Solar hot water

Wearb

At my daughters house and she said that hot water was very hot.

Red gauge (pics) was reading 105C and blue 55C son-in- law changed circ pump speed while observing flow meter. Red disc never moved.
Should there be such a difference between hot and cold feed?
Should flow meter have changed with pump speed.

cruiser202006

Wearb wrote: »

At my daughters house and she said that hot water was very hot.

Red gauge (pics) was reading 105C and blue 55C son-in- law changed circ pump speed while observing flow meter. Red disc never moved.
Should there be such a difference between hot and cold feed?
Should flow meter have changed with pump speed.

Flow meter is showing no flow. Is pump getting power? What temperature is it showing on controller at the roof??

Wearb

Roof = 53c Pump is running as I can feel vibration and hear speed changes when I move speed switch.

roy rodgers

I've seen them flow meters stick in a position before.
105 degrees is very hot and maybe could be a slight airlock in the system as the glyco would be starting to steam up at that temperature..
Try and bleed the air separator and the pump to see. Good chance of air in the system

Wearb

roy rodgers wrote: »

I've seen them flow meters stick in a position before.
105 degrees is very hot and maybe could be a slight airlock in the system as the glyco would be starting to steam up at that temperature..
Try and bleed the air separator and the pump to see. Good chance of air in the system

I tapped the flow meter with the handle of a screwdriver just in case it was stuck. On really close observation it moves about 1mm when changing pump speed.
Got a tiny bit of air from pump. Exp vessel empty when red gauge showing 73c. Lots of hot water in cylinder, but I wonder if what I have seen and reported here indicates a lack of glycol ?

Wearb

Babysitting tonight so just checked. Cold pipe warm and hot pipe cold. Is that normal at this time of day, 22:00?

Also pump seem to be running all the time and is a little hot to touch, but hand can be left on it.

Gauges right now.

roy rodgers

Looks like the heat is rising up the return by gravity which would bring the pump on and lose its heat from the cylinder..
Some of the control panels have a timer in them so the pump doesn't during the night. Maybe it wasn't set up probably from the start

Wearb

Thanks Roy. Last person out was installer. I was there to let him in. He topped up glycol, but left it circulate for only about 15 min. I had been advised here that it needed to circulate for multiples of that time to purge the air. I questioned him about it and he said that 15 min was fine and that there is a lot of bull sh1t talked about purging air.

I will try and get them a recommendation for a different guy to check it out.

dathi

Wearb wrote: »

I tapped the flow meter with the handle of a screwdriver just in case it was stuck. On really close observation it moves about 1mm when changing pump speed.
?

you have to adjust the flat head screw at the top of flow meter to adjust speed if you have high temps in pipe work at night sounds like the heat is thermosyphoning out of the cylinder . check if the pipes on the solar coil are rising directly up out of the cylinder to the pump station/roof, they should turn down for min 100mm to stop heat leaving cylinder

Wearb

dathi wrote: »

you have to adjust the flat head screw at the top of flow meter to adjust speed if you have high temps in pipe work at night sounds like the heat is thermosyphoning out of the cylinder . check if the pipes on the solar coil are rising directly up out of the cylinder to the pump station/roof, they should turn down for min 100mm to stop heat leaving cylinder

Hi Dathi. Turning the screw makes no difference whatsoever. I put it back to where it was. It looks like the fully open position?
Pipes from coil to control centre/pump are horizontal from coil and then vertical. I don't think there is any down turn. Rising from the pump to attic, horizontal across the attic and then angled up to the panels.
Any thermosyphoning that occurs has very little effect on domestic hotwater ,as the solar coil is at the bottom of the cylinder.

The thing that jumped out at me was that the hot pipe was roasting while the cold return to the pump was cool. In fact it seemed much cooler than the 55c indicated by the gauge.

freddyuk

The difference between running temperatures (Delta T) is normally switch on at 8c (difference) and switch off at 4c although you can tweak these but that would be a standard setting. Having a difference between flow and return over 10c is not correct.
A professional installer/ service engineer (or competent person) would have a pump and reservoir to remove and replace Glycol which will remove ALL the air at the time of commissioning. If they didn't do this they are not professional or indeed competent. You pay someone to come in and tell you to get the air out? Brilliant.
You can easily fit a non return valve to prevent thermal syphoning at night. The collector sensor T1 should be reading pretty much air temperature at night so maybe 10 - 12c max. I would not fiddle with the flow rate until the system has no air and is not losing heat up the flow pipe at night.
You bleed any air from the air scoop on the left - just open the valve until fluid escapes then close it quickly. Use a bowl to catch any glycol mix which escapes. Check the pressure is 2-3 bar on the pressure gauge.
The pump should run between 8c and 4 c then switch off unless there is a cooling function where it may come on to prevent overheating. It should run for a couple of minutes at a time in normal use. If the T1 temperature is lower than the cylinder temperature the pump should be off!
Adding timers just adds complication and a point of failure which could cause major damage. A decent controller will have sufficient functions to cover all eventualities.