I returned home after a five week absence, to find the ecological heating system unable to start. The error code indicates 'no flow', any thoughts of what could be the problem.
Water is on and power is on, but a sensor is detecting no flow.
"ecological"? Do you mean a gas boiler? Conventional 2/3 port valves, pump and radiators? Or something else?
A blockage, a valve or pump failure, or a faulty flow sensor?
Theo
Pump has seized up. Given the pre Christmas UK deep freeze you are very lucky not to come back to a flooded and destroyed home if the system wasn't left on in a frost protection mode. It got to -10C round here for a couple of days solid and one house nearby failed catastrophically.
Another where a friend lives suffered CH failure and their so called support contract with a well known gas supplier proved to be useless. They took nearly a fortnight to visit by which time the house had got so cold that pipes froze in the attic and when they thawed - catastrophe!
First thing to try is encouraging the pump to spin - it might just be stiction/rusting causing it to not move.
Usually a big screwdriver will sort that simple fault out.
IIRC the OP told us last year there was no gas. I think the "ecological" to refer to a mix of solar panels + special tariff + timers for off-peak + whatever else I've forgotten.
gis a clue - e.g. just what is telling you there is no flow and where is the pump that's supposed to cause it?
Hi thanks for all replies, I immediately thought of mains water flow, but as you say, maybe the outside heat pump has seized.....perhaps a tap with a big hammer.
Thanks for reply, but I don't know which pump, but MB has suggested the outside heat pump.
Heat pump with air to water system, MB suggests the outside circulator, I hadn't thought of the December low temperature effects.
So I assume this is a monobloc system where the water pipes go outside? Rather than a split system where there's refrigerant lines that come inside?
I wouldn't expect the pump inside the unit to have problems in low temps - is this a fairly new unit? Was the unit isolated while you were away, or was it just turned off at the controller? (There are sometimes settings which can run the pump every few days to keep it in good condition, but won't if it's not powered)
Does the water pipes have glycol (antifreeze) in them? Or do you have antifreeze valves? Glycol should prevent them freezing, whereas antifreeze valves will empty the water in the event of temps inside the (hopefully insulated?) pipework dropping near zero.
Glycol means the water in the water loop is typically blue or green. Antifreeze valves look something like this:
If the water has been emptied it's not surprising the system is complaining of low flow. If the unit can do cooling there is typically a flow switch or turbine to detect flow in the water circuit (in cooling mode, cooling in the absence of water flow can cause ice in the heat exchanger which is very bad news).
If there's no water, do you have a filler tap by which you can refill the water loop?
Theo
Don’t ASHPs require a complex restarting procedure that can take many hours to get it going, with possible compressor failure if it’s not done properly?
No. At least not if you're just doing water-side things on a monobloc - it's just a pipe with a pump and heat exchanger in it.
If you've fiddled with the refrigerant side then perhaps it needs a regas procedure, but monobloc units have the refrigerant entirely enclosed inside where you don't need to tamper with it - it's similar to the way almost nobody needs to repipe or regas their fridge.
Theo
It is more likely to be the pump that circulates the water or whatever working fluid the system actually uses to transfer heat. You really need advice from someone who knows the actual system that you have.
Model number and brand name would help a lot. Otherwise we are guessing.
Also to add: if this is a pressurised system (ie no header tank in the loft) there is likely to be a pressure gauge. Check the gauge to see if it's low
- that would be a symptom if the water in the pipes has been dumped.
Theo
Hi Theo, there is a header tank, about the size of a toilet cistern mounted around 18" above the cylinder, but as noted, maybe the installer forgot the anti-freeze in the outside heat exchanger circuit.
The system has a main cylinder partitioned with 2 heating coils with 3kW immersion heaters, also there is a 4.5kW heat pump outside which has stop working.
The unit is a Daikin EBHQ006B
Right, that's a monobloc. Pipework essentially the same as a gas boiler:
As you say there's toilet-style cistern above the hot water tank, can you dip someth "The software contains special functions using pump and back up heater to protect the complete system against freezing. This function will only be active when the unit is off. However in case of power failure, above mentioned features can not protect the unit from freezing. If power failure can happen at times the unit is unattended, Daikin recommends adding glycol to the water system. Refer to Caution: "Corrosion of the system due to presence of glycol" on page 20 Refer to "[4-04] Freeze protection function" on page 33. Depending on the expected lowest outdoor temperature, make sure the water system is filled with a weight concentration of glycol as mentioned in the table below."
so it sounds like the system will protect itself without glycol in it, but that can't happen if the unit is hard switched off. For that you need glycol or antifreeze valves (a must IMO). It's also possible the installer didn't wire the backup heater so the unit wasn't able to engage this protective heating.
I'm also a little surprised you have a vented system, since glycol oxidises:
"Uninhibited glycol will turn acidic under the influence of oxygen. This process is accelerated by presence of copper and at higher temperatures. The acidic uninhibited glycol attacks metal surfaces and forms galvanic corrosion cells that cause severe damage to the system."
although I don't know how good the inhibitors are and whether they will cope with free air access. Of course that's not a problem if you have antifreeze valves instead.
The checklist for 'flow error' has some things to check:
"Check that all shut off valves of the water circuit are completely open. • Check if the water filter needs cleaning. • Check that the unit is operating within its operating range (refer to "Technical specifications" on page 47). • Also refer to "10.6. Charging water" on page 21. • Make sure there is no air in the system (purge air). • Check on the manometer that there is sufficient water pressure. The water pressure must be >1 bar (water is cold). • Check that the pump speed setting is on the highest speed. • Make sure that the expansion vessel is not broken. • Check that the resistance in the water circuit is not too high for the pump (refer to "13.8. Setting the pump speed" on page 30). • If this error occurs at defrost operation (during space heating or domestic water heating), make sure that the backup heater power supply is wired correctly and that fuses are not blown. • If EKHWSU version of domestic hot water tank is installed, check if the setting of the additional thermostat in the tank switch box is correct (≥50°C)."
Theo
Ok thanks, something to think about. The unit was completely switched off, with two breakers isolating the units.
Sounds like a pump to me. Either jammed up with crud or just failed. Its common knowledge that pumps are intelligent and wait till you are going away to fail!
Brian
If you have not done so already I suggest you check what cover you'd have had for damage to home and contents as a result of absence for 5 weeks and a deliberate decision to have no "frost protection". (Even if you turned off the water before leaving there is the risk of damage between you turning it back on and discovering there are burst pipes.)
It may well be physically damaged then - without mains power it had no way to protect itself from what was a very destructive deep cold spell. You need a service engineer who understands the system to look at it and determine exactly what has gone wrong. Could be quite an expensive mistake - OTOH you might be lucky and it just needs refilling.
Most house insurance policies are void and will not pay out if the property isn't maintained at some sensible minimum frost protection temperature 8C, 12C or even 16C and visited at least once every 31 days. Exact rules vary with the policy but those are rough heuristics.
It is essential to read the small print carefully - especially in winter. ISTR some insist on water drain down and turned off if the huse will be unoccupied for more than 7 days.
I'm not sure where you stand with house insurance if the reason for the temperature being so low is that the CH has failed and so has the "service" company that is supposed to send an engineer around to fix it. My friend is about to cross that particular bridge after massive damage from water leaks in the loft after the thaw. I suspect the boiler service contract will try to wriggle out of paying and so will her insurers.
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