John Carroll

Can the same temperature compensation models be used for the above, ie a house with Radiator heating only and another house with UFH heating only. In the attached Vaillant WC Curves, one might use Curve 1.8 with radiator heating where a rad temperature of 70C might be required at -5C but use say Curve 0.6 with UFH heating where a UFH flow temperature of 42C might be required at -5C. Can some one post their UFH WC curves please. Vaillant Weather Curve.docx

Well, any flowrate up to ~ 5 LPM with both rad valves fully open, should not be problematic, IMO. Assuming a flowtemp of 42C then the rad output will be 33.4% of a T50 with a dT of 0.95C, if it is running with a dT of 5C then its output is 29.4% of a T50 with a flowrate of 0.84LPM. If it is running with noisy operation at say 7.0LPM then its output is 33.7% of a T50 with a dT of only 0.68C. These numbers are all based on a 1.0kw, T50 rad.

Have you smart radiator valves controlled by Evohome or such? Check circ pump settings and post its make/model/mode/settings and flowrate if it displays it. Check UFH manifold meter settings (throttled etc) and flowrates. Does one circ pump serve the rads and the UFH? Where is the expansion vessel located?.

https://www.wolseley.co.uk/product/neomitis-2-port-zone-valve-22mm/?srsltid=AfmBOoqv_ENIV53nUqWT0o_kPleTlp7Vrj29abrEn4EMV9R9BhMx7LT7

This might be of interest as it shows the effect of the cold feed teed in both before and after the pump, I just calculated the pressures at 4 or 5 points in a system with a loop of pipe, but doesn't matter, the differential pressure through any system is still the pump head. Point of No Pressure Change M Rev0.xlsx

That's the valve, below, operates like any 2 port valve, you can see the lever in the Auto position, on the end to the left, when you pull on this you should feel a fairly stiff resistance while pulling it across to the right, when its almost fully over, just push the lever up and let it move back towards the left, the lever will then latch in (up) and keep the valve open, but, as stated above, will not operate the micro switch as its only latched open when draining or refilling the system and you don't want your boiler, that you forgot to switch off!, firing up with no water in it. When energised open the valve will move fully across and engage the micro switch to fire the boiler. If the lever feels loose and floppy without any resistance when pulling across when NOT energised then the actuator is kaput and needs renewing. Another feature of these valves is that if you have it manually latched open say when refilling the system and its then energised, when its deenergised again the valve will close automatically as the lever will have fallen down, out of its latch, when motorised fully across.

A boiler flowrate of 0.6m3/hr, 10LPM, with a dT of 10C gives a output of, 10*60*10/860, 6.98kw, with rad(s) outputs of ~ 21% (flow/return, 40C/30C) of their T50 rating. I really can't see any reason for the system to be pulling in air, the distance from the F&E cistern level to the pump is 3.7M and because the vent & cold feed are teed in before the pump suction then the pump discharge pressure will be 6.7M (@3.0M pump head) and irrespective of the pump head, the lowest pressure in any part of that system has to be 3.7M or greater. Try and do that glass test before you go on holiday (and enjoy), IF the vent is pulling in air continuously then very very strange, the obvious one is wrong pump orientation but we know that the pump is pumping upwards. Apart from that, air ingress, over time, can occur through pump gaskets or non barrier "plastic" pipework etc.

Thats a nice circ pump, I've installed a few of them in my relations systems. They also show the flowrate in m3/hr, you might post this while running in CC2 (Fixed speed2) @ 3.0M on CH, you might expect to see ~ 0.7/0.8m3/hr, the pump also displays the power in watts (W), please post this as well, How many rads??, Not sure what you mean by the pipe calcs, for every meter change in level in a 22mm copper pipe, 0.32L of water has either to be added to it or removed from it?, IMO. Do you leave the shut off caps on the two (automatic?) vents open allways and do you see or hear any air venting from them?, if you don't leave them open, why not?.

Can you post a photo of the pump&pipework as is now? How far is the boiler (elevation wise) below the pump? You might do that glass test again but in a slightly different way which should prove whether the vent is continually drawing in air or not. With the pump running at ~ 3M, only then immerse the vent end in the glass of water and see does the level remain the same. 22mm of copper pipe has a ID of 20.2mm so should have a capacity of 0.32L/M, a " 1 pint" glass say 0.5L, if all the water was sucked out of it on pump start up then the level in the vent must have dropped by 1.6M, or 0.8MM if a 1/2 pint glass, I've read that the level in a normal system falls by ~ 10mm in both the vent&cold feed with a running pump.

The photo shows either a mid position valve or a diverter valve (with the adjustable spanner), why/how is the F&E cistern only feeding the CH circuit, its teed into the pump inlet?, and whats the other pipe for?

Are the vent and cold feed dedicated only as a vent and cold feed?, ie, there are no returns (or flows!) teed in anywhere to either of them. My Vent from the boiler on the ground floor right up to the HW cylinder (on the landing) have all the flows teed off from it.

There should be a arrow on the filter body as well, check this is also pointing UP. Is the filter clean?

So, the magnaclean, cold feed & vent are all very close to the pump inlet (suction end) and the arrow on the pump body is definitely pointing UP??

Yes, something like that. Re your existing set up as per your line drawing, can you give a estimate of the distances starting at the vent.... vent to cold feed, cold feed to filter and filter to pump inlet.

Yes and thats why the distsnce between the cold feed and the vent should be kept as little as possible, < 150mm so no pressure loss between the two. Its illogical allright but I have seen systems like yours that display the same problems "cured" by converting to my type, with the two combined as close to the F&E cistern as possible, needs a bit of plumbing though.

That looks fine, flow from the boiler outlet (hot) with Vent then Cold feed then Pump?. Sometimes the cold feed where its teed into the flow can get partially blocked and cause problems, can you watch the vent for pump over while someone statrs/stops the boiler/circ pump, also try holding that glass full of water with the vent end immersed in it to see if the level falls. What type of filter is installed before the pump?.

I don't get that, you said, above that, "I've got a pump head of 3.0 m but the actual height of the F&E tank water level to the pump is closer to 2.0 m" ?? can you provide a rough sketch also showing where the cold feed is teed in and position of the vent.

It depends on where the cold feed is teed into the system, if its just before the pump (suction) then the pump discharge head is the "height"+the pump head, in your case, 2M+3M=5M. If its after the pump on the discharge side then the pump suction head is the height-the pump head, 2M-3M=-1M, pump running with a negative head of 1M. The rad in my converted attic runs with a very slight negative pressure, if you open the rad vent with the pump running then no water comes out but as soon as you stop the pump, water will start bleeding out, its run that way for ~ 30 years with no problems and heats up fully, as stated above, I require a pump head of 3.6M to fully heat all my rads.

The only reason I can give for noisy operation now vs with the stove is that the stove probably had a much higher resistance to flow because probably a build up of sludge etc over the years compared with the new cylinder resulting in the pump over on start up & (probably) shut down, is there any possibility of raising the vent pipe higher before it turns down?. I am very surprised still at this pump over with a pump developing only 1.0M head, normal pump head would be ~ 3/3.5M, like mine at 3.6M, same set up as yours, pumping into the boiler return but with a "combined" vent & cold feed, they are combined at the F&E cistern. (but I still retained the vent), I have a oil fired boiler with little or no resistance to flow.

If, which it is, the pump is pumping over on start up, then its more than likely that its doing the same on stopping so will eventually draw in air from the vent, your pump (I have the pump curves) will only develop a head of 1M on speed1, a bit surprising that that head is sufficient to heat all your rads, but shouldn't in itself cause that pump over except it starts up at full speed (6M) and then ramps down which I wouldn't expect it to, you said it uses a bit more power than the Grundfos, does it display this power (W), what is the power wherever you are getting it. The pump over often points to a blocked or partially blocked cold feed where it joins the flow pipe, in one of your posts above you show the cold feed & the vent where they are teed into the flow pipe, is the flow from left to right or right to left?. What was the pump power and where did you get that from?.

If you remove the vent then the now combined feed & vent must be 22mm with no isol. valve. What is the height roughly from the F&E cistern water level to the pump and what is the pump set to, speed 1,2or3?. If that height is greater than the pump head, then the pump suction could possibly be running at a negative head and eventually pulling air in, for example if the distance is say 3M and the pump head is 4M, then the pump might be running with a negative suction head of 1M. Anyway try the glass test and give a rough idea of the height and pump speed. Did you have a gas or oil fired boiler previous to the change?

With the pump running, hold a "glass" of water with the end of the vent immersed in it and see does the level start falling.

Looking at the R290 properties, 5.0Bar = 9C & 8.3bar = 24C. And 3.0bar = -6C & 12.54bar = 39.5C. The pressures in the attachment look like absolute, so add 1.0 to your pressures when (if) reading them. Refrigerant R290 Properties.pdf

Its not my boiler I have a oil fired boiler. It was running (CH only for first 2 tests) at a modulation level of 4, I think it goes to 5 max?, 16 rads, all fully open so even with flow/return of 64C/44C, dT 20C will still give a rad(s) output of 60% so no way is this boiler output down to minimum, a dT of 20C with a target temp of 64C gives a return of 44C and a nice bit of condensing. if the boiler can achieve this dT of 20C then far easier than spending hours balancing rads to achieve it?, I would say its a excellent feature if it works.

The boiler flow/return dT can be set in the above by changing a few parameters to set the dT to between 10C and 20C, see attachment. However this does not seem to work for someone I know, it worked to a fashion on CH only but not in HW mode (this isn't a big deal though) The dT was set to its max, 20C in all the examples, below. The best result (briefly) was a dT of 17C with flow/return temps of 64C/47C, pump speed 58%, next best gave 64C/50C, dT 14C, pump speed 64%, and on HW (cylinder), 64C/60C, dT 4C, pump speed 80%. Can someone throw any light on this or if they have a EcoTec Plus try these parametrs to see wht results they get, this boiler is just 1 year old. D.170 is set to 3, which is temperature spread control or dT. Vaillant EcoTec Plus 630 dT.docx