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Hi Andrew, I’m in the process of installing a lowloss header for my system, which will serve radiators upstairs and underfloor heating downstairs in a standard semidetached house. The radiator zone will have only 4 radiators. My question is, will I need to install a secondary pump for the radiator circuit after the lowloss header? I’m concerned that while the boiler pump is powerful enough to circulate through the radiators, the presence of the lowloss header might result in short circuiting within the header itself. Would this prevent adequate flow to the radiators, thus necessitating a secondary pump?

I fitted weather comp and I cant get mine to ramp up to 80c when hot water is on it just stays at the central heating temp, i have got a tado fitted as well so it might be somert to do with that?

Not sure if a real problem, but whilst the relay is switching there will briefly be no resistor in circuit and maybe the boiler could determine a fault? Better to leave the 12k in place all the time and just switch a 1k1 across it (e.g. in parallel) using the relay.

Great video andrew, I have an Ideal logic combi and I wish to add weather comp but when I do it seems to fire the boiler permanently at full chat. I dont want to miss out on the benefits but do you have any ideas of how to fix this? I have a EPH CP4 controller installed on opentherm but the boiler doesn't seem to modulate at all.

Love the volumiser position. We wanted to do similar on a job but space didn’t allow it. We used a smaller model (still 25ltr) but vertical fit only.

What king a dude makes a video while chewing food. Good lord people are gross.

Cracking video Andrew I’d love to see longer videos of the install process, it’s such nice change to see all the components accessible and “serviceable” as supposed to slung in with no thought to how to work on in the future.

Fufking Hungry was you mate Jesus christ

Peice of artwork Andrew ❤ love the bends.

Nice and tidy. Is that in a modern house with insulation upto building regs?

Very pleasing to anyone. Would love to see technical detail. Even longer will be not be ignored by many.

Exciting times for heat pump installers... less so for the owners in 5 years plus when the components need access for maintenance or repair! There is ALOT to go wrong shoehorned into that cupboard 🤷🏻‍♂️

Nice job like always 👍

Hi, I work for Worcester Bosch. Our 5800i, 7001i and 3400 (split) all have access to our MM100 module which allows you to mix a heating circuit using a blending valve 👍🏻. We also sell ready made pump groups, but it is more cost effective to build your own with an MM100 paired with an additional circulating pump and blending valve (from someone like ESBE).

We're renting a ground floor apartment in a house that also has a separate 1st floor apartment. We have exactly the same boiler and control 470 fitted to it. The main PCB is identical too and we've got two cables running: 1 mains power to L (brown) N (blue) E (g/y) + another one to the same brown block with connected terminals AF (brown) and inner OT (blue). I didn't realise it's for the external sensor and assumed it's for a room thermostat. There are identical wires in a box in our lounge but they're currently connected to other old wires. I measured voltage thinking it's for the 24V room thermostat connection but there's no voltage on them (or 0.6V). I checked the boiler PCB that looks exactly like yours and 3+4 (red) are also short. It's a complex boiler but what I would like to achieve is to have at least one room thermostat in the house that's set to desired temperature so we could further control on radiators room temperatures between both apartments. We want tap water to be always available in the tank that's around 40 degrees Celsius (or at least on day-night schedule). We don't have any solars or recuperation installations - only single zone CH covering both apartments, HW and a tank that holds it hot + possibly the external sensor which I can't find anywhere because can't follow the AF + OT cable to the other end. We normally dial the CH knob all the way to the left to disable CH for summer and se it to anything over 30 or 40 for winter to reenable CH. The CH is currently also set on a 3 time slots schedule that's not enough as we have a gap mid night when it gets too cold (a missing fourth one would probably partially solve our issue). Also, often there are nights when it gets too hot in the flat when the CH switches on on the set schedule thus wasting GAS and money making temps uncomfortably hot in the house. Please note I have already purchased a brand new VRT 350 thermostat thinking it would allow to more control of temperatures using schedule as opposed to simple desired temperature dial. Do I need another room thermostat e.g. Vaillant VR81 Remote Control Unit 20129323 or/and additional VR61/4 two zone wiring centre for use with VRC470 20139853 (probably an overkill for a single zone) for the installation or just hook up the VRT 350 I already have directly to the boiler's PCB then set in Installation section room temp control to Thermostat in order to be able to control CH in one apartment's room and where would I need to connect it = BUS + / - next to 7 and 8 or 4 and 4 thus replacing the existing red short wire (am presuming polarity doesn't matter although no voltage is currently present in both)? How would it work with the external sensor if it's installed as well and which would override the other in what situations? EDIT - FOUND THIS USEFUL DIAGRAM - 7+8+9 are 24V connectors that should control my new VRT 350 wired thermostat. 3 4 5 are 230V and not suitable for VRT 350. community . tado . com/en-gb/discussion/2883/installing-the-extension-kit-on-a-vaillant-ecotech-plus-831

Or you have the appliance on

Great vid Andrew. This came up on my feed just in time.

Hi Andrew, I just saw this old video of yours, as we're looking into MLCP for our heat pump jobs. Interesting comment about secondary returns: I recently heard that someone has experienced failures with MLCP on second returns, as the inner plastic layer blistered and the pipe became brittle. Have you heard of this? Also, what's the issue with copper in this situation?

Hi , Andre what is the par number for the new model you use ,thank you

Great idea with those shims. I was hoping to install my HP on the existing 900 mm wide concrete footpath. It has approx 2 degree fall. Do you think these kinds of shims could work to correct that much?

Hi Andrew, thank you for the explanations and help. If you had a primary boiler loop with one CCT. Is it ok the run a pump from the secondary circuit for a radiator circuit and the pump on a ufh manifold to run that circuit. With this is it necessary to include zone valves for each circuit as they are separated from the boiler pump. Thanks

Well explained andrew ps i cant download app from link on esbe site it says link not found can anybody help?

Thanks for the teachings! Helping me a lot with getting my head around design.

Any simplification in using a 4 port mixing valve like the viessmann undermount mixers have. i.e do they automatically control authority. Happy to be completely wrong.

Hi Andrew, great video. Currently going through Heat Geek and this is really helping so thank you. What’s the difference between a low loss header and a distribution header and what application would require one over the other. Hope that question makes sense. Thanks very much again.

Where are you ordering the esbe valves from? I was getting them from that german company on ebay but service was shocking the more i used them. Price was on point though.

Very helpful, thank you

IMI Hytools app is also very useful for pipe sizing to velocity I find. Definitely important to understand the longhand calculation forst though.

Thanks Andrew, really interested although im still slightly baffled by the mathematics (muppettry on my part)One query i have always had is regarding the stepping up in size from a distribution pipe to another. For example, you mentioned using a 35mm section being fed by 28mm port, i have always assumed the 28mm will only pass a maximum amount of fluid/heat through so therefore query the usefulness of the 35mm section. Perhaps you can direct me to where I can study the fundamentals of that ? Many thanks, John

Very interesting, thanks Andrew. Hope you are well 👍

Very informative video once again Andrew! I was confused at the start of the video as im used to using the velocity triangle to work out flow rates for fixed quanity of water through a fixed diameter of pipe ie Quanity over area x velocity but understand your equation converts from M2 to mm instead of converting it yourself.

Lots of content coming through Andrew thanks !

Thanks Andrew !

That helps so much andrew thankyou. Heard you mention this app a few times and so glad as you've made this easy from now on. Thanks again

How did you learn this low loss header tank is there a course

Excellent video, i understood the principle but its nice to see exactly what part of the valve this applies to, whether is the bore size or the rotating port as you've shown. Also if its a complete sized valve required or different inserts to fit inside of a body. It looks like the whole part is what you purchase is it? Is the brass part esbe too or just the motor black box?

Is it still possible to get the mixers with correct kv/kvs in a neat thermal jacket like the meiflow ones were. If this is a domestic set up, what's the kvs on these valves as an example.

Looks a good setup. Out of interest would this arrangement work on a single pipe system? Thanks

I love these morning bite size videos 👍

Another great video.

I would be interested in seeing the calculations from the header through to the valves and the actual method selecting those valves if you are able to at some time please. Thank you as always. Very helpful and informative presentations.

Very informative video, I was very lost with the kvs and authority references in previous videos! Thank you for laying it out so visually 👌

Do you have video of you doing the yearly maintenance drain bleed flush inspection on 100-w?

Hi Andrew. It’s Martin from Birmingham. I need your help please mate.

You are a lifesaver. I have been tearing my hair out trying to figure out how the DHW demand was signalled to my new B1HF Vitodens 100W. My previous system used a 4 channel Shelly controller to switch 3 heating zones and DHW, with a Y plan. As the Viessmann can do 4 pipe I replumbed for S plan, assuming that there would be a simple 230V input for 'traditional' stat/timer control. Alas, no! I was stunned. I figured the cylinder sensor was probably a simple thermistor (the NTC was a clue!) but spent ages trying to find the resistance values I'd need. Then I found your video. Thank you so much. I have a question - how about using your scheme with an actual thermistor, on the cylinder, to give both external control and the smart stuff from the boiler? Wouldn't give an accurate reading when there is no demand (mine reports 89.9°C with 1k across the sensor terminals), but would be accurate when the relay is off. My plan is to use an SMT thermistor connected to thin high temp wire (probably enamelled copper in high temp sleeving), attached to the end of the cylinder 'stat probe with Kapton tape, and taken back to the boiler, which contains the relay switching. As an extension to this, I may add a means of measuring the thermistor separately when there is no demand, using a Shelly Uni or similar. If I do I will update here with the outcome. Thanks again. You're a legend.

Hi Andrew. Can you cct about 4m away from the boiler? Not enough room at the boiler but can run the primary F&R to an area and put the cct in a hotpress?

So you are saying that those two valves are different? you have chosen a valve with a smaller orifice on the radiator circuit? Is this why you use those esbe valves instead of the viessmann mixers?

The cylinder is hugely overpriced. The 250lt costs £1,943.34 and when I pointed that out to the heat geeks their response was that “yet it takes sixty days to get hold of one”.

Legionella, you get them on commercial systems

Is there more info on this cylinder somewhere, or is it a prototype?