W-plan pump run on

[ShaunCorbs]

S plan it eph

 

[davidwf]

Too much re-work....its only a small 2 bed house and the y plan would be so much simpler to install

 

[John.g]

Look up MOMO mid position valve, these apparently are only powered while changing position or modify a normal MPV, it will then allways return to the unpowerd state, only requires a extra relay.

 

[davidwf]

thanks.... that looks interesting rather than having the motor in a stalkled position 99% of the time.....they seem to be quite rare though
Can anybody recommend / avoid a "normal" spring return one ...

 

[John.g]

thanks.... that looks interesting rather than having the motor in a stalkled position 99% of the time.....they seem to be quite rare though
Can anybody recommend / avoid a "normal" spring return one ...

You can see if you read through the attached Link that the MOMO actuator contains far more circuitry than the conventional MPV, I definitely know that the modified MPV above, (I actually got that nice schematic from the attached Link), certainly seems to extend the MPV lifespan as a very old electrical friend of mine did this very mod years ago, he has since passed on but the MPV is still there and must be ~ 15 years old now. You have a electrical background? so should have no problem in implementing it. Some, mistakenly think that just programming on the HW last thing at night for a few minutes is enough to power down the MPV and it will, but only if the cylinder stat is also, very unlikely, calling, there should be at least a 6/7 hour powerd off state alone each night with the mod since CH is normally the last port of call at night.

Motorised Valves - DIYWiki

wiki.diyfaq.org.uk

 

[davidwf]

thanks but......for simplicity I think I would prefer to go with a conventional 3 port spring return motorised one
Which to avoid though ????

 

[John.g]

thanks but......for simplicity I think I would prefer to go with a conventional 3 port spring return motorised one
Which to avoid though ????

Honeywell, I believe, were the go to product at one time but maybe not so much now, I hear good reports of EPH though.

 

[exedon2]

We use eph stuff all the time very reliable but I still wouldn't fit a 3 port valve.
Your draining down and saving £30 against two 2 ports ain't worth doing .
Y plan = shorter lifespan and more difficult to trouble shoot.

 

[davidwf]

OK, I get the idea (and potential benefit) of S plan and I would be quite capable of plumbing it myself....but....the boiler has an overrun that pumps for around 4 mins.....I already have a manual bypass valve (which is closed as there are NO TRV's in the system) but the bypas loop is literally a 15mm bypass around the pump so surely there will be insufficient "loss" in the simple pipework to dissipate the heat?
As it is, the overrun will pump around the HW circuit
and.... 2 x zone valves are considerably dearer than an EPH mid/3 position one which I can get for £65

 

[davidwf]

any thoughts regarding the bypass loop ?

 

[davidwf]

If I convert to Y plan do I need a mid position or 3 port valve.... I THOUGHT they were one and the same....they both have 3 ports!

 

[John.g]

You can get a (3 port) diverter valve that will give you CH or HW, you can also get a (3 port) mid position valve to give CH only, HW only, and CH&HW, thats why its called a mid position valve.

 

[davidwf]

hmmm...so, If I were to convert to Y plan presumably I need a mid position valve for my installation?

 

[John.g]

Convert from what?, a S plan which has separate 2 port valves for CH & HW or a W plan which has a 3 port Diverter valve as above but only gives CH or HW.

 

[davidwf]

convert from the existing W plan...
If I changed it to S plan, when both are satisfied there would be nowhere for the residual heat to circulate ....as mentioned, the bypass loop appears to be just that - a 15mm pipe around the pump which I am not sure IS a bypass loop as such
"only" CH or HW is fine as it is quite a small house and the HW requirement is low

 

[John.g]

convert from the existing W plan...
If I changed it to S plan, when both are satisfied there would be nowhere for the residual heat to circulate ....as mentioned, the bypass loop appears to be just that - a 15mm pipe around the pump which I am not sure IS a bypass loop as such
"only" CH or HW is fine as it is quite a small house and the HW requirement is low

You could go the conventionel way of installing a ABV between the boiler flow&return if converting to a S plan otherwise convert to a W system with a 3 port diverter valve.

 

[davidwf]

possibly..... just possibly.......
I suggested he turned the CH stat right down and turned the HW stat right up......popped over to the house this morning and found the rads were red hot.
Investigation found that the valve was not returning fully to the home position when the CH satisfied (W-plan remember)……there was no voltage across the motor so nothing could be holding it open
I undid the 2 screws that hold the backplate to the brass valve about 1/2 a turn and the assembly immediately fully opened which should of course close the CH circuit…….did them back up and operated it again and it was quite stiff and didnt return fully…..
I have put two small washers between the backplate and the brass valve to space it out a little bit and it now APPEARS to be working properly !.....hmmm
...and that was a brand new unused Honeywell V4044C1288/U 22mm 3 Port motorised diverter valve, sadly bought off a private seller on ebay so no guarantee, the backplate looks straight and there are no dents or anything anywhere

If it continues to work OK I will take that as a win 😀

 

[davidwf]

You could go the conventionel way of installing a ABV between the boiler flow&return if converting to a S plan otherwise convert to a W system with a 3 port diverter valve.

it already IS (and always has been) a W-plan system with motorised diverter valve..........

 

[davidwf]

pleased to report that it is still functioning correctly as per my findings......so much for buying expensive Honeywell !