Thermostatic blender valve?

Heedtheadvice

Hi all,
I wish to install a new thermostatic blender valve and am looking for suggestions.

I installed one last year but it proved to be a problem so wish to find an economic replacement. The original had non return valves but they started to stick closed; the flow rate was insufficient and on disassembly I found that the orifices were of limited size thus preventing a good flow even on 22mm pipe.

The following is required
Cold feed from mains (may need to fit a pressure reducer valve)
Hot feed from storage tank/cylinder with head of about 4m
flow rate required to exceed 8 l/min (Typically those rates are compatible with bath filling but this one is to feed a washing machine that is only cold fill)
Temperature control (ideally easily varied) max required 38°C and down to 20°C (although a greater range is acceptable)

So far have only found expensive ones meeting NHS specs or cheaper ones that are not very adjustable so any advice readily appreciated.

I realise that this may require separate (i.e. non built in) return valves as their fitting is essential but that would be fine.

patman99

The standard adjustment range for a temperature moderator valve (to give it it's technical name) is 38 - 45 deg. C.

The average price for a good quality one is £60. I have used them for sinks, but never for washing machines.

I'm not suggesting it won't work, but if it does, it will save you more than the cost of the TMV in not having to heat the water inside the machine so much, thus reducing your energy costs.

You will not need a pressure valve as the TMV reduces the cold water flow to achieve the set temperature automatically.

EssexExile

Are you saying you want hot water to your washing machine? Why?

Norman_Castle

How is your hot water heated?
How far from the storage tank to the machine?
How will the blender valve adjust for the rinse cycles?

Ever wondered why washing machines are now cold fill only?

Heedtheadvice

Thanks patman.

To answer the questions:
1. reason is to save money heating cold water when there is a ready supply of already heated hot water. Like most machines it is cold fill supply only.
2. Gas heating and solar used for water heating.
3. Distance to cylinder is about 4 metres.
4. Ignoring rinse cycles as temperature will be set to about 35 degrees C, very similar to maximum temperature of supply in some hot countries. Better rinsing at higher temperatures (than say our winter cold feed at just ten degrees!). Electric heating will still be required in the machine for higher temperature washes.
5 Yes! Hot and cold fill used to be great! Can you explain why please Norman?

EssexExile

Modern washing machines use a tiny amount of water. By the time actual hot water reaches the machine it's already had enough & turns off, so you've paid to heat water that then just fills the pipework. So the machine then heats the cold water it filled with. If you use hot water for the rinses same thing applies, although with multiple rinses some hot will get through but it won't make it rinse any better.

Norman_Castle

Heedtheadvice wrote: »

Thanks patman.

To answer the questions:
1. reason is to save money heating cold water when there is a ready supply of already heated hot water. Like most machines it is cold fill supply only.
2. Gas heating and solar used for water heating.
3. Distance to cylinder is about 4 metres.
4. Ignoring rinse cycles as temperature will be set to about 35 degrees C, very similar to maximum temperature of supply in some hot countries. Better rinsing at higher temperatures (than say our winter cold feed at just ten degrees!). Electric heating will still be required in the machine for higher temperature washes.
5 Yes! Hot and cold fill used to be great! Can you explain why please Norman?

Machines are cold fill only as its cheaper to only heat the water used.
If your hot water supply is free then this may save a small amount of money but heating by gas is rarely free.
From memory my machine uses about 60 litres per wash. Guestimate 15 litres of heated water? Unless you do a lot of washing you will save very little if anything. With a hot wash being topped up by the machine and using heated water to rinse it could be costing more.
Depending on incoming water temperature a 60 degree wash costs me about 13-16p. The majority being water heating, 10p? For two washes per week thats £10 per year. You will still be paying to heat water. After costs how much are you hoping to save?

Heedtheadvice

Essex.
In general I think you are quite right.
In some cases though there could be an advantage. We wash with extra water and rinse with high levels and extra rinses. Being a very soft water area and with one family member sensetive to detergent this makes sense for us. The pipework also supplies other outlets close by and using that blending system last year showed that warmer water enters the machine most of the time. I.e. preheated.

Norman.
Again in general I cannot but agree.
My estimates taking losses into account is that heating water at outlets (or to machines) by gas probably costs about half of heating by electricity, as described above we use maximum amounts of water so it will be significant in our case. When heated by solar via the immersion heater (ignoring the investment costs etc. that are there anyway) the heat is effectively free when excess solar energy is being produced. Looking at generation figures and the like this will be for about half the year only and being stored in a cylinder makes this more useful. Unfortunately washes do not always coincide with times of high production!

We obviously wash a great deal more than in your household averaging somewhere between 1 and 2 washes per day. We must be a mucky lot!! Based upon your estimates (which look very sensible) and factoring pro rata it would probably cost us maybe £75 per annum to use all electric.

If that is correct and assuming a ten year life it pays to use a blender.
Your point about extra use of hot water for finding is a factor I had not considered but that is something we need to be prepared to accept if we want warm rinsing. Certainly warm /extra rinsing removes a greater amount of residual detergent which is probably of greater importance!

Since getting solar, like many who do so, we have been more focussed on energy saving in general and making best use of cost effective solutions such as applying the same principles to the dishwasher so that, by and large it only gets a hot fill. We have made a significant reduction in gas consumption (in the order of 2,000 kWh per annum)so overall it is not costing us to use more power from that source. Very significantly we now have a reduction of nearly 30% (1000 kWh) in electricity purchased. Most of that reduction is using self generation but the figures also show a reduction in our overall consumption. Not huge admittedly but each one adds up to money saving. If we continue to achieve a saving on the washing machine I estimate that will be worth £50 per annum. Hardly a big saving but welcome nevertheless. It would not be worthwhile if I had to pay for a plumber!!

I'll continue to look to see if I can find a good one for the equivalent of a one or two year cost saving but am beggining to doubt if that will be possible. The last one that was c**p only cost £25 but I have been refunded that.

getmore4less

How much do you get selling your surplus to the grid?
How much does it cost to buy it back?


storing the surplus in a hot water tank may not be the most efficient use once you consider the heat losses from storage to point of use.

Norman_Castle

Heedtheadvice wrote: »

Certainly warm /extra rinsing removes a greater amount of residual detergent which is probably of greater importance!

Why, skin irritation? I use non bio as biological makes my skin itch. Using less detergent or an alternative such as soap nuts may help.

Heedtheadvice

Spot on Norman, one family member is very sensitive to detergents so those suggestions are useful. Will have to look up soap nuts!

Getmore4less, it does not quite work like that. The payment is for generation and (unless export of surplus is metered) it is presumed that export equals half generation. That presumed level is also rewarded. Some people achieve that (down to only 50% exported) many do not. The result is that the more of generation that can be self used the better the benefit in terms of decreased purchased import.

You are right that stored hot water (domestically) is not the best in terms of efficiency - over a long time of storage - but it is quite good over the short term of a few hours so worthwhile storing a morning's surplus energy for use later in the day!