/c with 40deg water into the cold fill inlet and hopefully saving the water heater from coming on.

 

Has any one tried this out ?

 

The barge Kei looks to have

 

[trogstig]

Just remember to fit a one-way valve between the TMV and calorifier, otherwise your tank full of hot water will be gradually cooled throughout the day.

 

I didn't discover this detail until my new system had been refilled for the third time - having struggled with a leaking immersion heater blanking plate that refused to respond to PTFE tape: mostly due to a burr on the edge of the plate.

[ditchcrawler]

Just remember to fit a one-way valve between the TMV and calorifier, otherwise your tank full of hot water will be gradually cooled throughout the day.

 

I didn't discover this detail until my new system had been refilled for the third time - having struggled with a leaking immersion heater blanking plate that refused to respond to PTFE tape: mostly due to a burr on the edge of the plate.

I think ours, which I haven't fitted yet has non-return Valve built in. When I do fit it I will have to work out how to drain it in the winterisation.

[nb Innisfree]

The barge Kei looks to have

 

 

We have bypassed TMV for our w/m, this allows full temp water for hot wash, our w/m (Bosch) will mix water to correct temp. Doesn't your w/m have this mixing facility?

 

Edited to add: Just realised you have cold fill w/m

Edited January 12, 2010 by nb Innisfree

[Robbo]

We have bypassed TMV for our w/m, this allows full temp water for hot wash, our w/m (Bosch) will mix water to correct temp. Doesn't your w/m have this mixing facility?

 

Is your Bosch a small washing machine? If so which model, as having a w/m which takes hot and not just cold seems better on a boat!

[blackrose]

I think ours, which I haven't fitted yet has non-return Valve built in. When I do fit it I will have to work out how to drain it in the winterisation.

 

My TMV must have a NRV built in too because I've never had a problem. It's fitted just after the calorifier so it serves all 3 hot water outlets (kitchen sink, bathroom sink and shower).

 

It's certainly stopped me scalding myself after forgetting I've run the engine, but the problem I've had is that I'm in a hard water area and every few weeks the screen (sieve) on the hot water inlet to the TMV gets clogged with tiny bits of limescale and other detritus from the calorifier. It doesnt take much of this stuff to reduce flow - just a few bits. It only takes 5 minutes for me to disconnect that side and clean the screen but I'm wondering if I should just remove the screen and let the bits run through it - or would that lead to a completely calcified TMV?

Edited January 12, 2010 by blackrose

[colin stone]

Virtually all WM are now cold fill - adopted from the continent where combi boilers are the norm, so storage tanks fairly rare. About the only H&C fill are some built in machines. The system onboard KEI, pic above, works well and apart from using the hotwater in the tank, it reduces elec consumption for a wash cycle to approx 100w It does require manual intervention to turn the solenoids off once all the wash filling is complete - about 10 mins into wash.

As for hot water, ours gets up to 85C - just don't keep fingers under tap or wear w/u gloves.

[Trilby Tim]

We fitted a thermostatic shower to Blue Moon and it works brilliantly and when I install the washing machine (soon the boss says) I am planning on fitting another one to feed the m/c with 40deg water into the cold fill inlet and hopefully saving the water heater from coming on.

 

Has any one tried this out ?

It should work in reducing the energy the washing machine has to put in to heat the water, the problem is that the rinse is normally done with cold water, and this would be done with water at 40 degrees in this set up. I don't know if this would effect the washing, but it would mean you'd use a lot more hot water than you need to. Perhaps have a cold feed as well and some way to switch between them after the wash finishes before the rinse.

[ditchcrawler]

It should work in reducing the energy the washing machine has to put in to heat the water, the problem is that the rinse is normally done with cold water, and this would be done with water at 40 degrees in this set up. I don't know if this would effect the washing, but it would mean you'd use a lot more hot water than you need to. Perhaps have a cold feed as well and some way to switch between them after the wash finishes before the rinse.

If you look at Colin's set up you will see he has two solenoid valves, One in a direct cold feed and one in the warm feed I would guess that they are on a changeover switch so after the machine is full of ward water to wash it changes to cold for rinse

[nb Innisfree]

Is your Bosch a small washing machine? If so which model, as having a w/m which takes hot and not just cold seems better on a boat!

 

It's a full size Bosch Maxx hot and cold fill, 7 years old now, taken from our house when we moved on board. The beauty of it is it's ability to mix hot and cold though heater does come on for a short while, I suspect it mixes hot and cold to a slightly lower temp than required then tops up with heater. Older machines used to only let hot water in when doing a 60c wash.

 

Edited to add: Instructions say only to be operated with hot and cold, hot to be 70c max + hot is added on all washes except 30c.

Edited January 12, 2010 by nb Innisfree

[colin stone]

If you look at Colin's set up you will see he has two solenoid valves, One in a direct cold feed and one in the warm feed I would guess that they are on a changeover switch so after the machine is full of ward water to wash it changes to cold for rinse

 

The left hand solenoid in the cold feed is NO (normally open) and the other is NC (normally closed). When switch is turned on, the blended water is supplied to the WM.