C/F and O/V config issue

[bigads28]

I have a problem with a large restriction that's caused by the pipework config I think, but I'd like to know what everyone else thinks.

There is very poor circulation from a 38kw Ecotec installed 3 years ago, which is down to restrictions in the cold feed and flow upto the pump. I'm going to repipe that blocked part but don't want to have to do it again in 3 years. There must be 10m of head on the boiler and the pump is set at 3. It's a big house with 15 rads and cylinder.

I'm wondering if I should combine the c/f and o/v or if I should move the o/v off the T and further along the flow pipe. I've had problems with o/v coming off the T before but those system didn't have the head this one does.

The blue line shows where the restriction is and I'm going to cut it all out and replace.

Thanks for your thoughts folks!

 

[wattsie1987]

Are the primarys 28mm?

 

[Ermintrude]

Was going to ask the same. Bigger pump bigger primaries filter and don't combine but fit 28mm o/v and c/f for first meter then step down to 22. Also if in hard water area u could fit a strainer and use that as a scale collector. Just take it out and bang it clean every year?

 

[stevetheplumber]

38kw definitely needs 28 mm primarys

 

[doitmyself]

here is ... a 38kw Ecotec. ... It's a big house with 15 rads and cylinder.

I bet the rads don't add up to 38kW; probably about 22kW.

There must be 10m of head on the boiler and the pump is set at 3.

Do you mean it's about 10m from the FE tank to the boiler? If so, that's irrelevant when setting the pump. It's the pressure loss and flow rate round the heating circuit which determines the pump setting.

 

[bigads28]

I would only be able to get about 1m of 28mm in for the F/R, it's reduced pretty quickly coming out of the boiler. The c/f is 15mm and would be impossible to upgrade. Same for the o/v its 22mm. Soft water up in baltic Scotland!

 

[Ermintrude]

Humm it's pipework you have issue with me thinks [emoji90][emoji378][emoji379]

 

[bigads28]

I bet the rads don't add up to 38kW; probably about 22kW.


Do you mean it's about 10m from the FE tank to the boiler? If so, that's irrelevant when setting the pump. It's the pressure loss and flow rate round the heating circuit which determines the pump setting.

It's struggling to get 22kw probably tbh, it won't circulate properly because this restriction. I can remove this but don't want it to return. I'm trying to see if there is a way to improve the configuration with what I can access.

 

[bigads28]

Humm it's pipework you have issue with me thinks [emoji90][emoji378][emoji379]

I will replace the f&R with 28mm and just reconnect the c/f and o/v but move the vent along the pipe and off the T.

The house was referbed about 3 years ago and everything is behind false walls and ceilings. Pain in the arris!

 

[doitmyself]

It's struggling to get 22kw probably tbh, it won't circulate properly because this restriction. I can remove this but don't want it to return. I'm trying to see if there is a way to improve the configuration with what I can access.

But if you only have 22kW of rads, you don't need a 38kW boiler (unless it's a combi with a very good incoming flow rate). So you can range rate the CH output to say 24kW.

What is the temperature differential across the boiler? It should be nearer to 20C than 10C.

 

[AlexGas]

I have a problem with a large restriction that's caused by the pipework config I think...

Did you check if there is much air coming out of the pump priming plug? The pump shouldn’t be in this position, it could give you a circulation issue.

 

[bigads28]

Did you check if there is much air coming out of the pump priming plug? The pump shouldn’t be in this position, it could give you a circulation issue.

Yeah there is Alex, I couldn't understand where it was coming from with such a large head. I think its more the tiny cold feed that snakes its way through the house. I'm wondering if it's pulling air off the open vent which also snakes its way through this house. Its an old stone house and the boiler is in an add on at the back.

I reduced the heat output to 25kw ( thanks doitmyself) and that stops the boiler going into this limp mode where it runs at minimum (S53). The quote is in for upgrading the pipework, but I'm gonna phone Vaillant to see if I can have just a single cold feed and no vent because of the O/H stat. I'm not sure if they allow this but it would save major hassel!

 

[tamz]

Jst alter the pipes in the attic to make it a combined feed and vent, turn the pump correctly on its side and turn the speed down. Not many systems need speed 3.

Inverted feeds can be more troublesome with blockages but very unusual after 3 years unless the system is seriously mingin.
Cut it out anyway but i doubt if that is the problem. Stick a magnet on it and you'll know.

 

[wattsie1987]

I would be looking at 28mm primarys. Magnaclean and 28mm feed and vent tees.