Plumbing diagram for Oil fired Pool Heater.

[Spedley]

I'm installing an old oil fired boiler to heat the kids' pool. This is my starting diagram and I'd like a bit of input please. I've not done this before and some things are counter-intuitive so I'm checking.
It is outside (in a shed) so I'll have to have anti-freeze of some kind in the system. This means it must be contained as I can't empty it down the drain. The header tank will be able to hold all the water in the system and the drain valve at the lowest point will permit pumping the water back to the header tank via a hose manually. The bleed valve at the top of the system will empty back to the header.

The pump is pumping downwards ... is that ok?
The Thermostaic Boiler Protection valve says both feeds must be near equal pressure, hence the pressure balance tap (valve to restrict flow - don't know what you call it )

Any suggestions or glaring omissions or just plain incorrect? Constructive help is much appreciated!

 

[Spedley]

Deleted

 

[oilhead]

Why should you need a 'thermostatic boiler protection valve' ?
Your boiler will have a control and limit thermostat, and should be controlled by thermostats on the pool flow or return pipework.

 

[Spedley]

Sorry, jumped in without background. Continuing this thread about boiler return feeds. https://www.diynot.com/diy/threads/can-someone-explain-return-temps-to-me.500169/#post-4132331

The pool will take all the heat from the feed and the return temp will be much to low causing condensation and boiler damage.

 

[oilhead]

What rating is the heat exchanger? If boiler is matched to that, then return temp should not be a problem.

 

[Spedley]

It's diy, nothing is matched to anything, it's all based on availability of 2nd hand parts. As it happens, the heat exchanger is about right, however the flow rates through it for the pool and heating will not be correct as these depend on pumps I already have and my pool will be hotter than a commercial pool so calculations will differ.
A valve is cheaper, easier and more flexible for differing conditions.

 

[Terrywookfit]

Forget the "Bleedtap" and use 22mm for the cold feed / expansion, teed into the vent pipe..........Or within 150mmm on flow.

Good idea to fit TMV to keep return temp up and avoiding Back end rot. !!

 

[Spedley]

Super idea, didn't think of that at all but now you mention it I do need a valve to close off the header tank. Oops!

I'd love to double thank this! Bleeding back into the header will ensure no air is ever in the system. Less than 150mm before the pump is the kind of info that you don't know as a DIYer and could have just saved me a lot of unknown problems in the future.

 

[Terrywookfit]

Super idea, didn't think of that at all but now you mention it I do need a valve to close off the header tank. Oops!

Any valve should be on the cistern inlet not outlet.

 

[Spedley]

Any valve should be on the cistern inlet not outlet.

The heater is outside so I will have to have some kind of anti-freeze in the water which means it has to be contained and can't be put down the drain. When I drain it I will manually pump it from the bottom of the heat exchanger back into the header tank which won't have a cistern but will be manually topped up.
Because of this I need to be able to isolate the header tank from the system.

 

[Terrywookfit]

If the system has correct antifreeze dosing....why would you need to drain it ??
Fernox and Sentinel c/h antifreeze can be flushed to waste.

 

[Spedley]

If the system has correct antifreeze dosing....why would you need to drain it ??
Fernox and Sentinel c/h antifreeze can be flushed to waste.

I had no idea there was such a thing as anti-freeze for central heating, I was going to use automotive. That will save me a lot of research so I'll change my plans accordingly!

Thanks!

 

[Spedley]

*Deleted*

 

[Spedley]

What rating is the heat exchanger? If boiler is matched to that, then return temp should not be a problem.

Many apologies, I thought you were way off as I bought all the parts at random but it turns out you are right ...

Heat Exchanger Spec
31 Gph Pool
11 Gph Feed
130,000 BTU
82'C Input
71'C Return (calculated)

My system
36.5 Gph Pool MAX
12.5 Gph Feed MAX
135,000 BTU boiler output (or can be run at 175,000)
85'C Output MAX
60'C Return MIN

Pretty much spot on!

 

[Spedley]

Here is the updated drawing with all the input so far and a slight change removing the Thermal Mixer Valve (Boiler Protection) which are expensive! I've left the Valve which was to regulate pressure to adjust flow to compensate for slight errors in my calculations (just in case return is slightly cool) although I may put a Thermal Circulation Valve in there as they are quite cheap and allow the boiler to heat faster (although I've only just heard about them!)