Electric Wet System Heating Problems


Postby Frozen Bambi » Thu Feb 07, 2008 10:19 am

Hi!

Any help would be greatly appreciated. We've recently moved into a house which has an electric boiler with a wet radiator system. We believe it was installed within the last 3 years. It is a Fusion 9KW boiler, situated in the loft, set at 85C. There is a large green water tank in the loft as well. We have 6 radiators in a 2 bedroom house with a kitchen, living room and a bathroom. There is a Drayton control panel in the kitchen which controls the hot water and heating separately. There is also a thermostat - set to 28C. All the radiators have thermostats set to the highest temperature. The radiators upstairs need to be bled every day. The house generally feels cold all the time, and the electric bills are huge. The heating occasionally doesn't come on at all when it is programmed to but starts working again once the system is switched off left for a hour or so and switched on again. This has sometimes happened when we have adjusted the times of the control panel. We are completely baffled by the system it appears to have a mind of it's own! Any ideas or tips to get it working more consistently would be excellent. :)
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Postby ericmark » Thu Feb 07, 2008 4:58 pm

A 9Kw boiler is very small same as 3 std electric fires. So normal temperature for a house is about 20°C and for any water controlled heating system you must have a temperature drop across each radiator of about 10 to 15°C. This means it can push water through all radiators not just the easy ones if all radiators wide open the hard ones will fail. Once water goes through a radiator thermo siphon will assist it further so starving the rest. Should hot water return to boiler it will shut down. I know it seems the wrong thing to do but you need to turn the radiators that do work down on the valve other side of thermostat and stop hot water returning. Try turning them all off then on say one turn only I am sure there is something in projects about setting check valves. Electric is expensive, normally it is used as back-up where for example solar or night storage is also used.
ericmark

Postby Frozen Bambi » Fri Feb 08, 2008 9:33 am

Thanks for your help. The radiators are all very hot at the moment (even the ones with lots of air) so do you think if I do the valve checking it make the rooms warmer? Also the heating tends not come on after it has been off for a few hours as opposed to it shutting down when it should be on. Thanks.
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Postby ericmark » Fri Feb 08, 2008 1:09 pm

Although I have seen the electric boilers in the suppliers I have never fitted one and I don't exactly know how there are controlled. If I have make etc I may find it on the internet with some more details. It must have a pump of some type when it stops working is the pump running? You said in loft maybe there is some protection device to stop it should it become short of water? From your reply is seems its not the check valves but to work out what it could be without more details seems impossible. Having seen gas systems shut down prematurely with poor trimming of check valves it seemed likely electric would do the same. The controls are after all the same only heating source changed.
ericmark

Postby ericmark » Fri Feb 08, 2008 1:45 pm

I found two types of boilers both used 3 x 3Kw heaters and had some type of system to protect themselves but one had the following.
“2. Failure modes
2.1 Boil Over - If the system pump fails or the system is running low in water and exceeds 80ºC, then all three injectors will be disabled, all the LED’s will flash and the pump will continue to run. Heating will only be reinstated when the water temperature falls to 40ºC. If the boil over occurs three times then heating will be permanently disabled until the unit is powered down and powered back up, after investigative work has been done.â€
ericmark

Postby Frozen Bambi » Fri Feb 08, 2008 5:14 pm

Thanks for your investigations. Yes, I think I have seen all the lights flashing once and said there was a light flashing saying there was not enough flow. I haven't been able to check in the loft every time it has happened though. Thank you so much, I will investigate further this weekend.
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Postby Sparkgap » Sat Feb 09, 2008 1:47 pm

Is this an open vented or sealed system? If OV, how high is the feed tank above the boiler and pump as it could be you've not got enough height and pump is cavitating and/or drawing in air.
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