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Discuss Change to S plan or stick with Y plan in the Central Heating Forum area at PlumbersForums.net

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I currently have a 28mm Honeywell 3 port valve that works, most of the time, occasional blip by ball sticking or staying mid position or whatever. I have a pair of 28mm Honeywell
2 port valves and have contemplated for a while ditching the 3 port and fitting these. This obviously entails some work. The pipework leaves the pump obviously in 28mm as do the supplies to DHW and CH so would it be worth me swapping over or should I just stick with the 3 port, changing it for a new one. Obviously going to S plan I would need a 28mm T piece, or would I? Could I leave the 3 port valve bodywork in place and just remove the gubbins so it just acts as a T piece. If I fitted 2 port valves they would be on the return legs which I assume is not a problem.
 

SJB060685

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I don't like the 3 port mid position valves, their very nature means they can burn out over time, more frequently than a 2 port. If you decide to swap to two 2 ports I would want them on the flow, which would mean removing the entire 3 port and doing a little repiping. I wouldn't want the 2 ports on the return as this can cause thermal drift, whereas a little bit of energy will always be seeping to the circuit without demand.
 
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494
Nothing in life is easy I will swap to the 2 ports, I can just about squeeze them in the flow pipes, only considered putting on returns as much longer lengths accessible. What about the idea of keeping the body of the 3 port instead of fitting a T piece?
 
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494
No that is on the list as well. Think it had something once but just two stop ends now. Talking of auto bypass valves there seems to be a massive variation in prices.
A Honeywell one at over £60 and an no name job at £10. And finally the flow from the boiler arrives at the pump in 28mm can I use a 22mm by pass valve?
 
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494
Just as a slight addendum to this thread I contacted Honeywell about fitting a 2 port valve in a return leg. I was given the answer no for the following reason. Was told there was a chance of the rubber ball being pulled off the sealing face and letting by. Would
agree with that as a possibility, a small one at that, but why does it not then apply to it being on the flow side. Between the flow and return we only have a few feet of pipework inside the DHW cylinder so I would have thought any suction force caused by the return would be present on the flow at the entry to the DHW cylinder.
 
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2,199
No that is on the list as well. Think it had something once but just two stop ends now. Talking of auto bypass valves there seems to be a massive variation in prices.
A Honeywell one at over £60 and an no name job at £10. And finally the flow from the boiler arrives at the pump in 28mm can I use a 22mm by pass valve?
Don't know what make/model of circ pump you've got, but, increasingly now, ABVs are almost impossible to set up properly as even the traditional 3 constant curves (Fixed Speed) are not like the old and real CC curves in that at the lower flow rates, they perform, in effect, in CP (constant pressure) mode so you may up having to fit a manual by pass, no problems like that with your existing set up.
 
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494
Grundfos Alpha 2L, for what is worth. I see all these flow charts they list, gobble de gook to me and rapidly move on. Might be easier just to have one rad with no trv, ie utility room ticking over at all times. Would keep the back entrance, excuse the term, warm as this is the outside door we use the most.
 

ShaunCorbs

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Aslong as it was in the correct orientation eg same direction of flow

Then it doesn’t matter can be on the flow or the return tbh better as it’s lower temp
 
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494
See that was my sentiment until I started getting conflicting info from other sources, I will probably end up putting it on the return
as suitable pipework is in situ already. Can I ask one other question? It is regarding the question I have already posed that is regarding a parallel thread radiator tail. I am only a DIYer but use loctite 577 for radiator tails which I always thought were tapered threads. That is until I got a couple of extended ones which are parallel thread, seems all extended tails are parallel, not sure why.
I contacted Henkel asking could I use 577 with 55 cord was told no, they suggested 577 with LOCTITE SF 7649, yet another spanner in the works.
Anyway less of this waffling what would you use to seal a parallel thread radiator tail? I still have Boss White and hemp!
 

ShaunCorbs

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Tbh if it goes in the thread (the rad tail) and it doesn’t stop / all the way by hand loctite 55 if it stops with 2-3 threads showing 577
 

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