Advice sought: Heating and Hot Water, Insufficient Stored Hot Water

[BillyCasper]

Our problem is recent and that the stored hot water is running out too quickly.

I will call a plumber tomorrow, but like to be prepared with some idea.

We have:

1. A Honeywell controller, with heating and hot water settings, both set to come on twice a day morning and evening.

2. An infamous Potterton boiler that has been repaired recently, again, and next time it happens will be replaced with a Worcester-Bosch following a visit to BOXT.

3. Heatrae Sadia Megalflo 250 litre hot water tank that I have recharged recently.

We do get hot water, but when the timer has switched off both the CH and hot water, the stored hot water runs out much quicker than expected, i.e. half way through a second shower which I reckon should have used less than half the capacity of the stored hot water tank.

I’m thinking that the hot water tank is not getting fully filled. I know naught, but a problem with a Honeywell zone motorised diverter valve keeps popping in to my head.

Any thoughts or advice?

Regards,


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[blackal]

A megaflow 250ltr is a pretty big tank.

Plenty to check:

What temperature is your boiler producing in the HW/CH circuits? Is it up around 70C? That would be what I would want in winter.

The HW tank is probably not controlled with a thermostat (on HW boiler heating) - so if your boiler circuit is low (50c say) then that is as high as your stored water can ever be.

Try heating the tank on the electical immersion bank (check thermostat is set up around 65c)- does that give a higher tank temperature?

Is the motor valve to the Megaflow tank opening fully when called on?

Is the hot water timer set for (say) 2hrs prior to you getting up to shower, and continuing during the showering period? That will increase the recovery of the tank temperature. The first part guarantees that your tank (other issues not withstanding) will be at its hotest just prior to showering)

Any chance that there is something blocking flow to the tank?

If the HW is on at the same time as CH - is the heating water going preferentially through the CH circuit?

Are your showers 'power-showers'? Perhaps the flow through them is too great? try a cheap adjustable shower head or restricting washer in the handset to limit the flow a bit.

What temperature is your hot water? What temperature is your heating water (boiler) going into the tank and coming out? Perhaps the tank coils are furred up and not transferring the heat across.

A lot of questions - but could lead you to identifying the problem.

EDIT: If you have access to an infra-red thermometer, you will be able to tell a lot about what the system is actually doing.

[Ed875]

Pressurised hot water cylinders have two temperature sensors one to control the 'working' temperature and the other an upper safety cutout, they also have a third safety feature of a mechanical blow off if the electrical stats fail; pressured water boils at a higher temperature, so can be very dangerous if allowed to go above 100 deg C and a sudden pressure loss occurs; boiling point of water at the normal operating pressure of 3 bar is around 134 deg C.

Would try taking a reading of the water temperature at a tap, should be around 65 deg C, with the flow pipe from the boiler to the cylinder around 75/80, with from memory a 10 deg heat loss on the return.

Manufacturers blurb can be found here if you've not got this already,

https://www.heatraesadia.com/informa...rature-library

[BillyCasper]

Many thanks for such a comprehensive reply.

I've turned up the thermostat on the Megaflo. The scale is 1 to 5, so I've put it up to 5 which I think corresponds to 70 deg. C.

There are two motor valves. The levers on both are set far left and remained so when I turned on the hot water and then a little later the CH.

When I turned on the hot water, the Megaflo flow pipe became hot and return and outlet pipes warm.

The CH and hot water were off before I got in to the shower this morning, quite common since Covid-19, but shortage of hot water only noticed recently.

Our showers are pretty normal I would say, not high pressure.

I'll see how it goes with the Megaflo thermostat whacked up.

Many thanks again.

[blackal]

Many thanks for such a comprehensive reply.

I've turned up the thermostat on the Megaflo. The scale is 1 to 5, so I've put it up to 5 which I think corresponds to 70 deg. C.

There are two motor valves. The levers on both are set far left and remained so when I turned on the hot water and then a little later the CH.

When I turned on the hot water, the Megaflo flow pipe became hot and return and outlet pipes warm.

The CH and hot water were off before I got in to the shower this morning, quite common since Covid-19, but shortage of hot water only noticed recently.

Our showers are pretty normal I would say, not high pressure.

I'll see how it goes with the Megaflo thermostat whacked up.

Many thanks again.

The megaflow thermostat probably only controls the electrical immersion heater bank - NOT the heating effect of the boiler water.

As mentioned- check what temp your boiler is chucking out.

When is your last HW-on Period? You want one just before your morning consumption of water, so that the tank hasn't cooled overnight

[BillyCasper]

Thanks again.

I'll get a thermometer to check the temperature at the tap.

There isn't a control panel door on the boiler, the case has to be removed to get to the controls. Not sure I fancy doing that.

Hot water ran for two hours this morning.

[blackal]

If you get an IR thermometer, check the very top of the tank/outlet for tank skin temp after heated.

check the inlet and outlet temperature of the heating water while it is heating a (say) 30c tank
Check the outlet temp of the pipework exiting the boiler.

[BillyCasper]

I bought an IR thermometer.

Boiler running about one hour:

Boiler pipes:

61 deg. C. (flow?)
57 deg. C. (return?)

Hot Water Cylinder:

42 deg. C. (top of tank, outlet?)
34 deg. C. (flow)
36 deg. C. (return?)

Ran hot water: 39 deg. C.

Boiler pipes:

61 deg. C. (flow?)
57 deg. C. (return?)

Hot Water Cylinder:

41 deg. C. (top of tank, outlet?)
46 deg. C. (flow)
35 deg. C. (return?)

[g40steve]

My three port valve has been playing up, not getting full temp on hot water, new actuator sorted.

[blackal]

Just returned to this thread after sending you a reply to your PM.

In the PM I assumed you had two motor valve (zone valves) but you may have a single 3-way valve. That alters the advice I gave in respect to changing out the valve head.

I'll send this by PM also.

[BillyCasper]

Just returned to this thread after sending you a reply to your PM.

In the PM I assumed you had two motor valve (zone valves) but you may have a single 3-way valve. That alters the advice I gave in respect to changing out the valve head.

I'll send this by PM also.

PM received, really appreciate the time and effort you put into it.


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[BillyCasper]

Cheers to blackal, given me some comprehensive advice by PM. He must have put some effort and time in to it, so big thanks.


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[blackal]

I type fast.

You're welcome.