New Evohome plumbing issues

[sandyman]

sorry joining this one late - seems like you've solved your "cold rads" problem , but if it is air, another option is fitting automated air bleeds at multiple locations (requires drain down of course). my plumbing has a lot of up/down/sideways runs and was very prone to air, but my plumber fitted some (what he referred to as "seriously high end") air bleeders inline on the primaries, better than the 15 quid jobs with the red/black plastic screw (although do have one of those in the AC), and that sorted it.

regarding your noise when only 1 particular rad is slightly open and the rest shut, I had a similar issue (and i have bidir honeywell trv's like you). not hammer in my case, but a resonance noise - the pipes musically vibrating (very loud) - the slightly open trv gap acts as a reed, the pipes are the resonance chamber, you've made yourself a wind (water!) instrument. anyway the point is that i fixed it by introducing a variable speed circulation pump - I've used a grundfos alpha. when only 1 rad is open it drops down to a very low pump power so the resonance standing wave can't form.
IMO it would be even better if evohome/opentherm could talk to the pump about how much power was needed, but it seems to work reasonably well - if your flow/balancing is up to scratch, the pump figures out the right level itself.

[Tempted]

sorry joining this one late - seems like you've solved your "cold rads" problem , but if it is air, another option is fitting automated air bleeds at multiple locations (requires drain down of course). my plumbing has a lot of up/down/sideways runs and was very prone to air, but my plumber fitted some (what he referred to as "seriously high end") air bleeders inline on the primaries, better than the 15 quid jobs with the red/black plastic screw (although do have one of those in the AC), and that sorted it.

regarding your noise when only 1 particular rad is slightly open and the rest shut, I had a similar issue (and i have bidir honeywell trv's like you). not hammer in my case, but a resonance noise - the pipes musically vibrating (very loud) - the slightly open trv gap acts as a reed, the pipes are the resonance chamber, you've made yourself a wind (water!) instrument. anyway the point is that i fixed it by introducing a variable speed circulation pump - I've used a grundfos alpha. when only 1 rad is open it drops down to a very low pump power so the resonance standing wave can't form.
IMO it would be even better if evohome/opentherm could talk to the pump about how much power was needed, but it seems to work reasonably well - if your flow/balancing is up to scratch, the pump figures out the right level itself.

Interesting with the variable pump. My issue is that the system as a whole has cost nearly £8k and SWMBO already has a poor opinion of the plumber for it not being perfect (when we all know issues like those I've had are quitecommon and he wasn't the original architect...!). Spending more on pumps and fitting may be a hard sell . My plumber would likely think I am mad for wanting to cut the inbuilt pump out of the equation when it is brand new - how would you circumvent the standard one in a system like this? Pardon my ignorance, I am an IT geek by trade and so plumbing isn't second nature...!

[sandyman]

I think you will find many on here are IT geeks - I certainly am! I do big networks for a living. plumbing is just wet packets :-).

I don't know any details of your system but if it has a circulation pump that looks like a standard CH pump builtin somewhere, then you ought to be able to replace it with another standard CH circulation pump. The variable speed grundfos alpha ones are an exact fit replacement for a "standard" pump, they just have a variable speed brain , with flow/pressure sensors and feedback, rather than the simple I-II-III lever of old. if you can find your pump and it does have a I-II-III setting lever , try manually turning it down to see if that alleviates noise when running with just 1 rad open. you will need to turn it back up when you want full circulation to all rads. If yes, then the variable speed pump may well help you.

the alpha pump is about 100 quid and if there are standard isolators fitted either side as there ought to be , its not a long or complicated job to change.

oh and regarding your outlay - thats figure is not uncommon (mine similar) and regarding SWMBO - its taken me a year of tweaking before I'm fully happy its WAF friendly. the issue I have found is getting hold of a really good Heating Engineer, not just a plumber. The skills to fit bathrooms/kitchen sinks/tiling, are not the same as those to do a really optimal heating system. I've read some posts on here from other people who really really understand the physics. you may just have to learning the heat transfer physics and engineering yourself..

[DBMandrake]

I think you will find many on here are IT geeks - I certainly am! I do big networks for a living. plumbing is just wet packets :-).

Same here ;-)

I don't know any details of your system but if it has a circulation pump that looks like a standard CH pump builtin somewhere, then you ought to be able to replace it with another standard CH circulation pump. The variable speed grundfos alpha ones are an exact fit replacement for a "standard" pump, they just have a variable speed brain , with flow/pressure sensors and feedback, rather than the simple I-II-III lever of old.

I have a Grundfos UPS2 15-50/60 which whist not as fancy as the Alpha, has both three fixed speeds and a variable speed mode with three different slopes, and guess what ? There are no pressure sensors at all, as taking the pump head off the base will show.... As far as I know these variable speed pumps don't directly measure the pressure with a pressure sensor, but rather infer it through measuring the torque/rpm curve of the motor.

On a three phase AC motor (as these electronically controlled ones almost certainly are) its quite easy to both measure the RPM and the instantaneous torque output since the motor will draw more current the more it is loaded. From that and the design of the impeller a pretty accurate estimate of both volume flow and output pressure can be made electronically. Very clever.

On the down side, I can't use the variable speed mode on mine because the microbore piping to many of my radiators are perceived as restriction by the pump and it just will not speed up fast enough. (Even with all radiators on in the fastest variable speed mode it still runs slower than the slowest fixed speed mode, which is too slow for the flow requirements for my boiler, which was not designed with a variable speed pump in mind)

You also have to be careful about unintended interactions between variable speed pumps and automatic bypass valves - an automatic bypass valve set too low confuses a variable speed pump because as soon as the pressure it is set to is reached it starts to open and the flow restriction reduces, the variable speed pump treats this like an opening radiator and speeds up, this opens the ABV valve even further and so on. Soon the pump is running at full speed trying to satisfy the flow of a fully open ABV even when no radiators are open. (It is a runaway condition)

So if there is an ABV valve fitted in a system with a variable speed pump it should be adjusted to maximum (typically 0.6 bars) so that it doesn't cause the pump to run too fast all the time, and in theory there shouldn't be an ABV fitted at all with a variable speed pump, as long as the boiler is designed for use with a variable speed pump.

[Tempted]

I think you will find many on here are IT geeks - I certainly am! I do big networks for a living. plumbing is just wet packets :-).

Evohome is certainly a gadget lover's dream!

I don't know any details of your system but if it has a circulation pump that looks like a standard CH pump builtin somewhere, then you ought to be able to replace it with another standard CH circulation pump. The variable speed grundfos alpha ones are an exact fit replacement for a "standard" pump, they just have a variable speed brain , with flow/pressure sensors and feedback, rather than the simple I-II-III lever of old. if you can find your pump and it does have a I-II-III setting lever , try manually turning it down to see if that alleviates noise when running with just 1 rad open. you will need to turn it back up when you want full circulation to all rads. If yes, then the variable speed pump may well help you.

the alpha pump is about 100 quid and if there are standard isolators fitted either side as there ought to be , its not a long or complicated job to change.

Yeah you're right, I should be able to simulate the issue without having to wait for it to occur naturally. TBF, since I altered the ABV settings, it hasn't happened again, but it could be that the exact circumstances needed haven't either.

oh and regarding your outlay - thats figure is not uncommon (mine similar) and regarding SWMBO - its taken me a year of tweaking before I'm fully happy its WAF friendly. the issue I have found is getting hold of a really good Heating Engineer, not just a plumber. The skills to fit bathrooms/kitchen sinks/tiling, are not the same as those to do a really optimal heating system. I've read some posts on here from other people who really really understand the physics. you may just have to learning the heat transfer physics and engineering yourself..

This is a complete understatement. I had great difficulty even getting someone to fit my Evohome bits and I'm not 100% happy that he did as good a job as I'd have done myself had I had the time to educate myself with the skills needed. I specced my entire system and the only experience I had was from reading forums. My plumber knows about pipes, flows, returns etc, but he didn't have much of an opinion on boilers or cylinders. Maybe I was naive to think it should work that way. If I did it again, I may have been tempted to get a heating engineer to spec the whole system instead of trying to muddle through it myself!

My issue came down to money. I don't think anyone who goes for the Evohome could be considered a penny pincher, but when you're spending the kind of money talked about above, SWMBO can't be criticised for asking questions when you've had two professional electricians round to fit your equipment and still end up re-doing some of it yourself because you're OCD...! Paying the kind of money needed for a heating engineer to design your system would probably have put this out of reach for us, although I dare say it would have been better designed.

[sandyman]

I have a Grundfos UPS2 15-50/60 which whist not as fancy as the Alpha, has both three fixed speeds and a variable speed mode with three different slopes, and guess what ? There are no pressure sensors at all, as taking the pump head off the base will show.... As far as I know these variable speed pumps don't directly measure the pressure with a pressure sensor, but rather infer it through measuring the torque/rpm curve of the motor.

seems I over-read the specs inferring sensors that weren't there, and i defer to your superior knowledge on the current / torque thing. one question - how can it be 3 phase (when fed from uk household 230v?).

So if there is an ABV valve fitted in a system with a variable speed pump it should be adjusted to maximum (typically 0.6 bars) so that it doesn't cause the pump to run too fast all the time, and in theory there shouldn't be an ABV fitted at all with a variable speed pump, as long as the boiler is designed for use with a variable speed pump.

however if the boiler heat exchanger is in a hot condition and all zones quickly shut down, the pump needs to overrun to cool it, so the boiler switches the pump on. in that case surely you have to have an ABV regardless of whether your pump is variable speed or not? I have seen my system do this once or twice.

[sandyman]

This is a complete understatement. I had great difficulty even getting someone to fit my Evohome bits and I'm not 100% happy that he did as good a job as I'd have done myself had I had the time to educate myself with the skills needed. I specced my entire system and the only experience I had was from reading forums. My plumber knows about pipes, flows, returns etc, but he didn't have much of an opinion on boilers or cylinders. Maybe I was naive to think it should work that way. If I did it again, I may have been tempted to get a heating engineer to spec the whole system instead of trying to muddle through it myself!

My issue came down to money. I don't think anyone who goes for the Evohome could be considered a penny pincher, but when you're spending the kind of money talked about above, SWMBO can't be criticised for asking questions when you've had two professional electricians round to fit your equipment and still end up re-doing some of it yourself because you're OCD...! Paying the kind of money needed for a heating engineer to design your system would probably have put this out of reach for us, although I dare say it would have been better designed.

I wish in the end I'd had a "bog standard"contract day-rate plumber do all the wet/pipe work, and the rest of the design myself, but I didn't have the time so I picked 3 from the honeywell connected home specialists list, got all of them in , and picked the ones that I thought understood what I wanted best (who were not the cheapest). problem is you can call yourself a "plumbing and heating engineer" on your van and there is no real difference between that and a plumber with a corgi/gas safe, and the honeywell thing I think just means they have been on the course. Don't get me started on people using the term engineer for "man who fixes domestic appliances". Grr...

I used to have an older guy do my work and he was an IPHE who specialised in domestic heating - he wouldn't do a sink unless part of a larger job - but he's retired now. I agree though if you wanted to get someone who does this professionally for commercial systems it would price itself out.
(for the same reason as you wouldn't afford to pay me to setup your home network, although it would be proof to anyone apart from NSA/GCHQ/PLA, sorry wandering OT)