Ideal Icos HE18 Frost Stat Issue

[oldbutnotdead]

That bypass valve (the gate valve) only wants to be open a fraction, maybe half a turn at most. A proper bypass valve (which can be set to a specific pressure differential) would be far more useful.
'Suggests' doesn't really do it for me, you'd be amazed how powerful the thermal loop effect is when there's a good uphill stretch between boiler and cylinder.
To verify;
Tell Hive you don't want Ch or dhw heat.
Activate frost stat (and disable the other stat).
Go to motorised valves(s), try manual lever (on Honeywell there is little resistance if the valve is already being driven open).
Go to pump, see if it is running (idiot light or noise).
Then go back to frost stat, deactivate it and check valves and pump again.

 

[northie]

That bypass valve (the gate valve) only wants to be open a fraction, maybe half a turn at most. A proper bypass valve (which can be set to a specific pressure differential) would be far more useful.
'Suggests' doesn't really do it for me, you'd be amazed how powerful the thermal loop effect is when there's a good uphill stretch between boiler and cylinder.
To verify;
Tell Hive you don't want Ch or dhw heat.
Activate frost stat (and disable the other stat).
Go to motorised valves(s), try manual lever (on Honeywell there is little resistance if the valve is already being driven open).
Go to pump, see if it is running (idiot light or noise).
Then go back to frost stat, deactivate it and check valves and pump again.

So I did the above and the frost protection kicked in. Checked the pump and it is running. Checked the Honeywell valve and there was still resistance on the lever suggesting the valve isn't opening when under frost protection conditions. To confirm put the system back to normal tried the central heating and the valve opens as it should and zero resistance on the manual lever.

If wired correctly, and the zone valve isnt opening, then the pump wont be running

So possible the zone valve should open with the pump coming on but as it doesn't may be wired incorrectly.

The Icos HE has no boiler run-on i.e. the pump is not controlled by the boiler PCB

If the HE18 doesn't drive the pump when the frost stat kicks in then what does? Is there where I need to look to see why the zone valve isn't opening since the pump is now confirmed to run?

 

[northie]

To summarise what's been done:

• Frost stat set to 5 degrees.
• Pipe stat moved from flow pipe to return pipe.
• Pipe stat turned down from 55 degrees to around 25 degrees.
• Bypass valve moved from fully closed to open half a turn.
• When I tested frost stat earlier the boiler kicked in for approx 1 min and then turned off when return pipe hit 25 degrees (no noises).

I guess proof is in the pudding - see whether it wakes me up tonight. Do I need to pursue getting the zone valve to open when frost stat kicks in or can I leave that fight for another day (i.e. is there any harm)?

 

[Harry Bloomfield]

If the HE18 doesn't drive the pump when the frost stat kicks in then what does? Is there where I need to look to see why the zone valve isn't opening since the pump is now confirmed to run?

My guess, I am not an heating engineer - the boiler and pump are wired to together, fed from the same source, which is normally the valve. The frost stat is wired to power the boiler, boiler comes on so as does the pump.

As I suggested above the frost stat needs to be wired in parallel with your room stat, so that either one can operate the valve - the opening of the valve then switches on both boiler and pump.

 

[northie]

Hmmm maybe I need to have a look at how I wired Hive in then. This is the room stat that triggers the zone valve for CH but I seem to recall the original room stat is still connected as I have to turn this up to 40 degrees so the Hive can control on / off.

See how it goes tonight and then if all works as it should I can take another look over the weekend.

Really appreciate everyone’s help.

 

[DP]

If you have hive, set overnight temperature to 12 degrees and disable the frost stat

 

[northie]

I did consider this. We get down to about 16 degrees in the house when frost stat triggers in garage on 5. So if I took this approach I’d probably need to be more than 12. I guess the issue would be around how quickly the temp drops outside vs the efficiency of the house and how much heat it loses.

 

[oldbutnotdead]

If you have hive, set overnight temperature to 12 degrees and disable the frost stat

That won't protect the boiler (in the garage) very well....

OP If you had a 'real' bypass then current setup would be fine- the garage will tend to be colder than the house so pump only running through the bypass would do, added bonus you don't get disturbed by any rad warming noises.
Since it isn't a proper bypass you'd be better off sorting the control wiring- that gate valve will be reducing the differential pressure between flow and return (so your rads that are now slow to heat will be even slower), also boosting the return temperature (so your boiler may start derating to maintain the ideal flow/return temperature difference.
See what happens tonight- mind, it's warming up here- was -3 this afternoon, it's up to 7 now

 

[DP]

That won't protect the boiler (in the garage) very well..

I think otherwise and have been putting this in practice for last 20 years with no issues.

 

[northie]

Major improvement last night. Frost protect kicked in at about 3:30am and although it did wake me up I didn't actually need to do anything. Obviously semi-concious but I would say came on for 1 min and heard a couple of bubble & bangs right before it turned off. I think the answer is to get the zone valve for CH opening up when frost protect is on so I'll probs look to get someone in shortly.

In the meantime I might do a bit of trial and error - for tonight I am dropping frost stat to 4 degrees (less chance it'll come on / more risk pipe could freeze) and dropping pipe stat to 20 degrees (will turn boiler off sooner / more chance it'll fire a second time). Also opened the bypass another 1/4 turn to increase flow and will see what impact there is on the CH.

Working hard on my assignment at the moment so just need it to stop interrupting my sleep - and if I'm honest there is a little procrastination here too - i.e. fixing the boiler is more interesting than writing a dissertation.

If you have hive, set overnight temperature to 12 degrees and disable the frost stat

BTW - Thanks for the suggestion but will leave this one for now. The lowest temp the house has recorded since beginning of December is 18.5 degrees but the frost protection on garage boiler kicks in every night at 5 degrees. I don't fancy that our well insulated house will lose the 6.5 degrees to get down to 12 before the boiler pipes drop 5 degrees to hit freezing. The insulation in the garage is pretty much none existent (something else worth addressing).

 

[ianmcd]

As this has just started when you installed the hive , my money is on you wiring it in wrong, and never a good idea to leave the existing thermostat connected, turned up or not

 

[northie]

As this has just started when you installed the hive , my money is on you wiring it in wrong, and never a good idea to leave the existing thermostat connected, turned up or not

Agreed, very possibly lazyness on my part. Can’t be sure it started when Hive went in as that was 2017. Maybe the zone valve stopped working then but the symptoms prevailed when the bypass valve was closed. Not sure.

Radiators have been on and still get very hot.

 

[ianmcd]

Radiators have been on and still get very hot.

That just means that the hive is wired to the brown wire on the CH Zone valve, it does not mean that the frost and pipe stats are wired into it, the fact that the frost stat powers the boiler and the pump with the zone valve closed suggests it is not wired correctly , it is possible to wire it like this and let the by-pass circulate, but then you are only protecting the pipes as far as the by-pass

 

[northie]

That just means that the hive is wired to the brown wire on the CH Zone valve, it does not mean that the frost and pipe stats are wired into it, the fact that the frost stat powers the boiler and the pump with the zone valve closed suggests it is not wired correctly , it is possible to wire it like this and let the by-pass circulate, but then you are only protecting the pipes as far as the by-pass

Sorry made the comment about the rads because somewhere I read opening the by-pass has an adverse impact on flow through the zone valves, I.e. some of flow is permanently running back to boiler through the by-pass.

The by-pass is in the airing cupboard. The frost protection is literally serving 2x 60cm of pipe between boiler and where it goes into roof space on an integral garage. So the rest of the piping up to the bypass is actually inside the house.

 

[ianmcd]

Sorry made the comment about the rads because somewhere I read opening the by-pass has an adverse impact on flow through the zone valves, I.e. some of flow is permanently running back to boiler through the by-pass.

The by-pass is in the airing cupboard. The frost protection is literally serving 2x 60cm of pipe between boiler and where it goes into roof space on an integral garage. So the rest of the piping up to the bypass is actually inside the house.

should be fine then as the other pipewor, might be worthwhile changing it to an automatic one, but many succesfully work with just a gate valve set up properly inside the house will be protected by the hive, you just need to get the by-pass setting right