7 head pump upgrade on an Intergas boiler

[happyflyer]

This is interesting, the statement below in red is from the Intergas IM, can any of you experts tell me why Valliant put the ABV inside the boiler
and not suggest it be 20 ft away, if you guys ever put an Intergas in a terraced house and you can't fit the bypass 20ft away, you will fall
foul of Intergas IM, whatever will you do. What they appear to be suggesting is that some heat loss is set into the equation not just minimum water flow
through the boiler, if all the 20 ft of pipe was lagged, what then, I would be interested on your take on this.8.1.2 Thermostatic radiator valves


If all radiators are equipped with thermostatic or radiator valves, an auto bypass must
be fitted in order to guarantee minimum water circulation. The auto bypass must be at
a distance of at least 20 ft from the appliance in order to prevent overheating of the
appliance. A radiator without thermostatic valves is not a suitable by-pass.

 

[Mike Jackson]

It's there to comply with the building regs. The bypass inside a boiler is there to protect the pump and not to comply with the building regs.

 

[happyflyer]

Mike are you saying that if you fit a Valliant you need to also fit another ABV 20 ft away from the boiler ???


Mike PS you are right, IM for Valliant, wonder if plumbos are fitting one, two of my friends have Valliant with no external BP, if one bypass can give a plumber a headache setting up two what will that do, if someone has a flow problem we should be saying, " have you set both ABV "

3.13 Bypass


A system bypass will be required fitted at least 1.5
metres away from the boiler, refer to the current issue
of central heating system specifications (CHeSS).

 

[evets51]

Just an update to say thanks very much for all the advice. I had a very educational chat with happyflyer yesterday who was very generous with his time. It turns out one of my major problems is the towel radiator fitted as a bypass. The valves were wide open and its plumbed in larger bore plastic pipe - so all the hot water was screaming around there and back to the return pipe rather than going around the radiators. Last night I closed both valves and then opened them one turn only - this morning the system was much much faster to heat up, far less boiler cycling. I still have problems as more than half my radiators have a TRV on each end and no lockshield valves so impossible to balance - going to get those replaced and attempt balancing, and fiddle some more with the valves on the towel rail bypass to try to get it perfect. But certainly seem to be on the right path.

 

[happyflyer]

Steve,

When you have the items done I have suggested, I will help you balance the system, it will be a little more demanding than a newly installed system since the different bore diameters, I will be sending you another email today about the towel rail bypass and the proper alternative.

BTW you forgot to mention there is no balancing valve on the primary return on the cylinder coil too and the water is screaming around there when the HWS valve is open.

Tony

 

[Leo21]

Here goes! Why do you need a bypass on a "y" plan? There's always a port open to either the cylinder or a bypass radiator! Both long enough runs and usually longer than where the bypass would be fitted.

 

[evets51]

Here goes! Why do you need a bypass on a "y" plan? There's always a port open to either the cylinder or a bypass radiator! Both long enough runs and usually longer than where the bypass would be fitted.

Its an S plan I believe - 2 separate motorised valves, one for hot water and one for heating.

 

[evets51]

not when its a system boiler.
so the boiler is short cycling, turning itself off because it is up to temperature, so what temperature is the return pipe??
is there one or two radiators that get piping hot quickly? = balancing issue.
have the parameters been properly set?
ch power to max 85 percent??
is installation type set to position 3- heat only!??

Yup it appears to be balancing as said above. The ch is on max 85% though yes, pump speed is turned up to max and installation type is 3.

 

[doitmyself]

the pressure drop on the Intergas alone is rather high to start with.

Why do you say that? The 18SB (OP's boiler) drop is only 0.75m at full output, which leaves 3.5m for the heating circuit.

Don't forget that the boiler is designed to work with a 20C differential, so a lower flow rate and consequently much lower pressure loss.