I’m seeing a similar thing in one room only. Set point gets set to 35 during heat up then resets once the set point time is reached. Doesn’t happen every time but has at least 3 times now. Have reset the hr92 in the offending room to see if that helps... will report back.
Evohome firmware 02.00.19.31 Beta Trial - Exclusive for Automated Home Members
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Originally posted by Andy the Minion View PostIn a previous life I came from the boiler industry and have been used to setting the pump to run constantly in opentherm or otc systems. The HR92 stay open when the boiler is off and my logic is this allows the heat that may have be left standing in a pipe run to be distributed evenly within the house and the water comes down to a nice steady return temperature ready for the next burner on cycle. I have no actual evidence which is better mind, just a gut feeling.
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Originally posted by mtmcgavock View PostDon't think we've got any chance of getting thatResideo employee. Comments are personal, and likely to get a hard stare from Rameses
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Originally posted by paulockenden View PostIdeally the outside temp used would be a 'feels like' temperature, as that includes wind chill (which chills houses as much as it chills people). Much better than just using a normal 'weather station' type value.Resideo employee. Comments are personal, and likely to get a hard stare from Rameses
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Originally posted by mtmcgavock View PostYes but with OT theres a demand, so the pump is pumping somewhere - on a TPI cycle the BDR91 unlatches and closes the Heating MV and therefore it's just pumping round the bypass. So all the useable heat is just going round the bypass circuit.Resideo employee. Comments are personal, and likely to get a hard stare from Rameses
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Originally posted by Andy the Minion View PostYep true that overruled the HR92 is open statement, I'm not a big fan of on/off valves unless they are completely necessary (I know, sometimes they are)Resideo employee. Comments are personal, and likely to get a hard stare from Rameses
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Originally posted by Andy the Minion View PostIn a previous life I came from the boiler industry and have been used to setting the pump to run constantly in opentherm or otc systems. The HR92 stay open when the boiler is off and my logic is this allows the heat that may have be left standing in a pipe run to be distributed evenly within the house and the water comes down to a nice steady return temperature ready for the next burner on cycle. I have no actual evidence which is better mind, just a gut feeling.
It also helps prevent kettling in the boiler heat exchanger as it's not forcing the entire flow to go through the ABV every few minutes. (Removing the boilers heatsink in the process)
However to make this work properly on a system like mine with a heating zone valve (and address the issue mtmcgavock raises about the heating zone valve closing) I have a nice little wiring hack for my heating zone valve that I've been using for the last couple of years:
In short, if the hot water relay is on, (hot water reheat) the heating zone valve follows the on/off status of the heating relay.
However when the hot water relay is off the heating zone valve will ignore the heating relay and stay on so long as the pump is running. (Even during overrun)
This allows water to continue circulating continuously through radiators throughout the TPI cycle except when there is a hot water reheat in progress which might otherwise cause the radiators to go over temperature. When a hot water reheat is in progress the heating zone valve will follow normal TPI control to reduce heat transfer to the radiators.Last edited by DBMandrake; 3 April 2020, 07:36 PM.
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Originally posted by Andy the Minion View PostSteve, The others are commenting on the process of adding the service company for diagnostics, rather than requesting the firmware. The second is completely optional.
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Years ago, @DBMandrake came up with the brilliant idea to have the CH Valve open with the pump, rather than be controlled by Evohome. Best mod I made. It allows the CH Valve to open and close and hence not seize but more importantly it circulates the heat through the loop in pump over run mode. it also takes care of boiler frost protection too. I love the idea, so simple and effective.
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Originally posted by SteveP View PostAndy - sounds intriguing, can you elucidate? is there more to this algorithm than just what the temperature reads on the controller?Resideo employee. Comments are personal, and likely to get a hard stare from Rameses
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Originally posted by DBMandrake View PostThis is exactly my thinking as well. If the pump keeps stopping every few minutes hot water sits losing heat in pipework without reaching the radiators, especially with a low TPI duty cycle where the one or two minutes on time might not even be enough for the slug of hot water to reach some radiators. Continous flow through the radiators while the boiler flame cycles on and off gives a more even distribution of heat around the system.
It also helps prevent kettling in the boiler heat exchanger as it's not forcing the entire flow to go through the ABV every few minutes. (Removing the boilers heatsink in the process)
However to make this work properly on a system like mine with a heating zone valve (and address the issue mtmcgavock raises about the heating zone valve closing) I have a nice little wiring hack for my heating zone valve that I've been using for the last couple of years:
In short, if the hot water relay is on, (hot water reheat) the heating zone valve follows the on/off status of the heating relay.
However when the hot water relay is off the heating zone valve will ignore the heating relay and stay on so long as the pump is running. (Even during overrun)
This allows water to continue circulating continuously through radiators throughout the TPI cycle except when there is a hot water reheat in progress which might otherwise cause the radiators to go over temperature. When a hot water reheat is in progress the heating zone valve will follow normal TPI control to reduce heat transfer to the radiators.
It is something i'm going to have to implement though, i'm just getting a lot of wasted heat - my rad in my garage acts as a bypass so all the heat is going into there.
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Originally posted by mtmcgavock View PostSurely with this though in the summer you get heat into any rads with no HR92s?
You're right though - if you did have a bypass radiator then at the end of a hot water reheat cycle in summer a small amount of latent heat from the boiler heat exchanger would be dumped into that cold bypass radiator, however that's a good thing for the boiler, and it would barely be enough to make the radiator luke warm and would only occur once at the end of each hot water reheat cycle. (The heating zone valve would stay closed until the hot water zone valve closed and the boiler stopped firing - then it would open when there was only latent heat remaining)
When I did have a bypass radiator it barely warmed at all from the heat dump due to the relatively high thermal mass of the radiator vs boiler heat exchanger.
Now that I have all HR92 controlled radiators I rely on a one minute hot water overrun to allow latent heat to dissipate at the end of the hot water reheat cycle.
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Originally posted by DBMandrake View PostThis is exactly my thinking as well. If the pump keeps stopping every few minutes hot water sits losing heat in pipework without reaching the radiators, especially with a low TPI duty cycle where the one or two minutes on time might not even be enough for the slug of hot water to reach some radiators. Continous flow through the radiators while the boiler flame cycles on and off gives a more even distribution of heat around the system.
It also helps prevent kettling in the boiler heat exchanger as it's not forcing the entire flow to go through the ABV every few minutes. (Removing the boilers heatsink in the process)
However to make this work properly on a system like mine with a heating zone valve (and address the issue mtmcgavock raises about the heating zone valve closing) I have a nice little wiring hack for my heating zone valve that I've been using for the last couple of years:
In short, if the hot water relay is on, (hot water reheat) the heating zone valve follows the on/off status of the heating relay.
However when the hot water relay is off the heating zone valve will ignore the heating relay and stay on so long as the pump is running. (Even during overrun)
This allows water to continue circulating continuously through radiators throughout the TPI cycle except when there is a hot water reheat in progress which might otherwise cause the radiators to go over temperature. When a hot water reheat is in progress the heating zone valve will follow normal TPI control to reduce heat transfer to the radiators.Resideo employee. Comments are personal, and likely to get a hard stare from Rameses
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