Thank you so much ! I keep getting told especially from this forum that an Intergas boiler HRE OV is the only suitable boiler to choose given I havea one pipe system and big bore pipework - I think I ll take the 30KW choice - I have a gas enginner who replaces combis all the time - He has asked me to get a boiler and flue on site and he will install ! I cannot afford the 5K plus vat quote sadly!
Two pumps on a heat only boiler quotation
- Thread starter JackK
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Enough of the offhandish comments...
I do this for a living!
I have not been to your property!
Each situation is different.
You cannot solve this from a distance or from a book!
As I said above...
Get 3 quotes and question each ATTENDING engineer based upon what you have learned thus far!
From... The pottters guy who said one pipes can be a PITA!
I now recall why I've been absent from this part of the forum!
No good deed goes unpunished FFS!
NO 2 SYSTEMS ARE THE SAME!!!
MASS FLOW RATE
Even if the alternative "cheaper" option doesn't work?
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That is the only sensible thing to do and I had assumed that was what the OP was going to do.
I thought you gave fantastic advice. That would be a shame.
Unfortunately just saying 4 beds is a bit meaningless.
We have just completed what is currently a 4 bed property with a 35kw heat load but 2 of beds are 16mts x 8mts not including en suites!
We regularly deal with large one pipe systems admittedly oil systems but the principle is same.
We always use a suitably sized plate to plate to separate new boiler from old system.
I hope your 'gas engineer ' is not a combi box slinger or you may be in trouble.
We have just completed what is currently a 4 bed property with a 35kw heat load but 2 of beds are 16mts x 8mts not including en suites!
We regularly deal with large one pipe systems admittedly oil systems but the principle is same.
We always use a suitably sized plate to plate to separate new boiler from old system.
I hope your 'gas engineer ' is not a combi box slinger or you may be in trouble.
Wonder what his condy arrangement would look like?
Vaillant 438 will fail for circulation. It is a known issue when a big boiler like this and ss hex is concerned.
Have attended several installations where boiler shuts down when flow and return differential is too large.
First pump is creating a ‘hot ‘ loop. Second pump is taking water from this loop and sending it to the radiators.
If a 38 kw boiler has been speced, then you must have a big house with lots of pipework hence the more powerful pump
Finally, mexico waterways are like big canals which offer little resistance to flow of water.
If you are not happy with the quote, reject it. Me? I would go for it.
I did not mean to cause offence - I had three gas engineers and the advice ranged from use a combi, rip out and start again and the final engineer was 5K for a valiant ecotec 438 keeping it open vent
So I turned to this forum to get the real inside information - I realise that a site visit helps but euqally there are guiding principles - There has to be - Floor space, number of rads, size of pipes are the information I provided - That should hopefully give an idea of the type and size of boiler needed.
If there is any further info that can be used to help others I would happily provide it - So far I reaise i need a 8M pump and a 30KW boiler - I still dont know how important a plate to plate exchanger really is!
So I turned to this forum to get the real inside information - I realise that a site visit helps but euqally there are guiding principles - There has to be - Floor space, number of rads, size of pipes are the information I provided - That should hopefully give an idea of the type and size of boiler needed.
If there is any further info that can be used to help others I would happily provide it - So far I reaise i need a 8M pump and a 30KW boiler - I still dont know how important a plate to plate exchanger really is!
Thanks - I also heard valiant will clog up very easily because of sludge even if if cleaned so I was pointed to Intergas as the best for dirtish water - My pipework is steel so there wil be corrosion even if inhibitor added.
I Was aware of the differential between flow and return but advised that can be guarded by increasing the pump speed
The ideal mexico 2 does work but I wouldl ike a change - So I thought a OV Intergas would be a swap - Now it became a new pump needed - fine - Then its a plate to plate heat exchanger
If someone needs a big open vent boiler e.g. 35 KW, which is the most free flowing and least likely to clog. It look like Intergas OV only goes to 27KW actual output. Is it Worcester Bosch 8000? Someone told me you can actually get the really big Intergas system boiler and remove the pressure sensor and run it OV.
Also, I can't see Vaillant 438 on the website. Maximum is 435 and it says it has an aluminium HX. Would this be a better fit?
Also, I can't see Vaillant 438 on the website. Maximum is 435 and it says it has an aluminium HX. Would this be a better fit?
Vaillant series 4 used to be stainless steel Hex. Now might be alloy hex.
Be aware of Intergas boilers as these require burner seal replaced every two years. I invest3d in a torque wrench to tighten the bolts on it. Also need special grease for the bolts. Cannot see average poke and hope chap going to this length to service the boiler. I like the boiler but it comes with its extra burden. Have fitted a few, especially old boiler replacements that were open vented, now working as open vented combis.
Just looking at it from another angle re need for LLH/PHEX etc from a thermodynamic point of view. I did these calcs below for someone or other who had a problem 7 rad, one pipe system and wanted to know the theoretical flows required to enable every 1.5kw rad to give its rated output, I can't really remember but I think he said that the boiler dT was too low and the boiler was sensing this and tripping. You can see from the (virtually impossible to achieve in practice) calcs that the dT is ~ 7C so in practice would assume that this is a lot closer??.with the rads output reducing progressively down the line. These calcs don't addup either as the total rad output is, by calc, 9.95kw but based on the total flow and dT is 14.96kw, will have another look.
Edit: Corrected now.
JackK might just feel the boiler flow/return to get a feel for the dT (if no thermal gun) and also inform if the 17 rads are all on the one pipe or are say half on one, one pipe and the remainder on another one pipe.
Edit: Corrected now.
JackK might just feel the boiler flow/return to get a feel for the dT (if no thermal gun) and also inform if the 17 rads are all on the one pipe or are say half on one, one pipe and the remainder on another one pipe.
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