Replaced heat only boiler now overheating

[Ponja]

I had an ideal classic he 15 heat only boiler running a boilermate ov class a thermal store. The thermal store has a grundfos 15/60 pump on the boiler return.

Replaced with a baxi 415 (because no overrun and no live required which simplifies things).

Thermal store refilled all things working expect new boiler immediately overheating. Wondering if this could be because the ideal had an overrun pump so now I've lost head/flow rate? Gas engineer coming to check it out tomorrow (we had to wait for refill), but ideas would be welcome.

 

[cross thread]

Flow / return wrong way round ?

 

[Ponja]

I guess it's possible why are you guessing that?

The gas engineer took the pipes from the previous boiler left return and right flow so unlikely to be wrong.

 

[Ponja]

Now that I'm thinking about pretty sure the left side (return) was getting hotter than the flow side. Oh dear I really don't want to have to drain this down again...

 

[Johntheo5]

The Baxi has its return R on the top left, outer, with the Flow F immediately to its right. The logic is somewhat similar but the Return is on the Top, extreme Left and the Flow on the Top, extreme Right?.

 

[Ponja]

Yes all correct John (except the old one is a classic HE), I'm not sure if the engineer didn't check if there was a crossover when he removed it, once it was off we agreed return left and flow right on old and new boiler but somehow it's ended up reversed. No bother he will come back and switch and hopefully that sorts it. At least there's a clear potentially fixable problem and hopefully I don't need another pump. Also gives me a chance to pour some x400 down my thermal store which I think it badly needs.

 

[cross thread]

So how has he managed to commission it correctly?

 

[Johntheo5]

They don't build them like they used to, I changed a circ pump on a 20 kW SE Firebird for a neighbour about 6 years ago and found that the circulation was the wrong way round and had been for about 9 years, he had found that he had to keep the boiler stat dial setting well down to keep a reasonably low flow temperature!!!

 

[Ponja]

Good question, it's not commissioned, he left as my system takes many hours to fill. He tested it briefly when partially full and it was overheating we thought maybe it would stop when full. He was supposed to come back today to comission it but I checked if it was working once full yesterday and noticed the heat coming from wrong pipe. So will have to fix and comission later.

 

[Ponja]

That was my first potential solution but temp knob has a sticker as I'm not supposed to mess with it yet! Swapping directions sounds slightly better