Central heating issue

gary83

That time of year again. 

Our heating had been on for around a month with no issues then this week we had hot water with no heating.

We have an ideal boiler connected to a hive hub on an unvented cylinder. The pressure is correct & all radiators have been bled and balanced.

the hive hub is connected fine, operating all lights throughout the house and when the hot water is scheduled to come on the green light indicates on the receiver. The boiler ignites & remains on as scheduled displaying a “C” on the status & a solid white light on the boiler.

however when the heating is turned on by the hive the green light on the hive receiver turns on but the boiler does not fire, the boiler displays a 0 indicating it’s still in standby mode.

I’ve checked inside the airing cupboard, where there’s a functioning central heating pump and two valves.

one of these, a plastic bodied Danfoss hpa2 

https://www.directheatingsupplies.co.uk/danfoss-hpa2-2-port-valve-actuator-only-087n657900?of_tid=MFRWG5B5GEYDSJTGMVSWISLEHUZCM4DSN5SESZB5GI3TGNRX&adGroupId=44503019441&device=m&gclid=Cj0KCQiAkNiMBhCxARIsAIDDKNXM-s6fCMJwwmEJfyoTamc8MWU3Cw00XeYY5kzixHA8C4bAX2sINOkaAmQpEALw_wcB

and one of these, 

https://www.screwfix.com/p/flomasta-27900sx-2-port-motorised-valve-22mm-22mm-compression/8982G?tc=LB6&ds_kid=92700055281954502&ds_rl=1249404&gclid=Cj0KCQiAkNiMBhCxARIsAIDDKNWwDTGDYKqFt70DvepVPYvh87LYMBZiqXCxSaiZv2M5XIY9cUlT0JcaAvTVEALw_wcB&gclsrc=aw.ds

by switching the switch on the danfoss actuator from auto to man the boiler springs to life & all radiators warm up. I thought the obvious solution was that the motor had gone so I replaced the actuator with no improvements & still have the exact same problem.

anybody have any suggestions of things to check?

NSG666

So are you saying that when the hive turns on the heating the Danfoss actuator does not move?
If so turn the heating off, remove the head form the valve and then turn the heating on and see whether the motor in the head turns. If it does then it suggests a sticky valve although the fact that you can move it by hand suggests not. If it doesn't move then it needs electrical tests to find whether the hive is switching properly.

Bendy_House

As NSG says.

The actuator might even 'whirrrr' for a few seconds, but if the actual valve is sticky - and often they are at either end - then the actuator mech might not get all the way over to the 'open' end in order to click the microswitch.

When you do NSG's test, see how easy and smoothly the valve turns. Also check whether it makes a nice firm 'clunk' at each end of travel, or does it sort of 'bed down' into stickiness.

With the actuator still off, if you move the valve into a middle position so you know it's at least partly open, then see if the actuator whirrrs positively and crisply to its end when CH is called for, and makes a distinct 'click' and the boiler now comes on.

gary83

Thanks both, tried that last night and noticed the actuator wasn’t working, checked the connections at that point and have woken up to a toasty warm house this morning