TRVs and Boiler Ignition

[sulley]

Dear All,

I currently have a conventional boiler with hot water tank, all open systems. CH control is provided by a Honeywell timer and a Honeywell wireless thermostat, which are entirely separate systems. Over the summer the wireless thermostat died and so I'm looking into replacing it with something a little more technologically advanced. What I have settled for is eq-3 MAX! system, which are wireless/digital TRVs which can be controlled by smartphone or computer from another continent if necessary.

My question is....... On my existing system, if the room temperature didn't decrease below the thermostat temperature, during the summer, then the boiler would not light up. With a TRV based setup, I am reliant on the water within the circuit reaching the required temperature, which as I see it, regardless of how hot our summers get, the boiler is going to light up multiple times a day! Is this correct and is this accepted?


Thanks,

Rob

 

[Dan Robinson]

What model Honeywell head do you have at the moment?


What boiler do you have?


The boiler will only have a single set temperature unless you can implement weather compensation.

That EQ system looks utter shyte.

Why not look at Honeywell's new Evo home system?

 

[sulley]

Thanks for your reply Dan, unfortunately I can't tell you what boiler and Honeywell head I have at present.

Do you have any experience of the eq3 system?

TBH it has been my experience that Honeywell's equipment does not match their reputation. The timer is prone to locking up after power cuts, requiring a power cycle to reset the system and the clock is incorrect by several minutes despite the fact it uses MSF. The wireless thermostat has huge amounts of hysteresis and is not capable of communicating a low battery warning to the user, hence when the battery goes flat, either the heating doesn't come on, or it stays on indefinitely. For these reasons and the cost premium which the Honeywell brand brings, I will not be looking at the Evo system.


Cheers

 

[sooey]

Get Told Robinson!

 

[Dan Robinson]

Funny how those EQ valves look remarkably familiar to the Peglar ones.... which do not have the greatest reputation. .


Can't vouch for the OP's problems with his Honeywell, but I see more of their stuff than he does and barring a few issues with a batch of bad sliders and another with iffy screens - all of which were dealt with rapidly, they have been pretty good.

Mind you I am having trouble deciphering the OP's actual question.

 

[sulley]

Well, if the EQ side of things doesn't work out then I still have the standard TRV heads that I could fit.

I apologise for my lack of clarity in my question, I'm not very familiar with plumbing terminology. Hopefully an example will help. Please ignore the hot water and imagine that temperatures day and night are 30degC.

At present my timer will turn the CH on at 7am, however because the wireless thermostat is set to 19degC, the boiler will not light up. This happens every day, and if it wasn't for the hot water my boiler would never light up.

If I get rid of the system thermostat and use TRVs then every morning the timer will turn on the CH at 7am. This signal is not interrupted by a system thermostat hence the boiler will be instructed to turn on. The water in the loop will be cold so the boiler will light up in order to heat up this water. None of this water will actually reach the rads because all of the TRVs are set to 19degc. Once the water in the loop heats up to the level dictated by the temperature control on the boiler, the boiler will turn off. This water will cool and the boiler will turn on again and bring the small volume of water in the loop up to temperature. So my boiler will cycle on and off all day long dispite the fact no heating is taking place.

I am just looking for confirmation if my understanding of the differences in behaviour of TRV based systems and those with a system thermostat is correct? I doubt my understanding because it occurs to me that this behaviour results in significant amount of wasted energy and wear on system components?


Thanks for taking the time to read this.

 

[Dan Robinson]

Yes - which is in breach of the building regs as you have no interlock for the boiler.

Which is why the Honeywell system is better at will not activate the boiler. Which would be a tremendous waste.

 

[Steelmasons]

You obviously have a controls issue? , with the wireless stat off then the boiler will not get a signal to fire due to the motorized valve not calling for heat , when the room temp drops below 19c (or whatever the temp on the wireless stat is set too) then the boiler will fire until stat is satisfied , hot water is controlled via a cylinder stat coupled with another motorised valve to switch boiler when needed.

I'm thinking you're on an advertising mission .

 

[sulley]

Thanks for your replies.

Dan, surely standard TRV based systems have this same issue with the lack of an interlock? Or are TRV systems also supplemented with an additional system thermostat?

Steelmasons, I'm not advertising anything, tbh I think Honeywell need to put Dan on the payroll!

 

[Dan Robinson]

All systems should have a thermostat - the TRV's supplement that.

You are looking at this the wrong way round.

 

[sulley]

Ah ha, now I understand, thank you.

If you google "eq-3 interlock", it becomes apparent that the lack of a boiler interlock is a well known 'weak point'.... or 'deal breaker' as it is in my case.

Dan, have you ever heard of the Honeywell Evo system? It looks pretty good, you should really read up on it, Honeywell isn't as unreliable as you think!

 

[picasso]

The baxi solo HE lets you have a fully trv..ed system with no room stat, the central heating is controlled by the boiler flow switch so unless you got this boiler your going to have to use a room stat.

 

[Dan Robinson]

It is still a Baxi though .


Sulley - I have been accused of knowing my way around the Evo system .

I have rather a lot of it at home myself.

 

[mrmouse]

Sorry to revive this old thread....

i've also been looking at the eQ-3 - mainly for the open window control, to shut a rad off when a window is opened. I have seen one of these (although a Honeywell) in use in Germany. Honeywell don't appear to do that model here, or perhaps they've stopped marketing it.

On the subject of EvoHome, it's ridiculously expensive. That would never pay back for me. eQ-3 however, is much more affordable.

On the subject of the require interlock in the UK, I am curious how the German systems work. They don't have room/house thermostats. They do have weather compensation (and have had for years) which I also have. But no room thermostat. I have a weather compensating Vaillant system, and it seems to have logic built in to put the boiler to sleep if the return temp on the flow is the same as (or probably close to) the flow set-point. So if it detects no heat loss in the circuit, it shuts off the boiler. It also uses the outside temp to set anti-cycle time on the boiler, so as it warms up outside it runs the boiler and pump (it's a comb, so internal pump) less often. I have the controller set to thermostat mode (and it also uses internal temp to adjust flow) but it can be set to "German" mode where it ignores the room temp. With my system, I suspect the eQ-3 Max heads all over the house would be fine even when the Vaillant controller is in "German" mode, or in Modulating mode where it will always run ever when room temp has been reached - it simply lowers the flow temp to keep the house warm.

Any experience out there on the difference between the UK and continental hearing systems? Opinions? I'm just interested to hear.