Honeywell ABV setting

[John.g]

Its interesting that (if i am looking at the right manual) the boiler HX itself requires a head of 5.2M to flow 1.4m3/hr and they specified a grundfos 15/58 pump which even with a NO loss header will only flow 0.7m3/hr @ 5.2m, the UPS2 15-30 60 will flow ~ 1.0m3/hr @ 5.2M so even if you had two of these pumps installed as you suggested in your post #6 you couldn't achieve 1.4m3/hr on the primary side. The spec seems a bit strange?.
You should certainly be OK though with the UPS 8M as you can still go up two settings more (if required) if you eventually opt for PP operation.

Didn't read the attachment properly, they actually DO specify a UPS 15-78 pump further down which makes sense now.

 

[doitmyself]

Its interesting that (if i am looking at the right manual) the boiler HX itself requires a head of 5.2M to flow 1.4m3/hr

I cannot open the pdf; could you zip it up and post it?

I am also unsure which is the correct manual; all the ones I have found have the pump integrated with the boiler.

 

[John.g]

This one?. Page 11 does seem to specify a Grundfos 15/58

 

[doitmyself]

This one?. Page 11 does seem to specify a Grundfos 15/58

That's because you are looking at the manual for boilers sold in the USA and Canada.

I have attached what appears to be the UK manual for the Open Vented version of the Vitodens 100-W. (See page 8 "Intended Use".) There is nothing in it about the size of pump required.

 

[John.g]

I would like to see the HX resistance, the one I've quoted above requires 5.2M for 1.4 m3/hr (23 lpm) which seems very high??, I'm fairly sure I've seen much lower for other makes of gas boiler maybe ~ 1/1.5M for 23 LPM.

 

[decomplexity]

A wet Sunday, so I thought I would have a look for ball valves with an integral flow meter or with plug-in fixed-flow cartridges. Assuming that the Viessmann 100 WB1B’s minimum flow rate of 200 l/h is acceptable also as a minimum flow for pump overrun, it would be a trivial job to replace the Honeywell DU144 ABV by a simple fixed-flow ball valve such as Cottam’s CP961 (22mm) with a 4 l/min low-pressure cartridge – rated up to 85degC. Are these suitable for CH systems or are they intended for (colder) DHW and I should look elsewhere?

 

[chris watkins]

On this wet Sunday you could have drained your system altered the pipe work so the boiler was able to circulate to a pair of close coupled tees. Put the large Grundfos on the system just after them & set it to auto, refilled your system & been sitting down with a drink admiring your handy work with a boiler running perfectly. (as suggested in post 7)
The 100 WB with a small pump set to a speed to over come the heat exchangers resistance & short pipework loop to the tees will look after itself & any pump overrun. The main system pump wired from the switch lives & set to auto will look after the system as the flow rates change.
Job done or am I missing something?

 

[John.g]

A wet Sunday, so I thought I would have a look for ball valves with an integral flow meter or with plug-in fixed-flow cartridges. Assuming that the Viessmann 100 WB1B’s minimum flow rate of 200 l/h is acceptable also as a minimum flow for pump overrun, it would be a trivial job to replace the Honeywell DU144 ABV by a simple fixed-flow ball valve such as Cottam’s CP961 (22mm) with a 4 l/min low-pressure cartridge – rated up to 85degC. Are these suitable for CH systems or are they intended for (colder) DHW and I should look elsewhere?

It looks OK temperature wise, but since you don't know the valve coefficient (Cv), you may end up having to throttle it to give that 4 LPM@6M head.
What's wrong with your present "Towel Rail" bypass?.

 

[doitmyself]

On this wet Sunday you could have drained your system altered the pipe work so the boiler was able to circulate to a pair of close coupled tees.

Posted in error.

 

[decomplexity]

The serendipitous towel rail bypass is working fine!

But the Honeywell DU144 ABV is also inline and is open even at its highest setting, so in a rare idle moment I was looking at an inexpensive but reliable replacement that would give the constant minimum flow for the boiler on pump overrun. I could of course just replace it by a shut a gate valve, for use only when draining the system.

Your comment about the Cv intrigues me (a person of admittedly little brain): if such a valve is working within its rated pressure range (the low pressure cartridges are 0.2 - 4 bar, and the zero-flow head of the lowest of the UPS pump’s six modes is about 2.2m head), why please would it not give a 4l/m bypass all the time, including on pump overrun?

 

[John.g]

You might please post the pump data sheet again as I don,t seem to be able to easily locate it.
EDIT: OK found them, thanks.

You are running on speed 1 which in effect is a 6M constant head between 0 & 2.3 M3/hr?, the ABV on its highest setting of 0.6 = 6M will not pass any water as it will be closed, have you set it to this index?. If you require to run on a higher pump head then it will start passing, therefore the need for possible removal.

Re the cottam's valve, again I cannot find any technical data on this (the data sheet is blank) but the only way that this will maintain a constant flow rate of 4 LPM between 0.2 and 4 bar is if it is a very clever control valve (akin to a ABV but even better.) If it is a fairly common type ball valve then it will have a certain flow rate (its Cv) in m3/hr @ 1 bar differential pressure, knowing this you can calculate the different flow rates for any given differential head. (Flow is prop. to sqrt head).
Again if you have any data on this please post.

 

[doitmyself]

The UPS2 25-80 is not suitable for your system as it will always be working in the constant pressure part of the pump curve. This is fine for underfloor heating, but not for radiator systems where the rads are turned on and off by TRVs. With a constant pressure an automatic bypass valve will be either permanently closed or permanently open depending on its setting.

 

[decomplexity]

The data spec I was looking at on Cottam's CP961 is attached. Their website has several similar ones, differentiated by the end connection (BSP x 2, compression x 2, ..).

 

[John.g]

Its not ideal but will certainly work (and is), decomplexity requires a minimum flow rate of 4 LPM so the ABV if set to index 0.55/0.56 will (theoretically) achieve this at a 6M head but as you observe there will be a constant bypass flow of 4 LPM at all times. PP (proportional pressure) mode is the most economical way of running but because of its very nature the ABV will "perform even worse" under these conditions, if one assumes that a PP1 setting is required (2.2 to 6.0M) then IF the ABV is set up to pass 4 LPM @2.2M, index setting 0.2, it will pass ~ 21 LPM @ 6m, completely unacceptable. A fixed by pass, if set up to pass 4 [email protected] will "only" pass 6.6 LPM@ 6M, a far better proposition. OR the existing towel rail can (and is) be used which is plumbed in flow/return; downstream/upstream of any zone valves etc so is in the circuit on pump overrun and will not interfere with the condensing efficiency to any significant amount.
I am surprised that the boiler makers havn't introduced some logic in their systems to open a dedicated MV based on minimum flow/pump overrun etc.

 

[John.g]

The data spec I was looking at on Cottam's CP961 is attached. Their website has several similar ones, differentiated by the end connection (BSP x 2, compression x 2, ..).

Thanks, I've seen those, I will be very impressed if that will control the flow rate automatically, might be worth giving their technical dept. a buzz?.

 

[ShaunCorbs]

There for limiting water flow eg cold and hot

Won’t be any good on heating and will short circuit as always open

 

[John.g]

They claim +-15% accuracy at the lower pressures but maybe this is only if one side (end) is open like a tap etc?.
https://renergise.ie/wp-content/uploads/2014/07/In-Line-Flow-Regulating-Valve-Brochure.pdf

 

[decomplexity]

I have just emailed Cottam and Preedy to ask if there are technical (or duty cycle) reasons why usage should be confined to DHW - such as (as John.G says) the downstream end being 'open'

 

[doitmyself]

Grundfos recommend the Taconova "Setter" valve if a fixed flow rate is required.

 

[John.g]

Yes but the "wondervalve" above claims that it will (or might) maintain a fixed flow with a varying pump head as will occur with PP operation. The setter valve is recommended for a pump on a CP (constant pressure) setting but the flow would vary in pump PP mode?.