Thermostaticaly controlled mixer shower + angry wife!

[Last Triumph]

Please help...

My wife is doing the 'told you so' dance around the living room because I ignored her request for an electric shower in preference for a faster flowing mixer that I've just spend a fortune on.

Problem is that unless the heating has been on for ages (hours) the hot water in the hot water cylinder seems not hot enough to supply the shower with enough temp to mix with the min amount of cold it must use to function to give enough temp.

It is a 'Hudson Reed 'Lowry' Thermo Mixer' fed with twin 22m pipe from a 1.5 bar pump on a grav fed system. All the locations and head height specs are well within guidlines. Water pressure is good.

Using a pyrometer I've measured the water out of the hot tap at 148F/64C which I understand is max as per regs? Anyhow, it works fine under these conditions.

However, after the kids have had a bath, the temp goes down to 100F/38C whcich gives a tepid shower at best, even when it is on full heat. I guess this is because being a thermo mixer valve, it won't fully switch off the cold if the hot isn't hot enough to give the desired temp, as this would cause pump problems, so therefore the min amount of cold it must let through is dropping the temp too much?

Tonight, after the kid's single bath, I uthe heating on for 1 hour, my wife had a shower and on full heat it was tepid!!!!

Angry 'told you so' wife....

Please help.

Why is the water in my cylinder only 100F after just one bath despite then putting the heating on for 1 hour?

Anyone else got a mixer that needs 148F 24/7 to get a decent shower?

Surely I haven't got to run the heating for hours and hours (£££££) just to have an on demand shower?

 

[chrishutt]

You probably need to upgrade your hot water cylinder. Modern cylinders have a much bigger heat exchanger coil in them and so reheat more rapidly. You could also consider increasing the capacity of the cylinder. Also you need to look at the circulation from the boiler to cylinder - is this gravity or pumped? And don't forget to check the capacity of the cold water cistern supplying it all.

 

[sooey]

If you want faster flowing hot water you have to make sure that your hot water supply is big enough to cope, how big is your h/w cylinder, how is it heated. It sounds like you will have to spend a bigger fortune upgrading your existing system to allow your shower to give you what you want it to. Your wife's I told you so dance sounds pretty justified I reckon, I'm glad I'm not you.

 

[JohnD]

Yes, sounds like gravity feed to cylinder to me, unless there is something wrong with the valve and too much heat is going to your radiators.

can you post a pic of the pipes around the cylinder?

What insulation do you have round the cylinder, and the pipes between the boiler and the cylinder?

 

[Last Triumph]

The house is fairly new and is a pumped system with 22mm pipe almost everywhere.

I'm no expert so please forgive me if I sound like a prat here, but the problem doesn't seem to be the quantity of water available, it seems to be that my heating needs to on for ages to keep it that hot - hence 1 bath later when a load of cold is added to the cylinder to top it up drops the temp to say 100f.

Now I can't stand a shower a 100f - it's too hot for me - so is it true that a thermo mixer must always run some cold if fed froma pump?

Logic tells me that if the valve knob it set to say 90degrees, and the incoming hot water is only 100, then surely it only needs to add a very small amount of cold to give me my perfect shower?

Is my understanding of pumped thermo mixer valves need to to allow a certain amount of cold to flow at all times so as not to strain the pump true?

Hope all that makes sense?

How long do other mixer shower owners run their hot water for to guarentee a hot shower?

 

[JohnD]

the cold feed to the cylinder should be at the bottom, so the water stratifies, and although the bottom of the cylinder is cold, the top stays hot

The shower supply should be taken from the top of the cylinder, so that it receives the hotttest water

If you have a modern cylinder, and fully pumped system, the cylinder should be hot after 20 minutes

Let's see those photos!

Also like to see wheere the cylinder stat is

Do you mean to say that you get a good hot shower eventually?

Can you get a shower with the shower pump turned off?

How hot are the radiators while the cylinder is being heated?

 

[chrishutt]

Why do you have to put the heating on to get hot water? Why don't you just have the hot water on?

 

[Last Triumph]

Wife has just made me add that the 'told you so' dance was danced to the tune of 'I was right'....

Anyhow - in aswer to other points. It is a fairly new cylinder with the usual high density 2" (?) thick foam insulation etc.

Maybe the rads are taking too much heat out?

Problem with my system seems to be that if I try to run the 'water only' function without flow to the rads, the pump goes very noisy as if it is straining against huge back pressure. It sounds awful and can't be right?

If I could correct this, I'd leave the hot water running to maintain the correct cyl temp from say 5pm with the rads to 10pm - long after the rads have turned off.

Could 'rad thermal drain' delay the cyl temp rising that much?

Why is my pump so noisy when the rads are off?

I love my wife, and I love my new shower. I just need them to live together in harmony.

 

[JohnD]

what speed is the pump set to?

Let's see those photos!!!!!!!!!

//www.diynot.com/forums/viewtopic.php?t=99672

Anyway, surely you've got a room stat that turns off the CH once the house has reached its temperature?

 

[chrishutt]

Problem with my system seems to be that if I try to run the 'water only' function without flow to the rads, the pump goes very noisy as if it is straining against huge back pressure. It sounds awful and can't be right?

You should have mentioned this before! This is clearly the root of the problem. Something is blocking the flow through the cylinder coil.

 

[JohnD]

photos! photos!

 

[Last Triumph]

Sorry, by the time I've typed a reply, other have added questions....

Yes, the hot water comes from the top of the cyl.
Yes it is fed with cold at the bottom of the cyl.

I understand that the hot rises to the top, but after a bath a 1 hour of heating, the water is still only 100f (ish) and not the 148 max that it should be. I guess that it is mixing to 'some' degree.

No - the shower doesn't eventually get hot - just stays at luke warm due to what I understand to be due to it only getting 100f water and a minimum mix of cold to stop the shower pump from over loading.

The shower still works (although with less pressure) without the pump, but the temp issues remain the same.

Like I say, when the hot water cyl is full of piping hot water - all is well.

 

[Last Triumph]

Okay, okay - photos on the way - gimmie 10 mins.

Just read the bit about a blocked cyl coil.... Hmm - might be partially blocked as it still gets hot.

 

[Last Triumph]

Right - here's the pics. The pump isn't leaking like it looks - it was a duff gate valve that is now fixed.

Hope th pics answer your questions?

 

[chrishutt]

What a mess! There are a few faults there, particularly the lack of a proper flange connection for the hot supply to the shower.

But first can you check the gate valve on the pipe from the lower coil connection. This may be very nearly shut, thus restricting flow through the coil. Check how close to closed it is, then open it a lot more and see what happens when you pump through the coil.

Meanwhile I'll pick so more holes in your installation.

Later.. the outlet connection from the cylinder coil is only 15mm. This will restrict the flow and the size reduction might be a point where a blockage could arise. You also have a by-pass pipe with a valve, the one that joins the return from the coil just after the gate valve. The gate valve on the by-pass should be almost shut since it is only likely to be required when all the heating circuit TRVs are shutting down.