Two pumps on a heat only boiler quotation

[JackK]

I just had a quote for a new boiler install as follows

I dont undertand why a 15-60 boiler pump is needed and a 25-100 pump is needed as well

I currently have an ideal mexico 2 heat only boiler - It has one DAB pump on the boiler return and a 2 port valve at the flow pipe to allow for heating of the hot water cylinder

What am I missing to trust thhis enginner?

To change the boiler, install Vaillant magnetic filter.
✓ Vaillant EcoTEC Plus 438
✓ Vaillant horizontal flue
✓ Vaillant magnetic filter
✓ run new condense pipe to outside
✓ reconfigure pipework for hydronic separation
✓ install new Grundfoss 15-60 pump for boiler
✓ install new Grundfoss 25- 100 pump for heating system
✓ system inhibitor
✓ Registration of the new boiler with Gas Safe
✓ Registration of the boiler with Vaillant
✓ 10-year warranty with Vaillant (annual service required)
TOTAL : £5000 plus VAT
ADDITIONAL:
Should we be able to separate hot water and heating, we will need to add the
following
✓ 2x 28mm Honeywell zone valves
✓ Vaillant wired weather compensation sensor
✓ Vaillant load compensation SensoHOME room thermostat
✓ Vaillant wiring center.
✓ Re wire your heating system for new controls
✓ Registration of the boiler controls with Vaillant
✓ 10 years warranty on the controls
TOTAL: £850 plus VAT

 

[MNW67]

Sounds like one pump is to send the water through the boiler and the other to send it around the radiators and cylinder. With modern boilers, it can take a lot of pump power just to push the water through the boiler. So sometimes two pumps are used. That is probably what "reconfigure pipework for hydronic separation" means. It may involve a low loss header.

 

[Johntheo5]

If hydronic separation is required then surely another 15-60 pump is quite adequate since the main "advantage" of a LLH is that one pump takes care of the boiler HEX loss and the secondary pump circulates through the system and deals with those head losses.
Depending on the number/output of the installed rads/UFH etc then its quite possible that a 8M pump (like the UPS2) which would still leave 4M to deal with the system losses after the boiler HEX without any need for a LLH or CCTs which may be the proposal because there is no mention of a LLH in the quotation.

 

[dilalio]

Hydronic separation comes in several methods.

LLH (low loss header)
PHEX (plate to plate heat exchanger)
CCTs (close coupled Tees)

I would ask which they are considering and why.

A PHEX keeps the 2 water circuits completely separate whereas the other 2 do not.

It may be that your radiators and connecting pipework is old and therefore potentially sludged up and they do not want to risk this contaminating the boiler HEX and also keep the system side open vent so as to not pressurise old pipework that could spring leaks.

Methods of hydraulic separation for heating systems

When it comes to refurbishments, it is important to protect new equipment. This can be done by hydraulically separating the primary and secondary circuit. We look at different methods to achieve this.

hamworthy-heating.com

 

[BlueLoo]

5 ****ing grand?

 

[JackK]

Just to point out - This is for a heat only vented system - I still do not understand why two pumps are neeeded when I currently have one pump which does the job! I agree the ideal mexico 2 boiler is old but I was thinking it would be a swap out for a new heat only boiler with a pump change at the same time

 

[JackK]

I have a DAB VA 65/130 pump at the moment - Grundfos website states a UPS3 pump is a replacement - Should I really go for that or for the more expensive UPS2?

Somewhere I was reading a UPS2 has a bigger impeller and therefore better for older systems which might have sludge or dirt

 

[dilalio]

Just to point out - This is for a heat only vented system - I still do not understand why two pumps are neeeded when I currently have one pump which does the job! I agree the ideal mexico 2 boiler is old but I was thinking it would be a swap out for a new heat only boiler with a pump change at the same time

Get 2 other quotes.
Ask a friend relative if they have someone they can recommend.

 

[Johntheo5]

I have a DAB VA 65/130 pump at the moment - Grundfos website states a UPS3 pump is a replacement - Should I really go for that or for the more expensive UPS2?

Somewhere I was reading a UPS2 has a bigger impeller and therefore better for older systems which might have sludge or dirt

The Vaillant HEX will have a far higher head loss than your old Ideal Mexico one has but that doesn't automatically mean you need a LLH or whatever, if a LLH or a PHEX is the recommendation then they havn't quoted for either, how many rads have you?.
If one pump only is required then, depending on number of rads, you may require a 8M pump, the UPS3 while a very powerful pump has a max head of ~ 6.4M.

 

[JackK]

The Vaillant HEX will have a far higher head loss than your old Ideal Mexico one has but that doesn't automatically mean you need a LLH or whatever, if a LLH or a PHEX is the recommendation then they havn't quoted for either, how many rads have you?.
If one pump only is required then, depending on number of rads, you may require a 8M pump, the UPS3 while a very powerful pump has a max head of ~ 6.4M.

Thank you - I dont quite understand the head loss - Its in a two storey house with a loft so the house is about 6M high - I do have three inch steel barrell pipework rather then copper pipes.

I have 17 radiators which are cast iron

I want to replace odeally with an intergas ov hre boiler and replace the pump as well - Do I really need a 8M pump or us the ups3 ok?

EDIT : I really dont want a lowloss header or anything fancy - I want a simple replacement for an Ideal Mexico 2 boiler

 

[dilalio]

I want a simple replacement for an Ideal Mexico 2 boiler

Good luck with that!
SE long gone.
All energy efficiency now.
So... Restrictive boiler internals and you have large bore rad system an quite a few big old rads!

 

[Johntheo5]

Thank you - I dont quite understand the head loss - Its in a two storey house with a loft so the house is about 6M high - I do have three inch steel barrell pipework rather then copper pipes.

I have 17 radiators which are cast iron

I want to replace odeally with an intergas ov hre boiler and replace the pump as well - Do I really need a 8M pump or us the ups3 ok?

EDIT : I really dont want a lowloss header or anything fancy - I want a simple replacement for an Ideal Mexico 2 boiler

The head loss is the pressure loss in the pipework, boiler heat exchanger, radiatore etc, the height doesn't matter, what goes up must come down, you can see from the boiler pressure loss graph in post #2 that the head loss is over 4M at the sort of flowrates that you might require if the 17 rads are all on together, this leaves say 2.4M (UPS3) to circulate this flow through the rads etc, a fairly tall order IMO, you would probably require 3.5/4.0bar, which the 8M UPS2 will comfortably provide.
Have you a one pipe system with that huge 3" pipework?.

 

[JackK]

The head loss is the pressure loss in the pipework, boiler heat exchanger, radiatore etc, the height doesn't matter, what goes up must come down, you can see from the boiler pressure loss graph in post #2 that the head loss is over 4M at the sort of flowrates that you might require if the 17 rads are all on together, this leaves say 2.4M (UPS3) to circulate this flow through the rads etc, a fairly tall order IMO, you would probably require 3.5/4.0bar, which the 8M UPS2 will comfortably provide.
Have you a one pipe system with that huge 3" pipework?.

Thanks - Yes I have a one pipe system - Does that improve the amount of "head loss" I need?

System worked fine with a DAB VA pump so do I go for the UPS2 or UPS3?

 

[Johntheo5]

The head loss in the "one" pipe will be very very low but as the rads are running in parallel with that pipe then I think it would be prudent to install the 8M UPS2, it can allways be run at a 6M (or 7M) head if sufficient and the extra cost of say £200 isn't a fortune bearing in mind that you will be spending ~ £4000 in any event?

 

[MNW67]

I still do not understand why two pumps are neeeded when I currently have one pump which does the job!

I think you need to ask the installer why he has done all this. The second pump he has specified is a hugely powerful 10m head pump! Maybe there is something unusual about your system which he can advise further on.

I dont quite understand the head loss - Its in a two storey house with a loft so the house is about 6M high

The header tank provides the head of pressure to keep all the radiators full. The pump is just circulating the water through the system, not actually pushing it upwards.