Solar Hot water system with air bubles and low pressure

[Donquick]

Hi,

I installed a DIY solar system and new cylinder last winter. My friend, who is a plumber came around and installed much of the system and the central heating at the same time. The solar system is good quality one and comes with a high spec mains pressure cylinder and sophisticated computerised controller (and very professional instructions - not a photocopied piece of paper translated from chinese).

Although we are both solar novices we succesfully commissioned the solar circuit in accordance with the instructions pressurising it with a hand operated pump. The resting pressure is around 3 bar and this was constant for a good period until recently. BTW The plumber installed an automatic pressure releif valve at the top of the system to allow any air to escape.

Quite recently i heard the pump going as usual one morning but sounding very bubbly and it was obvious immediately that there was air in the pump and pipework. The pressure gauge on the controller was showing zero, but the heat was still transfering through the system and the pipes were as i expected temperature-wise. I allowed the system to run for a while and after a while as the temperature on the panels picked up the pressure in the system was back up to 3 bar on the gauge.

This has been going on for about a month now. The heat transfer to the cylinder is working well and all of our hot water is being provided by the solar during this sunny spell we are having (I know this for a fact as I turned the boiler off about two weeks ago and the cylinder is up to temp each night).

Can anybody in the know give some advice please. My plumber friend has moved away from the area and i don't have acces to the hand pump. I have tried to look for one on ebay and can't see anything like it - the only solar commisioning pumps i see are on a trolley and cost hundreds of pounds. We were able to commision the system according to the instructions using the simple hand pump so i don't know why you would need the expensive version (unless that is the root of my current problem).

I have tried bleeding the pump but there is no air present at the front screw with the pump on or off so that isn't a quick fix.

Does anybody know if i am causing damage to anything by lettign it run at low pressure or how i can get the air out (why is the air not rising to the top of the system and why isn't the releif valve working at the top of the circuit).

As you can tell i am confussed and could use some pointers. If nothing more, does anybody know where i can get a hand pump to recharge the system or what they are called.

Thanks,

Don

 

[Agile]

I think your expansion vessel may be failed or incorrectly set up.

Its normal to run solar systems at about 1.5 Bar and to have pressure relief valves opening at about 3 Bar.

You dont say why you are pressurising to 3 Bar. Whose idea was that?

You may need to call a professional!

Tony

 

[Boilerman2]

If you have Flat panel collectors the pipe arrangement is "Serpentine" i.e. one loop running up & down the panel/s - it is not good enough just to pump fluid in with a hand pump , you need a filling/ Flushing unit which like a power flush machine circulates water around the system to remove all air bubbles, the method to fill is to allow the fluid to circulate through the machine for at least 15 minutes, after this time you close the return valve on the machine to allow the pressure to rise to your required fill pressure. you then switch off the machine isolate and remove the flow & return hoses -Job Done! it sounds like you have air trapped in the collectors!

 

[Donquick]

Hi Gents,

Sorry for the delay - i have been out of town for a while. Thanks for the replies I appreciate your help.

Tony, I have checked the paperwork and you are patially right about the operating pressure. It is recommended at 1.8 to 2.3 bar according to the conrtroller manual and slightly higher according to the panel manual. I doubt that the expansion vessel is incorrectly installed as it just connnects to one of the threaded valves on the controller (which comes preplumbed). I don't think that the pressure releif valve comes on at 3 bar as during commisioning the system is run up to 6 bar.

Boilerman, Thanks too. I have reread the commisioning guide and i think i must revise my ealier comment suggesting that we followed the instructions to the letter. I was being lead by my plumber friend and I think he did it his way, to an extent. seeing your description and the one in the manual (which are basically identical) I think i will need to get somebody in to recharge the system properly!

Thanks again both,

Don

 

[Boilerman2]

I'm in suffolk and have Solar charging kit
the follwing may be of use
www.elanar.co.uk

 

[Donquick]

hi Boilerman, Thanks for the post. Yes i would be interested. How much would you charge to come to bury and purge the system.

Or should i contact you through the website that you linked to?

Thanks,

Don

 

[Boilerman2]

Hello Don
Sorry I havent got back earlier but I have been out of the Country on Holiday

if you use the link in my previous post you will be able to make a booking and discuss the cost

Many thanks.