Tim S Posted April 29 Share Posted April 29 Hi everyone. the lengthy saga of my ashp installation continues! Thanks to everyone who messaged me or otherwise had suggestions for getting the electrical side done. I am possibly sorted now, but the sparky has been a bit wary of the whole process. I’ve settled on a 5kw Ecodan with the FTC2BR controller and am using Wunda H box wiring centre / manifold etc I remember on here somewhere there being a discussion about incorporating relays into the system but I can’t remember where. Could anyone direct me to the thread or possibly give me a steer as to whether I need to check the sparky has thought about this? Many thanks Tim Link to comment Share on other sites More sharing options...
JohnMo Posted April 29 Share Posted April 29 Things I have seen, the wiring centre you mentioned gives a 230v or volt free output to the boiler/heat pump, so no idea why you need additional relays? Assume you have a buffer to keep heat pump happy with zoning? Link to comment Share on other sites More sharing options...
Tim S Posted April 29 Author Share Posted April 29 Hi Johnmo yes the wiring centre appears to have one volt free or 230v output. However there will be two pumps and zone valves, one each for dhw and UFH, so I was wondering how the second one is switched? No liquid buffer, but it’s a pipes in slab UFH arrangement, so the 35 odd tons of concrete should buffer pretty well I would have thought… cheers Link to comment Share on other sites More sharing options...
JohnMo Posted April 29 Share Posted April 29 14 minutes ago, Tim S said: However there will be two pumps and zone valves, one each for dhw and UFH Have made life really difficult for yourself? A simple 3 port diverter would be fine. Cylinder heating is normally done with the heat pump circulation pump, this pump is controlled by the heat pump it's self. Also your zone valve would be powered from the heat pump control or directly by the thermostat on the cylinder. That valve needs to fail closed for G3 requirements. Your UFH pump would be controlled by either wiring centre or directly from the zone valve micro switch, valve open pump starts. A normally close and normally open two port would have made life easier. But you can use the micro switch on one DHW two port as the opening switch for the other valve. With a heat pump both shouldn't be open at the same time, but should open and close in unison so flow path is never closed for the heat pump, otherwise you will trip the hp on low flow. Next question do you need the wiring centre at all? You may get an issue on pump start delay caused by wiring centre. The 5 minute delay in pump start is slower than the heat pump start up and will cause flow issues. Do you need UFH pump at all? If you do, could you not wire zone valve directly to thermostat? Then pump to zone valve micro switch? Link to comment Share on other sites More sharing options...
Tim S Posted April 29 Author Share Posted April 29 Interesting. Mitsubishi technical pre sales told me that their Ecodan monoblock does not have a built in circulation pump. Then again, they also told me that the FTC2BR controller had to be used with a BEMS system. Doesn’t particularly inspire confidence! I had originally planned to use it as you say for cylinder heating, and Wunda specced and supplied another pump on the manifold for the ufh side. It is possible I would need an extra pump on the dhw as I’m using two towel rails teed off it to run at the higher temp than the ufh temp for early morning and evening bathroom temp boost and the pipe runs are quite long…. Link to comment Share on other sites More sharing options...
JohnMo Posted April 29 Share Posted April 29 28 minutes ago, Tim S said: han the ufh temp for early morning and evening bathroom temp boost Running at a higher flow temp just for that is bonkers. Just make them electric, TEMA do various output immersion to screw in to rowel rads and external thermostat for programming. 32 minutes ago, Tim S said: Ecodan monoblock does not have a built in circulation pump Ok the control of an external pump then would still be controlled by the heat pump. If you dump the water heated rads, no need for mixer or additional UFH pump. You just need to control zone valves. Link to comment Share on other sites More sharing options...
Gary68 Posted April 29 Share Posted April 29 Agree with Johnmo I have an ecodan I had an extra ufh pump fitted and a wiring centre with actuators and zoned thermostats. 5 years later it’s all redundant never needed in the first place all the actuators are disconnected all zones open all the time ufh pump is turned off water flows round quite happily when the heatpump is on. Probably £500 of waste if it was designed correctly in tne first place Link to comment Share on other sites More sharing options...
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