Diablo

Hi, Not sure about the shower mixers. They are concealed Hansgrohe mixers - thermostatic? I just checked and the cylinder stat is set to about 60oC. The boiler flow is less than 60o, as it is below half way (which is 60o) in effort to ensure my return is below 56o. I guess the issue is that the boiler will cycle unnecessarily for the 2 hrs a day we have it heating DHW? Is it more critical to get the boiler return temperature below 56o, even if this means the boiler flow is below the cylinder stat? Many thanks.

I think I'll go with a nice Gunmetal Grey! Thanks for the info.

All, I have some questions about settings for UFH heating system, which was installed a year ago but was not correctly balanced by the installers as there no boiler in the property at the time. I have 2 Reliance manifolds (7 port and 9 port), currently set at 45deg and pump speed 3. The pipes are 15mm and set in a 75mm sand and cement screed. Any advice on optimal settings and how to balance the system? There was a similar thread recently, but did not wish to highjack it Many thanks, Rog

A quick update: Whilst I have not got around to taking a reliable temperature reading from my copper flow pipes (for reasons explained by Jeremy), I have turned the boiler stat down from just below max. I initially set it half way (60 deg flow temp) and guesstimated that the return temp must be 56 deg or lower. I still had plenty of DHW and the heating seemed to run fine. I noticed that my shower mixer was delivering hot water when I had it at about 60% of max temperature. This got me thinking whether about further efficiency gains and the fact that DHW was still being heated to a temperature far higher than I needed in the shower so, I turned the boiler stat down a little more...I now have to turn my shower mixer to max to have a nice hot shower. I am wondering whether in my simplistic thinking I have hit the efficiency 'sweet spot' for my system? Certainly, my Oil Watchman gauge shows no movement in the last three weeks!

Hi, Yes, it is a condensing boiler, but I should add that it is oil fired. What is the best way of measuring return temperate? I have an infra-red thermometer gun? Also, should the measurement be taken when the heating system is pretty much up to temperature?

Now that my hot water issue has been solved, it has got me thinking whether my boiler thermostat is set correctly. The plumber that installed it reckoned it should be set to near enough max (75 deg) on the basis that the boiler will run for less time to get the UFH up to temperature and will get a faster response. The UFH is set to 45 deg and the manifold pump is set to max flow (setting 3 on the pump). Also, any thoughts on what a typical temp setting is on the UVC stat? The showers are now so hot that we have the mixer set at just over 50%, so leads me to believe we might be heating water unnecessarily. Thanks in advance.

A quick update: The plumber fitted a double check valve below the pump and everyone's happy! Thanks for the help.

Gents, This is fantastic and your help is hugely appreciated! I have checked the UVC and I cannot see any option to feed the HR higher up. As it happens, I had a plumber booked in for tomorrow morning to do something else, so I will get him to address this issue at the same time. I will report back asap. All the best, R

Hi PeterW, Wow...I closed the isolator above the pump and the water in the shower seems much hotter and stayed consistently hot. The HW at the kitchen and laundry taps (much closer to the tank) are also much hotter.... If you get a moment, I would love to hear your thoughts on what is going on??? Can I leave the isolator closed? Meanwhile, thanks so much for your help!

Hi, It is a UVC. The three zone valves (2 for UFH and the other for DHW) are on the flow pipe coming off the boiler. Let me know if you need any more pics (hopefully you don't need any of me in the shower ) Let me know if you want me to post any other pics.

Hello, the DHW does indeed feed from the top of the tank and returns closer to the bottom (Main 300 UVC). In our case, the circulator pump definitely seems to help draw the water out of the cylinder. If I switch on the shower at a given temperature setting but at e.g. 50%, I might not get hot very hot water. If I open the shower tap fully (leaving the temperature unchanged) it does appear to get warmer. Other times, the water will cool down in the middle of a shower, but I have found that switching on the circulator pump seems to help. Again, it sounds as the system is struggling to get the hot water out of the (bottom?) of the tank. Thanks again.

Guys, I live in a new build bungalow with an oil boiler which fires the UFH system and 300L unvented HW cylinder. This is our first winter here and I have noticed a few issues with the heating/hot water system: Q. When the UHF comes on at the same time as the HW, it seems to starve the supply to the HW circuit as I frequently end up having luke warm showers. Is there any way of ensuring the cylinder gets sufficient supply? Q. The other thing I have noticed is that there can be warm water in the tank, but unless I switch on the secondary hot water circulation pump, we do not get hot water to the bathrooms. The furthest bathroom is about a 20m horizontal run from the tank. I am loathed to keep the pump for any long periods of time, as it would mean that hot water is being pumped around a cold loft space. Does anybody know what is causing this and how to get around it? Any thoughts or advice would be gladly received. All the best, Rog

Our floor build up is: Concrete slab, 175mm of EPS70 and a 70mm screed. UFH is based in 16m pipes at 100mm centres. Floor finishes are either porcelain tiles or carpet (low tog) I have noticed that the boiler runs for long bursts, rather than cycling frequently. It only runs tepid when there is demand coming from both manifolds and DHW. UFH or DHW, in isolation, seem to run fine. A plumber who was doing some other work on the property mentioned that we might need a low los header?

I feel your pain. I had similar issues with my builders, who thought I was being overly pedantic. If Rockwool Technical (who are very good, BTW) suggest replacement, perhaps the builders should contribute to replacement costs??

IIRC, the plumber made a modification as follows: He Tee'd off from the boiler output pipe (prior to the boiler's pump) and supplied the two UFH manifolds. The boiler's 'pumped' supply goes to the cylinder only. The thinking behind it was that there would be sufficient pressure to get the hot water to the manifolds and their respective pumps would take over thereafter.

Hi, It is a System boiler with integral pump. I cannot see any gate valves in line with the cylinder, just a bleed valve and two pressure relief valves.

The boiler, Manifold 1 and the DHW tank are all in the laundry room, so in close proximity. In the middle of the house, we have Manifold 2, which feeds the right side of the house. Both manifold are set at 45deg. We have attempted to 'balance' the demand a little by setting the pump on Manifold 1 at setting two and Manifold 2 on setting 3 seeing as it is further away. I will get some temperature readings. Do you see any issue with what I have described so far? (PS: I should add that the UFH manifolds have not been balanced yet, as the UFH pipes were put in well before the boiler was installed - not sure if this would have any impact?)

Hi, We have two UFH circuits and DHW circuit, each with their own zone valves. The issue occurs when the DHW and UFH valves are open. DHW takes much longer to heat up. It's as though the UFH system takes the majority of the HW coming from the boiler.

Gents, I live in a 240sqm bungalow that we built last year. This is our first period of cold weather, so we are using the heating system properly for the first time. We have a 21KW oil boiler feeding a UFH systems that runs throughout the house, and a 300L unvented cylinder. We try to maintain about 20deg in the house which means that one stat, or other, will be firing the boiler at some point in the day. The issue I have found is that the when the heating is on, the pipes going to the DHW tank become tepid. If I go around and switch off the stats, the same pipes warm up considerably. Is this just bad design? Any thoughts welcomed. Best regards,Rog