3-point only really consumes energy when the motor is moving in either direction, a 2-point is similar, but the switched live operates a internal relay to change the motor direction (powered by the permanent live), so the relay coil adds a small load when energised, but is fairly insignificant - I tend to use 3-point control (NO/NC) with the Sintesi’s. As mentioned, the main thing is to choose a valve with a sufficiently high Kvs (can’t really be too high for a diverter!) to ensure you have sufficient pump head - which maybe less of an issue for small heat pumps/systems and/or if you have a buffer/LLH and secondary pumping, but all resistance consumes energy £££!
PS, had sticking problems with the Honeywell VCs in district heating HIU’s, although to be fair, the problem was probably dirty primary water, so maybe less likely is a clean domestic heat pump system!
Thanks, so I really don’t know what to buy now. So basically all valves does not consume power if the position is fixed ? So then what’s the benefit of e.g. spring valve and 2/3 pont controlled ? I have 1" pipping so there should be no issue with this pressure lost I believe but try to find one with high Kv. But I don’t have buffer tank and secondary pump so don’t know what would be sufficient in this case. Are there valves which consumes energy all the time no matter of the position ? These I would like to exclude.
I too have been struggling finding a 3way valve for both the DHW and my floor heating. I finally chose an amazon 35-40€ valve, and made the missing parts to make it work.
In terms of valve Kvs, something around 10-12 may be sufficient for your system (higher is better), but ideally you need to know/calculate the pressure drop of the system index circuit (the one with the most resistance) and the total system flow rate to determine your pump duty and redesign if necessary. System design is important for heat pumps - if in doubt pay someone, it maybe cheaper in the long run - sometimes if you buy cheap, you buy twice!
Yes I know But I guess some simple valve is fine. It’s 1" and as I’ve said I have some pressure lost elsewhere but right after a pump (this is external pump) there is no issue… I have very simple connection of the HP to the system (radiators, no buffer, etc…) and SCOP around 3.5 which is not the best but I can live with it. For type 21 rads it sounds pretty reasonable.
Sorry, but I not sure you understand what I’m trying to explain about the effect of valve Kvs - but I’m not always be the best at trying to explain things for everyone, maybe someone else can help explain things better! However, as mentioned, without knowing your system specifics, a DN25 (1" or 28mm) diverter with a 10-12 Kvs or higher may be ok (depending on pump), either spring return or 2/3-point, spend as much or as little as you wish. But it maybe worth doing bit more homework on system pressure drop/pump duty, or get some professional help if need be. Good luck with it all.
Actually it’s been working just fine for a few months now. I don’t have much to conclude on the reliability just yet.
However, I guess it’s probably not that sturdy in the long term. Nonetheless, from my past experience with UFH, I’ve had to change the 3 way valve due to muddy water (the previous boiler wasn’t that good at driving the UFH). Therefore, I guess 5 years for that price is largely acceptable.
Reliability wise, it’s not leaking (yet!), I guess that’s a good point for that price point…
Also, the worst part of the setup is to wire the UFH 3 way to fit the expected opening/closing duration required by the EHS.
Yeah, that one has opening time 15s if I’m not wrong. How did you wire it to fulfill this ? For my pump I can select 60s, 90s and 150s so this is way longer so not sure what would happen if I’d connect this valve. I thought it does not matter how fast the valve opens but I’m not expert in this field.
The trick was to power the NE555 from the L1/L2/N line to avoid yet another plug power adapter…
Also, it’s related to speed, but more importantly, it’s a matter of matching the proportionnal opening given an operation time.
[EDIT] After rereading the topic, I just saw I mixed up topics here. The fact that the valve open faster/slower is not a problem for DHW. it’s only a problem for UFH 3 way valve. for which the circuit describe above is meant to.
This is nice schematics. Yes, this can be useful for UFH and mixing valves but for my need and DHW I really don’t care about opening times so the simple 3-way valve should do the trick. Maybe I will buy a cheap one and I will be good to go. And maybe it won’t work properly because the HP will complain as this is dumbest pump I’ve ever seen It even complains if you keep the pump running when the compressor is off
Further to above and hopefully fill in the blanks I left…
In a sealed/closed circuit the system height (static head) can be ignored when sizing the circulating pump, it only has to overcome the resistance (pressure drop) of the pipework etc.
A typical system has many parallel paths for the water to flow to each rad/ufh circuit, these circuits vary in length and heating load (flow rate) and the circulating water will take the path of least resistance.
When sizing the system pump we need to know the resistance (pressure drop) of the index circuit, this is the circuit with the highest resistance at its design flow rate, which is often (but not always) the circuit with the longest pipe run. Circuit pressure drop is accumulative, so you need to add up the resistance of all the flow & return pipework, valves, heat meters, rads and heat exchangers etc between the pump and the end of the circuit, plus a margin for error.
The pump will need to be sized to overcome the resistance of the index circuit whilst circulating the TOTAL system flow rate - for example a 7kW system at 5 degree dT with a 30 kPa index circuit pressure drop would have a pump duty of around 20 l/mim @ 30 kPa (~3m). So that when all the circuits are balanced they should receive their design flow rate.
With regard to system height (static head), the system cold fill pressure would typically be around 1.5bar (15m head) for most domestic systems, which is more than adequate to ensure the highest pipework/rads etc are filled with water and pressurised. The system expansion vessel gas pressure should be set (whilst isolated from system) to, or slightly less than, the system cold fill pressure, this will ensure the system pressure doesn’t drop off when cold or blow off when hot, assuming the EV is sized correctly!
Hope that helps when considering diverter valve selection on an open circuit system without buffer/LLH and just the primary pump, especially on larger systems over ~7kW.
Thanks for explanation. I have radiators where from the main pipe 28mm it splits the flow to 3 smaller circuits with pipes 22mm. I have only one primary pump on the main pipe (HP does not have internal pump). This is simplest connection possible and somehow it works fine. All rads are warm an no issue. With grundfos alpha 25-40 my max. flow was 16.8 l/m which looks like not sufficient. I switched to 25-60 and it’s tad better up to 22l/m. I’ve expected more but I guess there is some pressure lost somewhere on piping. E.g. I have Total Filter 1" so probably here and probably those 3 circuits have higher pressure loss, I don’t know. In any case it works pretty fine. I have no buffer, nothing.
But now I want to connect DHW tank and also want to use simplest approach possible. So my plan is just a 3-way diverted valve (not mixing valve so I don’t care about opening time, etc.) so just debating one with 2 cables so when it’s under load it opens DHW and without current it returns back to deliver heat to radiators.
Would this work ? Any drawbacks or potential issues with this setup ? I know there are maybe better ways but I would use simplest setup since my skills are limited
Yes you just need a simple 3 port diverter valve - a diverter is just changing the total flow direction and ideally wants have a low resistance (higher Kvs) to help minimise pumping effort/size/cost.
I personally like to use the Sintesi diverter valves with 3-point control (2 switched lives, NC-NO), it’s a well made simple full bore high Kvs valve, covers a wide range of heat pump sizes and doesn’t cost a fortune - it also doesn’t slam shut like some spring return valves, which can induce water hammer through the cylinder coil etc and would generally avoid the rubber ball Honeywell type valves, but they seem to work ok for a lot of people!
Your heat pump isn’t at the big end of the scale, so you may have a bit more flexibility on diverter Kvs. But comparing the various valves discussed above the more restrictive valve could add an additional ~5-10 kPa (05-1m head) for systems between 8-12kW, which when you also start to add mag filters, heat meters and less than ideal pipework etc into the mix, the system pressure drop can start to add up, so simply choosing less restrictive diverter can be an easy win, especially if the pump duty is sailing a bit too close to the wind!
Yeah, thanks. I will look at that Sintesi but I’m struggle to find it. Would you mind to post a link on amazon or some EU store where I can buy it ? I need DIN25 (1") valve.
How would you compare these two valves, what benefits Sintesi gives more ?
It’s appx 2.5x more expensive that IBO but IBO has also pretty good KVs. What I don’t know if the IBO one consumes energy only when it’s running the motor or also in standby state. I guess it has 7W when running but in standby it could be much less ? Spring ones consumes energy only when motor is running.
I have no experience with that valve and I like to stick to what I know works well/reliable and don’t consider the Sintesi that expensive in the big scheme of things, but each to their own!
You could get lucky with a cheapo from china, but it might end up being made from knock off camembert
