Hi

Im not a Grant expert but the Grant R32 manual says the following - it this the error?

I wonder how it detects this error.  One would think it was the flow meter but it could be temperature sensors.  You seem to have checked the obvious, the other things I can think of are: Is there a fine mesh filter somewhere (I have one on my Vaillant system that wasnt obvious until the installer pointed it out), is there a real time readout of flow rate which could confirm.  Are there any other real time diagnostics that might tell you whats going on?

I suppose its possible that its a compressor fault - has it been serviced recently?

Thanks for the reply. Yeah there isn't a mesh filter or strainer anywhere in the system, just the mag filter which is clean. 

It probably is due a service alright. Just curious that it only happens when DHW setpoint is increased. I'll try find the flow diagnostics too, to confirm it's a flow rate issue. 

@2019ashp I’ll ask Grant for their thoughts tomorrow… strange that it only happens in DHW.

Posted by: @2019ashp

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Thanks for the reply. Yeah there isn't a mesh filter or strainer anywhere in the system, just the mag filter which is clean. 

It probably is due a service alright. Just curious that it only happens when DHW setpoint is increased. I'll try find the flow diagnostics too, to confirm it's a flow rate issue. 

I don't know the Grant system but this is common when there is air trapped in the tank circuit which causes the water to have reduced flow and reduced heat exchange causing this fault. If there are thumb valves or AAV's on that section of line you should check they are open or open and bleed them, its effectively the same result as having air in the top of a rad, seems like it gets hot on the pipes but not doing much on the emitter.

 I would find the code that give you the flow rate on the water circuits and check it in heating and hot water and compare them.

Cheers, yeah there's no AAVs or thumbvalves approaching the outdoor unit.

One of the first things I done was check the AAV on the outdoor but itself and purge some water through.  

The p1 error is often caused by an airlock but system is well bled in this case. 

Posted by: @2019ashp

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Cheers, yeah there's no AAVs or thumbvalves approaching the outdoor unit.

One of the first things I done was check the AAV on the outdoor but itself and purge some water through.  

The p1 error is often caused by an airlock but system is well bled in this case. 

 

 

I think @ashp-bobba was referring to a possible airlock in the DHW circuit, near the DHW tank itself.  As this is usually a high point in the DHW circuit there should be a bleed valve (automatic or manual) near the tank. 

Given your symptoms that does seem very plausible to me; @ashp-bobba does this for a living so should know!

Posted by: @jamespa

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Posted by: @2019ashp

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Cheers, yeah there's no AAVs or thumbvalves approaching the outdoor unit.

One of the first things I done was check the AAV on the outdoor but itself and purge some water through.  

The p1 error is often caused by an airlock but system is well bled in this case. 

 

 

I think @ashp-bobba was referring to a possible airlock in the DHW circuit, near the DHW tank itself.  As this is usually a high point in the DHW circuit there should be a bleed valve (automatic or manual) near the tank. 

Given your symptoms that does seem very plausible to me; @ashp-bobba does this for a living so should know!

 

Yes, I have seen "many times" where the indirect coil connections raise up but no air bleed, it only takes a small amount of air in the line to effect the flow rate.

Perhaps we can get a picture of the set up to see how it is? 

@jamespa Of course that's what he meant, I was half asleep 🙂  

I had look for a way of bleeding this last week but there doesn't seem to be a bleed valve on the grant monowave tank, nor an aav\thumbvalve on the plumbing circuit near the tank. Poorly designed IMO. 

But yes it does seem very, very plausible indeed with the symptoms. 

@2019ashp can you post a pic?

Posted by: @ashp-bobba

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Yes, I have seen "many times" where the indirect coil connections raise up but no air bleed, it only takes a small amount of air in the line to effect the flow rate.

Thats worrying, its like an obvious place for air to collect; why would you not put a bleed there (no need to answer that!)

@ashp-bobba thanks - I'm away for the day now but will do later, cheers