Headscratcher Posted September 19, 2019 Share Posted September 19, 2019 I have had a wet system installed in my house. 5 port manifold with IBO pump and blending valve. 2 port valve installed to allow the UFH to run on it's own circulate with one radiator linked to it to deal with excess boiler heat. I have a combi boiler. Problem is: when the thermostat calls for heat everything is initially fine.. 2 port valve opens, UFH pump kicks in and heat flows from boiler through blender valve... all going well after about 2 mins, the flow metres start to show no flow and the temperature in the manifold drops, with no hot water being mixed. If I then reduce the temperature to 30 degrees on blender valve, the water temperature ramps up in the manifold and I can then gradually reset it to 45 degrees and all is okay. Without this self adjustment the water in the UFH stays at around 20. Thoughts? Link to comment Share on other sites More sharing options...
ProDave Posted September 19, 2019 Share Posted September 19, 2019 Has it EVER worked properly? If not it sounds to me like flow and return to the manifold may be connected backwards. Link to comment Share on other sites More sharing options...
dpmiller Posted September 19, 2019 Share Posted September 19, 2019 are the flow and return from the boiler reversed maybe? 1 Link to comment Share on other sites More sharing options...
Headscratcher Posted September 19, 2019 Author Share Posted September 19, 2019 Flow and return are plumbed in correctly and UFH works as it should once i have done my routine with the blender valve of lowering the temperature and then gradually increasing it... I have checked the pump direction and flow and return from boiler and all is installed correctly. Link to comment Share on other sites More sharing options...
ProDave Posted September 19, 2019 Share Posted September 19, 2019 Can you post a picture of the manifold and it's blending valve arrangement? Link to comment Share on other sites More sharing options...
Temp Posted September 19, 2019 Share Posted September 19, 2019 Moderator may need to allow you to post some photos as you are anew member? Link to comment Share on other sites More sharing options...
Temp Posted September 19, 2019 Share Posted September 19, 2019 Some manifolds have an "over temperature stat" that limits the floor temperature to prevent damage to some types of flooring and burnt feet. Perhaps this is set too low? Link to comment Share on other sites More sharing options...
Temp Posted September 19, 2019 Share Posted September 19, 2019 (edited) Just now, Headscratcher said: Problem is: when the thermostat calls for heat everything is initially fine.. 2 port valve opens, UFH pump kicks in and heat flows from boiler through blender valve... all going well after about 2 mins, the flow metres start to show no flow and the temperature in the manifold drops, with no hot water being mixed. Does the ufh loop pump stop or does it keep running when the fault occurs? Edited September 19, 2019 by Temp Link to comment Share on other sites More sharing options...
Headscratcher Posted September 19, 2019 Author Share Posted September 19, 2019 56 minutes ago, Temp said: Does the ufh loop pump stop or does it keep running when the fault occurs? The pump keeps running. I am completely bamboozled. I think it might be an issue with the blending valve. Link to comment Share on other sites More sharing options...
Headscratcher Posted September 19, 2019 Author Share Posted September 19, 2019 1 hour ago, ProDave said: Can you post a picture of the manifold and it's blending valve Not a great photo unfortunately. Link to comment Share on other sites More sharing options...
Headscratcher Posted September 19, 2019 Author Share Posted September 19, 2019 Link to comment Share on other sites More sharing options...
Headscratcher Posted September 19, 2019 Author Share Posted September 19, 2019 1 hour ago, Temp said: Some manifolds have an "over temperature stat" that limits the floor temperature to prevent damage to some types of flooring and burnt feet. Perhaps this is set too low? I don’t think there is an over temp stat installed Link to comment Share on other sites More sharing options...
ProDave Posted September 19, 2019 Share Posted September 19, 2019 That is exactly the same manifold as I have (mine came from someone on ebay) So on the blending valve, the pipe coming in from the bottom is the flow and the pipe exiting to the left is the return. I changed my IBO pumps for WILO (because the IBO ones were far too noisy) so I don't have one to hand for a direct comparison, but the flow of the pump (it has an arrow on the body) should be upwards. I don't think it is a blending valve issue as even if the valve is not asking for any heat, it should just recirculate, so I wonder if you have the pump the wrong way up? Link to comment Share on other sites More sharing options...
Temp Posted September 19, 2019 Share Posted September 19, 2019 +1 to check the pump direction. I looked at the manual but it's not clear. The drawing that shows the permitted installation orientation suggests it might be installed pumping downwards by mistake. However if that was the case I don't think the flow meters would work? 1 Link to comment Share on other sites More sharing options...
Headscratcher Posted September 19, 2019 Author Share Posted September 19, 2019 44 minutes ago, ProDave said: That is exactly the same manifold as I have (mine came from someone on ebay) So on the blending valve, the pipe coming in from the bottom is the flow and the pipe exiting to the left is the return. I changed my IBO pumps for WILO (because the IBO ones were far too noisy) so I don't have one to hand for a direct comparison, but the flow of the pump (it has an arrow on the body) should be upwards. I don't think it is a blending valve issue as even if the valve is not asking for any heat, it should just recirculate, so I wonder if you have the pump the wrong way up? Spot on. I have just removed the mixing valve and the pump to learn that the plumber installed the boiler flow into the boiler return... so annoyed. I have been battling with this issue for ages and was assured on numerous times it had been done correctly. The indicators are on the bottom of the valve so without removing it, t’was hard to see. thanks for your help. I now somehow have to reconfigure the pipes which is going to look super untidy. 1 Link to comment Share on other sites More sharing options...
Headscratcher Posted September 19, 2019 Author Share Posted September 19, 2019 5 minutes ago, Temp said: +1 to check the pump direction. I looked at the manual but it's not clear. The drawing that shows the permitted installation orientation suggests it might be installed pumping downwards by mistake. However if that was the case I don't think the flow meters would work? Thanks. Found the issue. Flow and return piped incorrectly on mixer... see my response to ProDave. thanks for your help Team DIY. 1 Link to comment Share on other sites More sharing options...
ProDave Posted September 19, 2019 Share Posted September 19, 2019 Glad to have been of help, it was just lucky I have the identical manifold. 1 Link to comment Share on other sites More sharing options...
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