Evohome newbie questions: noise, losing comms, towel rad switching, balancing

[DorrisMancer]

I've had a reasonably large evohome installation (2 controllers, DHW, 23 rads, UPS2 pump, 3 towel rads) for a while now. I like the controllability but have a couple of questions:

I've got used to the HR92s whirring but not the whooshing sound that the water makes, which I presume is caused by the valves only opening a small amount(?) I've tried all 3 pump settings and selecting compensation on/off but without making a huge difference. All the pipework and boiler have been replaced but we had no whooshing noises before. Is this an Evohome "feechur"?

The controller keeps losing (and restoring) connection to the DHW thermostat. The distance is about 30ft and a couple of solid walls. Is this a common problem?

I put the towel rads on a separate circuit, with their valve controlled by a regular 7 day timer, but I'd like to use Evohome to control it. Can this be done as pure timer control (no temperature measurement) with a BDR91?

I'm struggling to accept that balancing is possible or necessary with such a dynamic system, where each rad opens unique amounts at unique times, so am tempted to fully open all the lockshield valves in the hope that it would reduce the whoosh noise. What have others done?

[bruce_miranda]

Did you need more than 12 individual schedules in your house. Most people think of their downstairs as separate rooms but unless you shut the doors on ever room, like you might/can do with bedrooms then you might as well have multiple rooms as a multi room zone.

Are your tower rails electric or on the CH? You can use a BDR91 to control an electric but beware of the current rating. You can buy the older relay units that went to higher current rating.

Balancing is required to ensure the temperature drop is maintained across the radiators.

[DorrisMancer]

It's a reasonably large house, parts of which are not used all the time. Also, the room layout is slightly unusual so there isn't as much heat transfer between rooms as might normally occur. I've got 20 unique zones and it's really useful to be able to set a low over-ride temperature on those that aren't being used, and then remove it when a room is needed.

The towel rails are on a separate CH circuit, with the zone valve controlled by a 7 day timer. Is it possible to control the zone valve with a BDR91 without any temperature sensing, so the evohome controller is just acting as a timer?

I'm still not convinced by the balancing argument. Why is a specific rad temperature differential needed (other than to get the specified heat output, which seems academic with this system)?
I can understand that the boiler return temp is important for condensing but can't get my head around how that can be maintained when HR92s are opening and closing by varying amounts at random times. It's just the same as the lockshield valves being adjusted all the time so how can balancing be important, except when all HR92s are calling for heat?

[bruce_miranda]

Evohome doesn't have a timer only zone.
Modern boilers have been designed for a 20C drop at each rad. We all think of balancing to ensure every rad gets its fair share of the flow. But balancing also ensures that the hot water entering the rad, stays in there long enough to lose its heat to ensure the return feed is as cold as possible.

[DorrisMancer]

Hmmm, it would be good to have a timer only mode added in the future.

OK, so the lockshield valves limit the maximum flow rate through each rad and therefore the water's heat loss in the rad and the temp differential across the rad. Heat loss varies directly with temperature excess (Newton's cooling law, I think) so will decrease as the air around the rad heats up - the rad output temperature will increase so "balancing" can only work at one room temperature. Have I get this wrong? If not, what room temp is typically used?

Sorry if this is all basic stuff, but for some reason I'm struggling to get my head around it.

[mtmcgavock]

Hmmm, it would be good to have a timer only mode added in the future.

OK, so the lockshield valves limit the maximum flow rate through each rad and therefore the water's heat loss in the rad and the temp differential across the rad. Heat loss varies directly with temperature excess (Newton's cooling law, I think) so will decrease as the air around the rad heats up - the rad output temperature will increase so "balancing" can only work at one room temperature. Have I get this wrong? If not, what room temp is typically used?

Sorry if this is all basic stuff, but for some reason I'm struggling to get my head around it.

The way I have my towel rails controlled by EvoHome is to have a BDR91 (wired to the Towel rail ZV) and a T87RF in one of the bathrooms. At the set points I have it set to a high temperature so that it doesn’t switch off - this gives you control in the Evohome as a timer. We actually find it really useful having the T87RF in the en suite as in summer we can turn it on when we get in the shower to 35oc and then turn it back off when we get out.

In winter I have the towel rails coming on with the hot water ZV, and also coming on with their own schedule and temp however we’ll not get into that 😂

[DorrisMancer]

Thanks, I'll copy that idea.

[filbert]

I've got used to the HR92s whirring but not the whooshing sound that the water makes, which I presume is caused by the valves only opening a small amount(?) I've tried all 3 pump settings and selecting compensation on/off but without making a huge difference. All the pipework and boiler have been replaced but we had no whooshing noises before. Is this an Evohome "feechur"?

I don't know about others but there's no whooshing sound from our system. The only change is the noise of the valves (which has been extensively discussed in another thread).

The only changes to the system were adding a new radiator and replacing all the TRVs before adding the HR92s - they were old and the system was being drained down to add the radiator, so it seemed to make sense.

[mylesm]

I've had a reasonably large evohome installation (2 controllers, DHW, 23 rads, UPS2 pump, 3 towel rads) for a while now. I like the controllability but have a couple of questions:

I've got used to the HR92s whirring but not the whooshing sound that the water makes, which I presume is caused by the valves only opening a small amount(?) I've tried all 3 pump settings and selecting compensation on/off but without making a huge difference. All the pipework and boiler have been replaced but we had no whooshing noises before. Is this an Evohome "feechur"?

Do you have an ABV or a modulating Pump you should not have water noises

[DorrisMancer]

There's an ABV and a Grundfos UPS2 pump, but you've made me wonder whether the pump is set to one of the fixed speeds or to the variable position - the instructions are less than clear so I need to investigate further.

[mtmcgavock]

There's an ABV and a Grundfos UPS2 pump, but you've made me wonder whether the pump is set to one of the fixed speeds or to the variable position - the instructions are less than clear so I need to investigate further.

If I remember correctly the III symbols are fixed speed and the gradient ones are the variable. Agreed the instructions aren’t great.

In regards to the noise, if all the HR92s are open (so calling for a demand) do you get the noise? This would rule out the bypass as it should be closed. I usually find the noise is the TRV body, we had a particular brand that would whistle when fully open.

[DorrisMancer]

The noise is definitely water whooshing through the valves as the HR92 opens. How do I check what mode the pump is in? (I can't find anything about it on google)

[mylesm]

The noise is definitely water whooshing through the valves as the HR92 opens. How do I check what mode the pump is in? (I can't find anything about it on google)

When you press the button for five seconds, the pump
will change from fixed-speed operation to proportional pressure
control

https://www.mcdonald-engineers.com/sites/mcdonald/files/grundfos-ups-2-.pdf

[dty]

Don’t use proportional control if you’ve got an ABV - they end up fighting each other.

[DorrisMancer]

https://www.mcdonald-engineers.com/s...fos-ups-2-.pdf

Thanks for this, it makes everything clear.

Don’t use proportional control if you’ve got an ABV - they end up fighting each other.

I can see the potential for this if the ABV is set too low but is it a problem in practice?